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Our Microbiota: Critical to Our Health*


Trillions of microorganisms live in and on our body. A symbiotic relationship exists between them and our human cells. Ultimately, we are these microorganisms, and they are us. We could not survive without them, and vice versa, for many of them. The microorganisms in our digestive tract are called our "gut microbiota." Most reside in our large intestine. They are critical, as science is discovering, in one way or another, to almost all of our physical and mental functions. They need large amounts of indigestible carbohydrates, such as fiber, which they ferment, to keep themselves diverse and healthy. If they're diverse and healthy, then we're healthy. Indigestible carbs are found almost exclusively in plants. Therefore, eat real food, mostly plants. With that, let me segue into a shameless plug: Eat our fermented foods to get your indigestible carbs, and a probiotic boost! (More on probiotics and the health benefits of fermented foods in the post, The Many Benefits of Fermented Foods.)

* Disclaimer:

This is a fairly long post, citing to numerous studies and research. The intent is to clarify and inform. Educated, common sense suggestions are occasionally made. That said, none of what is written is intended to be medical advice from a licensed physician because a physician I am not. Consult a physician for medical related questions. In regards to deciding what to eat, however, you might consider educating yourself and using common sense, in light of the fact that most doctors know little to nothing about food, diet, or nutrition. With that said, let's get fermenting...


● Microbiota and Our Bodies: A Symbiotic Relationship

● Microbiota vs. Microbiome

● Trillions of Microorganisms, Millions of Species

● A Microbiota for Every Region

● Our Skin Microbiota

● Our Gut Microbiota

  • Our Gut Microbiota Process and Ferment What We Ingest

  • Indigestible Carbs: Our Gut Microbiota's True Love

  • Short-Chain Fatty Acids (SCFAs): Our Microbiota's Gift to Us

  • Our Gut Microbiota: The Command Center

  • Our Gut Microbiota: The Endocrine Organ

  • If the Gut Microbiota's Not Happy, Ain't Nobody Happy

  • Keeping Our Gut Microbiota Happy

  • Antibiotics and Our Gut Microbiota

  • Feed The Microbiota What It Needs: Indigestible Carbs

​ In Defense of Our Microbiota: Dispelling Myths About Carbs

  • Carbs Do Not Cause Weight Gain Simply Because They're Carbs

  • Low-Carb vs. Low-Fat? It's a Draw

  • A Calorie Is a Calorie...Sort of

    • Macronutrients and Net Metabolizable Energy

    • Whole Food vs. Refined Food

    • How Ingested Macronutrients Become Body Fat

  • Whole Grains Are Good, Refined Grains Are Bad

  • The Gluten-Free Fad

  • The Lectin-Free Fad

  • The Phytic Acid and Saponin Fear, a.k.a., "Anti-nutrients"

  • Ancestral-Diet-Fad Claims Against Carbs

    • Evolution and the Human Diet

    • Adaptability: The Main Takeaway From the Diets of Our Ancestors

​ When Fat, Protein, and Refined Carbs Are Substituted for Whole Plants 

​ Bringing It All Together: So Complicated, Yet So Simple

​ Eat Our Fermented Foods. Do It For Your Microbiota!

Microbiota and Our Bodies: A Symbiotic Relationship 

Scientists estimate the first single-celled organisms, i.e., microorganisms, developed around 3.5 billion years ago. Around 800,000 million years ago, some single-celled organisms got together and began trying out mutually beneficial groupings that developed into multicellular organisms. Multicellular organisms, such as humans, evolved together with microorganisms for millions of years, resulting in symbiotic relationships where resident microorganisms became more specialized to life with their multicellular "host," and vice versa. In other words, each became critical to the other's survival. In fact, the energy-producing mitochondria that are found inside the cells all plants and animals were once a type of bacteria that were engulfed by, and incorporated into, nucleated cells billions of years ago, creating a symbiotic relationship that helped bring about multicellular plants and animals. 


Microbiota vs. Microbiome

It has only been since 2001 that scientists actually began to really look into and appreciate the importance of our resident microorganisms. The human body is colonized--inside and out--with trillions of microorganisms, consisting mostly of bacteria, but also archaea, microeukaryotes (e.g., fungi), viruses, and bacteriophages. Taken together, these microorganism are called our "microbiota." Each, individual microorganism in our microbiota has its own genome (set of genetic material). The genomes--genetic material--of the entire microbiota, taken together, are called the "microbiome." (You will notice many people misusing the words microbiome and microbiota, or interchanging them. But now you know better!)


Scientists describe the human body as a "superorganism" due to the fact that we have multiple genomes: two genomes are inherited from our parents and the other is the genome of our microbiota. Our inherited genomes include the human cell genome--half from mom and half from dad--and the mitochondrial genome, which is inherited through mom's egg cell. We begin acquiring our microbiota and, therefore, our microbiome, from our mom, at birth--literally

Trillions of Microorganisms, Thousands of Species 

Recent studies estimate the number of microorganisms in our microbiota to roughly equal the total number of human cells, i.e., a ratio of 1:1. (You will likely see statements everywhere that microbiota/bacteria cells outnumber human cells 10:1. This is now deemed incorrect. This ratio was based on a poor, 1977 estimate that kept getting repeated over the decades--over 1,000 cites in scientific literature.) We don't notice bacteria and other microorganisms because they are, with a few exceptions, much, much smaller than human cells. 


Determination of the number of unique species of microorganisms making up the microbiota, however, is very difficult. Recent advances in gene sequencing technologies, however, are allowing for more accurate measurements. Recent studies suggest at least 10,000 different species are on and in the human body, with over 2,000 currently discovered in the gut. The other difficulty in determining the number species is the dynamic, open nature of the skin and gut. The digestive tract, for example, is an open system, with microorganisms coming in via food, drink, and air, making it somewhat difficult to determine which bacteria are residents, and which ones are transient.


The main difficulty in pinning down the number of species, however, is due to how bacteria propagate and share genetic material, which leads to issues as to what defines a "species" of bacteria. Bacteria reproduce by fission--dividing into two, identical cells. How they achieve genetic diversity then is the interesting part that makes them hard to categorize. Bacteria (and archaea) can "swap", pick up, or create new DNA sequences through numerous pathways, including implantation via viruses (bacteriophages), swapping DNA during direct contact with another microorganism, "mobile-element-mediated insertions," absorption of free-floating DNA, mutations, and DNA rearrangement. The possible genetic variation and ability to mutate and change is staggering. (No wonder our misuse of antibiotics has resulted in bacteria evolving resistance.)


That said, although there is a vast, unknown number of bacteria and other microorganisms on earth, the co-evolution of microorganisms with the human body and human cells has, due to specialization, resulted in relatively few species, but a high number of sub-species, in our resident microbiota. Our various microbiota are uniquely evolved to inhabit their niche within, or on, our bodies, thereby keeping our human cells safe by out-competing, and sometimes killing, outside and potentially harmful microorganisms.  

A Microbiota for Every Region 

One could say that the human microbiota is made up of two, major microbiotas: one is on the outside, entailing the entirety of our skin and orifices (nose, ears, vagina, etc.), and the other is on the inside, entailing our digestive tract, from mouth to anus. Within these two microbiota, there exists further subcultures such that each part or region of our body has its own unique, specialized microbiota (e.g., feet, armpits, and scalp, or mouth, stomach, and colon). Heck, if we just take our mouth as an example, about 700 species of bacteria have been discovered. These species create numerous, distinct colonies within our mouth, each with distinct characteristics, each uniquely evolved to live on that area of the cheek or tongue or tooth, and each interacting with each other and the host (us!) in ways that we have only begun to understand. Science is just beginning to realize how critical our resident microorganisms are to our health, mood, digestion, and physical and neural development; the interactions are staggering. Because of its importance, some scientists call our microbiota the "forgotten organ." I wouldn't call it "forgotten," however, because to forget something, you must have known about it. Perhaps the "newly-discovered organ" is more appropriate.

Our Skin Microbiota

Before we discuss the gut, let's briefly discuss our skin microbiota. It's part of our defense shield. Bacteria covering our skin protect us from harmful bacteria, i.e., pathogens, by helping produce an acidic pH of around 5 on the skin's surface, which inhibits the growth and infestation of harmful bacteria. Other bacteria in our nose, for example, protect us against infection from outside pathogens. Another recent and interesting discovery about our skin microbiota is that each person has their own, distinct microbial cloud surrounding them--a microbial "fingerprint," if you will--such that researchers could determine who had just walked into a sterilized room by analyzing the microbes they left behind. (Think of Pig Pen, from the Peanuts Cartoons, except this "cloud" is microorganisms, not dirt!)


Our Gut Microbiota

Here's where the magic happens! All humans have essentially the same variation of gut microorganisms (with some variation among individuals and populations thought to be due to environment, genetics, and diet). Any one person's gut microbiota, however, can be labeled as being one of three enterotypes, which are based on the dominant genus of bacteria in that person's microbiota. A change in enterotypes is caused primarily by diet changes. What we eat can rapidly change the makeup of our gut microbiota because what we ingest, or don't ingest, favors or disfavors the growth of certain microorganisms in our digestive tract. As this study showed, a stark change in our microbiota can be seen when test subjects are put on, for example, a plant-based or an animal-based diet. Also interesting is the fact that our microbiota are compositionally similar to that of great apes, such as chimpanzees. In fact, the gut microbiota of all great apes (the taxonomic group, Hominidae)--of which humans are one species--can be traced back to their common ancestor, which lived 15 million years ago. 


     Our Gut Microbiota Processes and Ferments What We Ingest

Our digestive tract is inhabited with microorganisms, from mouth to anus.  For example, bacteria in our mouth begin the conversion of nitrate into nitrite (when nitrates are obtained from plant sources). Nitrite is a precursor for nitric oxide, meaning our body converts it, via a chemical pathway, into nitric oxide. Nitric oxide is used by our bodies to control blood pressure via dilation of our blood vessels. When it comes to food processing, however, the microorganisms in our large intestine, i.e., colon, do the heavy lifting, or, rather fermenting.


Most of the gut microbiota reside in the colon where there is little to no oxygen. They break down food that enters the colon primarily via anaerobic ("without oxygen") fermentation. It is estimated that gut bacteria provide up to 10% of our energy needs via fermentation. In addition, our gut microbiota synthesize Vitamin K, biotin, vitamin B12, folic acid, and thiamine. Our gut bacteria also breakdown proteins into various molecules and amino acids, providing food to each other or providing beneficial molecules for the human body, some of which we'll go over below. Gut bacteria metabolize and chemically modify bile acid excreted by the liver into about thirty variations that then have varied affects on our metabolism. Our gut microbiota also metabolize and modify polyphenols, making them more bioavailable, i.e., "usable," for our body. Polyphenols are a type of phytochemical found in plants. There are now over 8,000 known polyphenols. The scope of the effect of plant phytochemicals on the human body and our microbiota is far from fully understood, but research shows that they have an incredible array of benefits such as being powerful antioxidants and cancer fighters.


     Indigestible Carbs: Our Gut Microbiota's True Love

The gut microbiota "feed" primarily on indigestible carbohydrates via fermentation. Carbohydrates come in a multitude of forms. Larger, more complex carbs are called oligosaccharides (e.g., raffinose and stachyose from beans and legumes) and polysaccharides (e.g., fiber, glycogen, indigestible starches). The difference is primarily based on the number of saccharide chains that the carbohydrate molecule contains. Our upper digestive system (mouth, stomach, small intestine) does not produce enzymes that can break down these large carbs, hence the term "indigestible carbs." These indigestible carbs have been given the name "prebiotics" * (not to be confused with probiotics).


Because our body's digestive system cannot break them down, these indigestible carbs stay intact and keep things moving and regular, so to speak, taking the "indigestible carb train" all the way to the colon. The amount of time food remains in our digestive tract is called fecal transit time. Fecal transit time is a key indicator of colon health. One sees a slowing of fecal transit time, i.e., more time between bowel movements, on high-fat and high-protein diets that lack indigestible carbs. Longer times in the colon allow increased time for some bacteria to create large amounts of carcinogenic by-products via animal protein fermentation, which has been linked to colon cancer and other diseases.


Once these indigestible carbs hit our large intestine, our gut microbiota, with a litany of enzymes, are able to break down, and feed on these large carbohydrates via fermentation. Our gut microbiota have evolved specifically to feed on these large carbohydrates. For example, one type of bacterium in our gut has been discovered to be able to code for 260 enzymes to break down carbohydrates whereas the entire human genome codes for only seventeen. The by-products of our gut microbiota's fermentation of these carbs are of great importance. The by-products directly benefit the human body, or indirectly benefit other beneficial bacteria, via "cross-feeding."

* Note: Based on the burgeoning evidence of how critical indigestible carbs are to human health, clever supplement companies are now trying to sell prebiotics in a pill or powder to uninformed consumers who are looking for a quick fix. They're essentially selling you powdered plants (example). Don't waste your money. Spend your money instead on real plants, like fruits, vegetables, mushrooms, grains, nuts, or, better yet, our sauerkraut. :) You, your microbiota, and your wallet will be happier, healthier, and richer.

     Short Chain Fatty Acids: Our Microbiota's Gift to Us

Short-chain fatty acids ("SCFAs") are one of the main, and critically important, by-products resulting from the fermentation of indigestible carbs by our gut microbiota. Acetate, propionate, and butyrate are the main SCFAs. (Gut bacteria can "switch gears," but can create only small amounts of SCFAs from amino acids, i.e., the building blocks of protein, when there is a lack of carbohydrates in the diet.)

Here are some of the many ways SCFAs are critical to our health: they reduce our gut pH (making it acidic), which makes it inhospitable for pathogenic bacteria and also increases absorption of some nutrients; they are food for other beneficial bacteria that cannot break down the indigestible carbs; most make their way to our liver where they are metabolized into components that are used to create lipids (fats) and glucose; they have been observed to protect against the development of colorectal cancer; butyrate, specifically, has been shown to promote proper colon contractions, to reduce inflammation, increase visceral irrigation, induces apoptosis, and inhibits tumor cell progression; they regulate our metabolism by being integral in helping the liver maintain glucose levels, as well as regulating our appetite and fat breakdown; butyrate helps regulate our immune system and inflammatory response; and butyrate feeds the epithelial cells that line our gut, allowing the cells to maintain a healthy gut barrier that selectively allows in nutrients, but keeps out toxins and pathogens. 

     Our Gut Microbiota: The Command Center

Interconnected with its fermentation of our food and synthesis of crucial nutrients, our ecosystem of microbes has an incredibly wide impact on our immunity, mood, and overall health, as was briefly discussed in regards to SCFAs. The gut microbiota, for example, actually has a direct effect on our skin microbiota, such that when our gut microbiota is unhealthy, we are subject to skin diseases. This newly-discovered connection is called the "gut-skin axis." A much more understood axis is the "gut-brain axis." The gut is connected to the brain via the vargus nerve such that there is bi-directional communication between the gut and cognitive and emotional centers of the brain, linking gut health to a myriad of mental and cognitive issues. Our understanding of this connection is just beginning. Here is an extremely interesting and well-done video on new research, mostly in mice, showing how mood and personality can be directly affected by the microbiota. Other axes/connections with our gut microbiota are being discovered, such as the "gut-lung" and "gut-liver." After a certain point, one has to ask, "What the heck is not affected by our gut microbiota!?"


     Our Gut Microbiota: The Endocrine Organ

Scientists also call our microbiota an endocrine organ due to the numerous hormones and hormone precursors it produces, such as serotonin, dopamine, and noradrenaline, which affect numerous things such as mood, stress, and brain function. For example, our gut microbes produce over 90% of our body's serotonin. Serotonin is critical in a myriad of functions and behaviors such as enteric motor and secretory reflexes, platelet aggregation, immune responses, bone development, cardiac function, eating, sleep, circadian rhythm, and neuroendocrine function. 


     If the Gut Microbiota's Not Happy, Ain't Nobody Happy

It is not surprising then that when we suffer from "dysbiosis"--an unhealthy and out-of-balance microbiota--our physical and neurological health suffers. We are, on some level, our microbiota. When they're not well, we're not well. Numerous diseases and conditions are linked to decrease in bacterial diversity or increases in certain types of bacteria. The chemical inter-connectedness created and triggered by our microbiota is too great and wide-ranging to discuss in any detail, but lets list some of the things that go wrong when our microbiota is not healthy and diverse. A healthy gut microbiota helps protect us from pathogenic, i.e., "harmful," bacteria, and does so while working in unison with the mucus layer that covers our digestive tract. Healthy microbiota development in our early years of childhood has been shown to be critical to the development of our immune system and our susceptibility to diseases later in life.  An unhealthy gut microbiota has been linked to autism, dementia and Alzheimer's, irritable bowel syndrome ("IBS") and IBS-associated anxiety and depressionliver diseases, gastric cancercolorectal cancerobesity, type 2 diabetes, and asthma and allergies. A recent study shows a direct link with the diversity of our gut microbiota and fatty liver disease. Fatty liver disease can be detected via an acid produced by a type of bacteria that breaks down amino acids in our food. The more advanced the disease, the less diverse our gut microbiota, and the higher the levels of the acid and the bacteria that produce the acid. 


     Keeping Our Gut Microbiota Healthy

If you've read this far, I'm guessing you have a "gut" feeling that you need to keep your microbiota, especially that of your gut, happy and healthy! But how? Well, there are many factors that affect the health of our microbiota. Exercising, for example, has a beneficial effect on our microbiota whereas toxins in our environment or food will, obviously, have a deleterious effect. Unfortunately, some things that affected your gut microbiota were out of your control: whether your mother had you via a vaginal or cesarean birth; whether she bottle or breast fed you and for how long; the amount of antibiotics your parents gave you at your doctor's behest or their pleading; and, your age. The two, main factors, however, that we as adults can control to protect and nurture our microbiota are, luckily, probably the most important: take antibiotics only when essential and absolutely necessary, and eat a diet comprised ideally of mostly whole-plant foods. Here's why.


     Antibiotics and Our Gut Microbiota

Antibiotics are life-savers in many situations. The problem is that doctors have long over-prescribed and mis-prescribed antibiotics, and patients have often mis-used them. This has led to an antibiotic crisis. The main problem with antibiotics, specifically broad-spectrum ones, is that they kill good bacteria as well as the bad ones. Not only can antibiotics devastate our good bacteria, but scientists have only recently discovered that our gut microbiota sometimes never fully recovers from the damage.  The harm caused by over- and mis-use of antibiotics can lead to a compromised immune system, causing long-term havoc (some scientists point to the allergy crisis). Antibiotics have also been shown to increase DNA mutations in bacteria, meaning the more we misuse them, the better chance bad bacteria will become immune. 


Here are some take-away suggestions that you may want to consider, in regards to antibiotics: educate yourself on antibiotics; do not take antibiotics unless you confirm with your doctor that you, or your children absolutely need them (e.g., antibiotics work on bacteria, not viruses, meaning antibiotics do not work on most colds and the flu, which are viral--not bacterial--infections); and take the entire prescription, i.e., don't stop when you think you feel better. Finally, if you want to help curtail the antibiotic crisis, reduce or stop eating factory-farmed animal products, where the animals are often fed small, daily doses of antibiotics to increase growth rates, which results in antibiotic-resistant bacteria that then enter the environment and the food supply, resulting in increased sicknesses and deaths.  

A stressed and unhealthy microbiota, perhaps after an antibiotic treatment, can often be successfully treated, fully or partially, with probiotics and fecal transplants. As for fecal transplants, they've proven very effective and, well, they're exactly what you think--taking fecal matter from a healthy individual and putting it into the colon of the sick individual to re-populate their gut with good microbes. Probiotics are food supplements consisting of a selection of bacteria that, ideally, help re-populate gut bacterial populations to create a diverse, healthy gut microbiota. Check out this article, regarding the efficacy of probiotics in treating IBS, and another study regarding the use of probiotics, generally. And as scientists' understanding of our gut microbiota increases, the ability to create more effective probiotics increases. That said, consult your doctor (preferably a gastroenterologist) and do your homework before taking probiotics. There is an every-changing, myriad of products out there, with a myriad of bacterial combinations and, since the supplement industry is unregulated, products often do not contain what they claim.


    Feed The Microbiota What It Needs: Indigestible Carbs

Finally, we come to arguably the most important factor in our microbial health: diet. As stated near the beginning of this section, the microorganisms in our colon thrive on indigestible carbs. These are found, for all intents and purposes, exclusively in plants. There are two exceptions.


Animal muscle contains glycogen, but the muscle needs to be eaten soon and raw (cooking degrades the glycogen). Once an animal is slaughtered, enzymes in the muscle tissue break down all glycogen into lactic acid within 24 hours. Another animal product that contains carbohydrates is mammalian milk, which contains the simple sugar, lactose, and various oligosaccharides, which are longer chained carbs. Human breast milk contains lactose and over 200 oligosaccharides, which are critical for the development of a baby's gut microbiota and immune system. After being weaned, most human infants forever lose the ability to digest milk. Only about 25% of the world's population has a genetic mutation, giving them continued ability to break down lactose into adulthood, allowing them to continue to consume milk. (Fermenting milk to create cheeses, kefirs, yogurts, and other fermented milk products results in microorganisms consuming the lactose thereby creating a product that lactose intolerant people can tolerate.)


Bovine milk, although obviously different in critical ways to human milk, contains lactose and trace amounts of about 40 oligosaccharides, with only 13 matching those in human milk. To cash in on the new research regarding how critical human breast milk is for early development of the human infant's gut microbiota--specifically the oligosaccharides in mother's milk--the dairy industry is trying to find ways to extract these oligosaccharides from cow milk for human, infant formula, and then patenting these methods.  

The point being that in order to have a healthy gut microbiota we need to ingest large amounts of indigestible carbs. This means we need to include large amounts of whole plant foods in our diet. 



In Defense of Our Microbiota: Dispelling Myths About Carbs

Now, as you read that our microbiota needs indigestible carbs, some of you may be thinking something akin to the following: "But carbs are the source of all evil, aren't they!?" Short answer is, "NO!" Many people are confused by the noise of numerous diet fads and diet gurus out there who claim that carbs are bad, that certain foods high in carbohydrates, such as grains, and pulses, i.e., dried legume seeds (e.g., peas, lentils, peanuts, soybeans) are bad, or even that many fruits and vegetables are "unhealthy" because of claimed "anti-nutrients." Invariably, almost all of this is misinformation, parroted by uninformed bloggers and diet gurus who cite other uninformed bloggers and diet gurus.

One problem is that "low-carb" diet fads tend to vilify all carbs, or, after all the noise, that is the end message consumers come away with. Lumping all carbs together, and calling them bad, is misguided, at best. There is a wide spectrum of carbs, from simple monosaccharides and disaccharides (a.k.a. sugars, such as fructose and sucrose) to large polysaccharides such as indigestible starch and cellulose (a.k.a. fiber). There is also a world of difference between "refined carbs," which are just highly-processed foods--grains usually (e.g., white flour)--and whole, unrefined plant foods (e.g., rolled oats). 

The result of all of this "nutrition noise" is confusion and claims of quick fixes that are monetized by the selling of books, diet plans, "advice," and/or supplements. For the good of your microbiota, we need to dispel these myths about carbs. 


     Carbs Do Not Cause Weight Gain Simply Because They're Carbs

The main way that carbs are vilified is the claim that they are directly responsible for weight gain. This is patently false for numerous reasons that we'll go into. The concern about body weight is certainly justified in light of the obesity epidemic. Almost 70% of Americans are, at the least, overweight, with almost 40% being obese. Diet gurus monetize this obesity epidemic by claiming carbs are the main cause of obesity. (Other gurus vilify fat.) If it were only so simple. The truth is, however, that carbs are not, per se, to blame. The problem is total calories. Blaming carbs (or fats) is comforting, however, because it takes the blame away from the real problem: ourselves and our poor diets, overeating, and lack of exercise.

It is a fact that Americans are eating 23% more calories today than we did in 1970. This is why we are still gaining weight--more calories in. Where are these extra calories coming from? One obvious answer is overeating processed foods that are high in added sugars, fats, and salt. About half of these extra calories are coming from, in equal measure, carbs and fat, primarily in the forms of refined grains and added oils. These refined carbs and oils, and the processed foods in which they are found, are calorically dense, but void, or severely lacking in, essential minerals, nutrients, and, most importantly, fiber. But we are also getting more fat from sources that we may not realize. For example, Americans are eating twice the amount of chicken we did in 1970. The size of chickens has doubled since then as a result of selective breeding and antibiotic mis-use. In achieving the explosion in size and growth-rate of chickens, the fat content of the chicken meat (see Table 1) is now 25% more than it was in 1970 and 34% more than 1870. Chicken now provides us with more calories from fat than from protein.


In addition, we are burning less calories--less calories out. There is an increase in sedentary behavior in front of screens whether at work or in our free time. Kids spend less time playing outdoors, and adults are more likely to have a sedentary job rather than manual labor jobs such as in factories, on construction sites, or on farms. More calories ingested and less physical activity equals the body naturally storing the extra, unneeded calories as fat. It is that simple.

Simply said, weight gain, is--barring a medical condition--simply a matter of calories in, calories out. Here is a well-done TED Talk on the matter. The equation is, in its simplest form, as follows: total calories ingested minus total used and lost. If, for example, we train like Michael Phelps, then we can eat 12,000 calories a day where dinner alone could include one pound of pasta, a large pizza, and a thousand calorie energy drink. So many carbs, yet he was not fat. It's not a mystery as to why--he burned the calories off via intense exercise. (There is a distinction, however, as to how calories are packaged, which will be discussed shortly!) Why do obese people suddenly shed weight when they have gastric bypass surgery where their stomach is reduced to the size of a walnut? Is it because they reduce carb or fat intake? No. It is because they've been forced to reduce their calorie intake due to the drastic reduction in their stomach size.

Some of the diet gurus and "health experts," claiming that carbs, not fat, are the cause for the obesity epidemic, use the following reasoning: dietary guidelines and doctors have--for the past few decades--told us to reduce our fat intake, but people are getting fatter and fatter. These gurus assumed that people had been following dietary guidelines and eating "low-fat" diets and "low-fat" foods for decades, yet still gaining weight. The assumption was that people were replacing all of this fat with "carbs." Thus, they concluded, it must be the carbs that are the cause of all the weight gain. With a little research, however, one sees that this theory is false. The devil, is in the details, as they say, and the details indicate four things of note.


First, people in diet studies routinely under-report their fat intake. (Surprise, surprise.) See studies looking into under-reporting here and here. (One assumes shame or embarrassment as the causes of the under-reporting.)

Second, when people see "low-fat" or "nonfat" on a food label, they eat up to 50% more of that food. They eat more, thinking "low-fat" means less calories when in fact the food has the same amount of calories, if not more, than the "regular" version. They also have less "consumption guilt" when eating food labeled "low-fat," which also leads to overeating. The end result is that people eat more calories on a "low-fat" diet. 


Third, as mentioned in the second point above, "low-fat" foods have as many or even more calories as the "regular" versions of that food. The reason is that processed foods always have a balance between fat and sugar such that less of one means there is more of the other. A food manufacturer and their food scientists carefully calibrate and test for the ideal combination fat, sugar, and salt to ensure they create a food that is tasty and addictive.* Never can they lower both sugar and fat; the food would be unpalatable to the average consumer. If fat content is reduced, then the sugar content must be increased, and vice versa. What this means is that the calories are near constant or even higher in "low-fat" foods (unless sugar "substitutes" are used, which have their own issues, including links to obesity and causing harm to our microbiota).


Let's take one example: low-fat yogurt. One cup of plain, low-fat yogurt has 152 calories, with 66 calories coming from carbs and 33 calories from fat. One cup of plain, whole milk yogurt has 149 calories, with 43 carb calories and 70 fat calories. As you can see, the low-fat yogurt has more sugar than the plain yogurt, resulting in both having almost the same number of calories. As mentioned above, if a food is labeled low-fat, it almost always has added sugar, and vice versa. A fruit-flavored "low-fat" yogurt is even worse, having 238 total calories--163 from carbs and only 28 from fat.

In other words, people may be on a "low-fat" diet, but they're not eating less calories. We are currently in a "low-carb" diet fad craze. Food manufacturers are, of course, adapting to demand by removing sugar, and adding back the fat. The calories remain the same. People will eat the same amount or likely more, falsely believing that eating fat will not make them fat. In a few years, people will be wondering why "low-carb" diets failed to alleviate the obesity epidemic just like many are now wondering why "low-fat" diets didn't work. 

*Note: If you are interested in reading about the processed food industry, pick up the book, "Salt, Sugar, Fat: How the Food Giants Hooked Us," by Michael Moss.

Fourth, and most important, food consumption statistics show that fat and oil consumption has greatly increased since 1970. We're not eating less fat. We are eating more! Americans ate about 350 calories per day of fats and oils in 1970. Now we eat about 575 calories of fat and oil per day. That's 225 more calories from fat per day, or about a 40% increase. The problem, therefore, is not that the low-fat diets don't work, or that people have replaced fats with carbs. The problem is that we are not, in actuality, eating less fat; we're actually eating more. Point is, if you really want to lose weight, it is still about calories eaten versus calories burnt, with fat intake being the easiest to store as fat and the hardest to then burn


Finally, do carbs negatively affect our "energy balance" by causing us to overeat? Energy balance refers to the feeding patterns and appetite urges we experience. Theories over the decades suggested that macronutrients triggered or subdued feeding patterns and appetite in different ways, including when, how often, and how much we eat. Studies suggested that protein was the most satiating (i.e., filling) and fat was the least satiating, meaning we could eat more fat, relative to protein and carbs, without feeling full. The science had indicated we should be wary of fats. A review of all the scientific literature on the topic of energy balance, however, showed that there is no definitive difference as between carbs, proteins, or fats, as regards energy balance. There are just too many variables. The study's authors conclude: "There may be health reasons to emphasize one macronutrient over another in a diet, but from the perspective of energy balance, total energy intake, rather than its source, is the critical factor to address." There is one area of certainty, however, according to the authors: "One area of agreement is that body weight is a function of energy balance, and there is evolving acceptance that this is truly based on energy itself rather than its source. Body weight can be gained, lost or maintained on diets varying in macronutrient composition." In other words, carbs do not make people gain weight anymore than protein or fats. It's the total calories ingested that is the issue.

In sum, the low-carb, high-fat craze is nonsense. If you're still skeptical, let's look at actual studies that tested the low-carb diet against the low-fat diet.


     Low-Carb vs. Low-Fat? It's a Draw

Studies such as this one and this one show that weight loss can be achieved on either a "low-fat" or a "low-carb" or a "high-protein" diet. (Those on the "low-fat" diets, however, also had the added benefit of decreased risk factors for cardiovascular disease.) Diets described as "high-protein" appear to be only marginally more effective in weight loss. A systematic review and meta-analysis of studies on "low-carb" diets versus both high-protein and high-fat diet variations showed no significant difference between diets. As to protein, getting more of our amino acids, i.e., "protein," from plants rather than animal sources, for example, shows health benefits, aside from the very important fact that plant proteins are packaged with indigestible carbs. We know who needs and loves indigestible carbs.  

Let's now address the diet gurus who claim otherwise. Two of the most outspoken proponents of the "low-carb, high-fat" diet fad were so certain of their claims that they created an organization, the Nutrition Science Initiative, through which they would fund definitive studies that would validate their claims. They claimed that their studies would definitively prove the carb-insulin model for obesity, i.e., the "carbs-make-us-fat" hypothesis. The result of the studies where not what the gurus had hoped for. 

The main study funded by the Nutrition Science Initiative was a  large, randomized trial, with over 600 participants, conducted by Stanford researchers. The study is explained well here. In short, the study showed that people on either a "low-carb, high-fat" or "low-fat, high-carb" diet lost significant weight when they cut out processed and refined foods. (Surprise.) The study, obviously, did not support the Nutrition Science Initiative's founders; neither did a smaller, prior study, which they also funded. (For interesting reading on the downfall of the Nutrition Science Initiative and their low-carb, high-fat crusaders, here is an article and here is a detailed blog post. After these studies, one founder quietly left the organization with a large amount of money while the other has been conspicuously less vocal since the studies.)

Finally, when someone is on a low-carb fad diet, they are also--unbeknownst to them--on a low-fat diet (or at least on a "lower"-fat diet). Here's why. Foods almost always have both fats and carbs. When "low-carbers" cut out foods that they or someone has labeled a "carb," they are often also cutting out fat. For example, a low-carber stops eating donuts because they're made from highly refined grain and are often coated in a sugar icing. That donut contains 11% of your recommended daily allowance (RDA) of carbs, but it contains 18% of your RDA for fat. Take a Triscuit cracker, which looks like a square of pure carbs. Nevertheless, it has the same RDA of fat as it does for carbs.


Then take a couple examples of "carbs" that are actually mostly carbohydrates: a slice of white bread (8% RDA of carbs; 2% RDA of fat) or a plain bagel (5% RDA of carbs; 1% RDA of fat). People rarely eat such items plain, however. They are almost always topped with high-fat foods. On the bread, people add things like mayonnaise, butter, cheese, deli meats, peanut butter, hummus (made with olive oil), etc. On the bagel people usually add butter or cream cheese. All of these additions are dense sources of calories from fat. What about pasta or pizza? Sure the pasta and pizza crust are (usually refined) carbs, but then you add fat sources such as olive oil, meat balls, pepperoni, cheese, bacon, etc., which gives you a dense calorie bomb. (Plus the tomato sauces usually have calories from added sugar.) These low-carb dieters are not cutting out carbs when they forgo these foods as much as they are cutting out densie calorie sources.


The take-away point: it is neither fat nor carbs, per se, that make us fat. It is a calorie overload.

     A Calorie Is a Calorie...Sort Of

Some argue that not all calories are equal. This is--technically speaking--not true. A calorie is simply a measure of energy used in scientific fields such as chemistry to measure the heat energy required to raise the temperature of 1 gram of water to a specific level. As was discussed in the preceding sections, in regards to weight gain, the big-picture formula is simply about calories: we take in more calories than we need. That is all one really needs to know. But if we take a closer look, we see that the number of calories that we ingest does not equal the number of calories available for our body to use. How a calorie is packaged has some influence on this discrepancy.  


          Macronutrients and Net Metabolizable Energy

Although a calorie is a calorie, there is a distinction--in regards to available energy and nutrients--as to whether a calorie is "packaged" in the form of fat, protein, or carbohydrate. These macronutrients don't provide our bodies with usable calories equally. There is a difference as to the amount of energy our bodies can garner from each of the macronutrients. To better understand this, the "calories in versus calories out" equation can be broken down as follows: (calories ingested) versus (calories lost via feces, urine, and gas via microbial fermentation).

Broadly speaking, there is the ingested (gross) caloric energy, which is the total energy as calculated in a lab by total combustion of the food into CO2 and water, using a "bomb calorimeter." To then get the net energy for metabolism, you take the gross energy available and subtract it from the the amount of energy actually available to our bodies for metabolism. Roughly speaking, using the most common measurement method, a gram of either protein or carbohydrates will provide the human body with 4 calories of usable energy for metabolism whereas a gram of fat provides 9 usable calories. There are numerous reasons for this, but a few main ones. Some energy/food is neither digested nor fermented, passing through us and lost in feces. Some energy is lost in gas via microbial fermentation. Some energy is lost in urine as part of nitrogenous waste compounds as a result of incomplete protein breakdown. 

I said "roughly speaking" as regards to the net calories per gram from carbs (4), fat (9), and protein (4) because of the incredible number of measurement variables, including three slight variations in the calculation of food energy conversion. In addition, our bodies process different carbs in different ways, resulting in different net calories. Finally, different proteins have different amino acid profiles, which affects how they're processed by our bodies, which in turn leads to different net calorie calculations. If you want more detail into the analysis of net and gross calories from macronutrients, take a look at this well-done, informative, and entertaining piece on the subject. For even more detail, check out the chapter, Calculation of the Energy Content of Foods - Energy Conversion Factors, by the United Nation's Food and Agricultural Organization ("FAO").

          Whole Food vs. Refined Food

Foods are mixed packages. (Unless we're ingesting lab-made supplements, food is a mixture of carbs, proteins, and fats.) It makes a difference whether a calorie is from real, whole food or from refined, processed food. When we eat processed foods, we run into issues because the balance of nutrients has been severely altered where some nutrients have been isolated or removed. We have already discussed refined grains, where the fat and much of the indigestible carbs and minerals have been removed, leaving concentrated starch calories. Let's take another example: apple juice versus an apple.  One hundred calories of apple juice is not "packaged" the same as 100 calories of a fresh, unprocessed apple. The juice is essentially sugar water whereas the apple has lots of fiber, polyphenols, and other critical substances that the juice does not. The juice provides a quick, almost instant burst of calories whereas the apple provides a slower access to the calories due to us having to chew it piece by piece, and because of the buffering effect of its higher fiber content, which is not digested, but which is later fermented in the colon by our microbioata. This is why it is critical to eat real, unprocessed foods, i.e., foods "packaged" in their natural state, or very close to it (like our sauerkraut! :)). The "package" in which the calories are delivered, or lack thereof, is critical to our health, including our microbiota. 


          How Ingested Macronutrients Become Body Fat

In addition to the importance of how a calorie is packaged, there is a clear difference in how our bodies burn and store calories from protein, fat, and carb molecules. In regards to metabolism, our bodies oxidize, i.e., burn off, and tightly regulate excess protein and carbs because there is both a finite need and finite storage capacity for each. In addition, protein and carbohydrates are rarely converted to fat (in a process called lipogenesis) due to the energy required by the body to convert these molecules into lipids, i.e., fat.


Excess carbs are used as follows as we consume them: 1.) first stored as glycogen (in our muscles and liver); 2.) then oxidized, i.e., burnt to power our muscles, brain, etc.; and 3.) under very high carb intakes, relative to energy needs (i.e., glycogen stores are full and current energy needs met), the body will use energy to convert any remaining carbs into fat, storing the created fat in our fat cells.


Fat intake during excessive caloric consumption, however, results in the body incorporating the dietary fat directly into fat cells. This is because dietary fat is already in the form of lipids, i.e., fat; the body needs to do little conversion to shuttle dietary fat into fat cells. Also, studies show that our body has a very weak satiety point for fat. In other words, there seems to be a much weaker point of feeling full when it comes to foods dense with fat calories (as opposed to carbs or protein). This leads to passive overconsumption and weight gain. 

Essentially, all of this can be summed up as follows: When we consume more calories than our body loses and uses, our body has no need to pull out fat stores and burn them, meaning will will not lose weight. We either maintain or gain weight. Furthermore, extra calories that are ingested in the form of fat will be shuttled into our fat cells first because that is, biologically-speaking the easiest. Extra calories in the form of carbs and proteins will be converted--in a small percentage--to fat, only after our bodies use up, in the case of carbs, the majority of the excess via 1.) oxidation and 2.) conversion into glycogen, which is stored, at regulated, set levels, in the liver and muscles.

     Whole Grains Are Good, Refined Grains Are Bad

Refined carbs are the only "bad carbs." When we talk about "refined carbs" we are almost always talking refined grains, specifically wheat, corn, rice, and soy. In the USA at least, the government heavily subsidizes these four grains with taxpayer funds, resulting in cheap grains, which, in turn results in cheap ingredients for junk food and cheap feed for livestock. Taxpayers are indirectly paying for their poor health by subsidizing junk food and factory farmed animal products.*


Refined grain has the most nutritious parts of the grain removed (the "germ" and "bran"), leaving only the starchy endosperm. The germ and bran contain fat, fiber, and various other nutrients and minerals. Removing these nutrients, especially the fat, i.e., oil (which will go rancid), is good for making junk food and packaged food because doing so extends the shelf life and, therefore, increases the profit margin of the products. The removal of the fiber, fat, and and most minerals and nutrients is not good, however, for our microbiota and, therefore, our bodies. 


Americans consume large amounts of refined grains (77% more than recommended) and not enough whole grains (only 34% of the recommended amount). One likely factor in this disparity is misleading food labels. Foods labeled "whole grain" are often not 100% whole grain due to lack of standard definitions and guidelines. Manufacturers take advantage of this by using confusing labels. Guidelines in the U.S. only require >51% of grains to be "whole" in products labeled "whole grain," meaning the other 49% can be refined grains. Therefore, try to look for "100% whole grain" to get the healthiest, least refined option.


A simple, common-sense way to dispel this "grains-are-bad" myth is to try to find a long-term study showing that those who eat large amounts of 100% whole, minimally to unprocessed grains (e.g., rice, corn, oats, wheat, etc.) actually suffer from more diseases and subsequently die sooner than those who eat very little to no whole grains. Such a study does not seem to exist. On the other hand, numerous studies indicate that higher intakes of whole grains are associated with a decrease in all types of mortality, including cancers (especially colorectal), cardiovascular disease, diabetes, coronary disease, infectious diseases, etc. (See examples of studies here 1, here 2, here 3, here 4, and here 5.) 

*Note: Sugar is also heavily subsidized. Dairy is heavily subsidized, too, resulting in the government buying and stockpiling tons of cheese


     The Gluten-Free Fad

The gluten-free craze is another diet fad that is born of misinformation. The main beneficiaries of the gluten-free craze are diet gurus and food manufacturers who, by sticking "gluten-free" on products, blogs, or cookbooks have reaped huge profits from gullible consumers who think eating "gluten free" will be a miracle cure for everything that ails them. Diet gurus misinterpret or misrepresent information regarding gluten to falsely conclude that no one should any eat grains.*


First, to be clear, gluten is dangerous, IF you have celiac disease and, to a lesser degree, if you suffer from gluten sensitivity. Don't waste your money on "gluten free", or feel the need to abstain from grains and legumes unless you have been tested for celiac disease or gluten sensitivity. Less than 1% (0.75%) of the population has celiac disease,and not more than 6% might suffer from the controversial non-celiac gluten sensitivity. In fact, many people who think they have gluten sensitivity actually do not, as studies are showing. Many of these people fall victim to the "nocebo" effect (as opposed to the "placebo" effect)--where a person, through a strong belief that they suffer from a certain disease or ailment, mentally creates physical symptoms associated with whatever disease they think they have.

Second, not all grains contain gluten. Telling all people to avoid all grains, implying that all grains contain gluten, is misinformation.

*Note: As a quick example of how diet gurus and their followers mislead unwary consumers--by way of either their lack of knowledge, intent to mislead, or their confirmation bias--is seen in this post, on the website belonging to the "father" of the "Paleo diet." In an effort to argue that no one should eat grains, the author of the post states that studies are showing "increased quality of life in those who consume gluten-free diets . . . [which is] caused largely by avoiding the regular consumption of grains." Takeaway message? No one should eat any grains. If you look at the referenced study for this "fact," however, you will see--even in the study's title--that the study was based on celiac patients (not the general population) having a better life when not eating gluten. Well, duh! Obviously, if you have celiac disease, refraining from gluten will make your life better, just like refraining from peanuts will make your life better, if you have a peanut allergy! The problem is claiming that all people should avoid all grains although most people have no problem with gluten, and not all grains contain it.  

     The Lectin-Free Fad

The next diet fad seems to be "lectin-free." The no-lectin diet fad gurus claim that lectins in grains, legumes, and vegetables are bad. This, again, is misinformation. There are numerous types of lectins, naturally found in all living things (plants, animals, and microorganisms). At least 500 have been found in plants. Some, like those in raw kidney beans, for example, will make you awfully sick. But if you properly soak and cook beans, then almost all of the lectin is removed. Other groups of lectins, however, have shown to be very beneficial by, for example, fighting cancer, or acting as antivirals. Lectins have been linked to reducing glycemic indexes by slowing carbohydrate digestion. Point being, saying that all lectins, in any amount, are bad is as misguided as saying all carbs are bad. 

     The Phytic Acid and Saponin Fear, a.k.a., "Anti-nutrients"

Another chemical, phytic acid, which is found in grains and legumes, as well as nuts and seeds, is described by fad diet gurus* as an "anti-nutrient." It is true that current science shows that phytic acid binds to some nutrients (at which point it is called phytate) so that our body cannot absorb the bound nutrient. Again, like most things in nutrition, the truth is not as clear cut.


First, as with lectin, proper soaking, fermentation, and/or cooking of phytic acid-containing foods greatly reduces phytic acid content, making nutrients more bioavailable. Second, as science progresses, the myth of phytic acid being harmful is being disproved. There is a strong link between phytic acid intake and lower colon cancer rates. In addition, gut bacteria have been discovered that can break down phytate such that it releases bound nutrients; up to 100% of phytate was shown to be degraded in a healthy gut. Third, there is more than a hill of beans (pun intended) of research showing that beans and legumes (just like whole grains)--when properly cooked, fermented, or sprouted--are health promoting, being linked to a reduction in just about all causes of death and types of disease. (See examples of studies here 1, here 2, here 3, here 4, and here 5.) 

*Note: Notice how the cited diet guru makes numerous claims regarding phytic acid, but provides no citations in support of her phytic acid claims, other than one about nuts and saponins). The saponin citation, however, is to another fad diet blog, regarding another alleged "anti-nutrient"--saponin. This is typical of the diet fad world--baseless misinformation that stokes fear, which is cited over and over again by the misinformed or hucksters. Saponin, for example, like phytic acid, is a compound, of which there are numerous types. It is found in both plants and animals. Studies show saponins to be very beneficial, including having anti-viral and anti-cancer affects. 


     Ancestral-Diet-Fad Claims Against Carbs

          Evolution and the Human Diet

The "ancestral diet" fad, and its various permutations, claims that grains, legumes (beans, peas, lentils, peanuts, and soybeans), and vegetables, such as tomatoes, peppers, and potatoes, are bad for us. Some variations of this diet fad even claim we need to avoid many fruits and berries--such as apples, cherries, watermelon, blackberries, and grapes--and also nuts, such as pistachios, almonds, and hazelnuts! These diet claims are NUTS! Can you imagine our ancient "caveman" ancestors coming across grains, nuts, fruits, berries, and/or vegetables and shunning them because their ancestors a million years prior did not eat the exact same foods!? LOL! Despite common sense giving us a quick answer, let's look at the facts.


The ancestral diet fads often embrace the previously discussed carb, gluten, lectin, phytic acid, and saponin fears. The ancestral diet gurus, however, have an additional claim as to why humans should not eat grains, legumes, and some fruits, vegetables, and nuts: humans have not evolved the ability to digest these food items since we, as a species, only began eating them regularly, after the agricultural revolution, starting 12,000 years ago.


One implication of this theory is that evolution works only over long periods of time. This premise is false, however. Humans, and species generally, can evolve quickly, via what is called "rapid evolution." Humans, for example--at least certain groups--have evolved new genetic adaptations to adapt to new dietary patterns resulting from the agricultural revolution. Starting 8,000 years ago, the genetics of some agricultural populations that depended on milk and cheese for calories evolved the ability to to digest lactose into adulthood by "selecting" for a genetic mutation that allowed them to efficiently obtain calories from the milk of animals they were herding. Other populations, who became dependent on grain as a primary calorie source, developed the ability to produce more of the enzyme amylase, which breaks down starch--the energy source in grains. (Not all starch is digestible, however, as we have recently discovered. But remember that our gut bacteria can ferment these indigestible starches, i.e., carbs!)

Furthermore, humans' relationship with grains extends much farther back, and is more ingrained (pun intended), than the ancestral diet gurus claim. New evidence shows that when human ancestors came down from the trees about 3.5 million years ago, we changed from a diet of primarily fruit and leaves to eating more grasses and grains, and eating animals that fed on grasses and grains. New technologies used on dental abrasions, dental plaque, and coprolite (fossilized poop) of ancient, human ancestors, such as Neanderthals, have revealed grain consumption tens of thousands of years prior to the agricultural revolution. Some communities of human ancestors were gathering, grinding, and eating grains at least 100,000 years ago. In fact, a site was discovered in Jordan where humans were baking unleaven bread around 14,400 years ago. This is over 2,000 years before the agricultural revolution started. The bread consisted of wild grains that were ground into a paste and baked in ovens.

     Adaptability: The Main Takeaway From the Diets of Our Ancestors

Theories regarding ancestral diets are often based on misinterpretation of information from either recent hunter-gatherers or that of archaeological information. This misinterpretation leads ancestral diet gurus to falsely conclude, for example, that the bulk of calories came from meat, which they then extrapolate to be the ideal diet for the modern human. During our ancestors' long evolution into humans, beginning about 23 million years ago, large amounts of whole, unprocessed plant foods had always been a critical component of the human diet. Leaves, grasses, flowers, fruits, mushrooms, tubers, roots, berries, nuts, seeds, seaweed, and wild grains were, for obvious reasons, often more abundant, and often easier and safer to gather, than hunting animals, protecting the kill from large carnivores, and, in warmer climates, eating the animal before putrefaction set in.


As humans ventured to extreme environments they tended to get more of their calories from eating animals.

Some diet gurus point these isolated populations to show that a diet mostly of meat and animal fat, and little plant food, is healthy or even ideal. The Inuit are the most-often-used example used to support the benefits of low-carb, high meat and animal fat diets. The oft-heard claim is that the Inuit had almost no cardiovascular disease despite a diet based on meat and animal fat. Claims of Inuit health, however, have apparently been based on forty years of misinterpreting a single study--a study, as it turns out, that never looked into cardiovascular health of the Inuit. In actuality, traditional Inuit had cardiovascular disease at the same rates as other populations, a very high occurrence of death from strokes, a mortality rate twice that of non-Eskimos, and a life expectancy of about ten years less.


Yes, humans can live in extreme climates. No doubt. Those that do live in specific locations, especially extreme environments, however, are often better adapted to do so due to thousands of years of adaptation to that particular environment. The Inuit, for example, are genetically adapted to Arctic regions, having unique genes for cold tolerance and fat distribution. Another example of adaptation to a specific environment is the high-altitude, genetic adaptations of the sherpas who live in the Himalayas. So the question should not be whether humans can survive in extreme conditions. We can, obviously, especially if we have physical adaptations to do so. The question should be whether we--the rest of humanity--could thrive in those conditions and on those diets, without physical adaptations that are environment-specific. 


Scientists, such as paleoantropologists, who--in contrast to ancestral diet gurus--actually study early human ancestors, dismiss the ancestral diet fad as a "myth." Diet gurus claiming to have "discovered" what humans should or should not eat, based on ancestral evidence, are claims without merit. Wild plants and animals, and life in general, are selfish; they evolve to survive and reproduce. Plants, animals, and fungi do not evolve, on their own, to provide humans with a "perfect" calorie source. Our ancestors hunted, gathered, and scavenged food in their local habitat, always doing a cost-benefit analysis that took into account the following: their energy needs; the food's availability; the food's caloric density; the food's toxin content; the danger and/or caloric expenditure required to gather or hunt the food source; and the energy required to process it. 


The calorie sources, i.e., foods, in our ancestors' habitat changed constantly, whether over the short-term based on seasons and droughts, or over the mid- to long-term for those wandering into new ecosystems and climates, or for those who had to deal with climatic shifts, such as ice ages. Human ancestors adapted to eat just about anything in their immediate environment (e.g., bark, insects, larvae, seeds nuts, fruits, fungi, leaves, roots, and animals, via scavenging or hunting). We see this adaptability in recent studies on Neanderthal dental plaque. The research shows that some Neanderthals--our most recent and closest relative who was thought to have eaten primarily meat--actually ate primarily plants (e.g., mushrooms, pine nuts, bark, moss, etc.) when in warmer climates. Other Neanderthal groups, however, living in harsher, northern latitudes--where winters stopped most plant growth--had to find more calories from animals. 

This adaptability to eat different food sources is one of the reasons why humans ended up populating all corners of the earth. In fact, the ability to effectively find and gather high-caloric foods, i.e., foraging efficiency, is a theory regarding the expansion in human brain size. The ability to find, gather, and eat high-caloric foods meant high-level group cooperation, and the ability to find food and the ability to remember how and where to find or gather it. The theory suggests our ability to incorporate a wide-range of foods in our diet, and our focus on finding foods with higher, caloric density gave humans the extra calories to develop larger brains. The other main theories regarding human brain expansion--namely the meat consumption theory and the using fire to cook meat and plants theory--also, at their core, suppose that humans found ways to eat whatever was available. 


With the agricultural revolution, however, humans began manipulating nature to increase caloric density of foods. We bred wild plants and animals, with the main goal to make them more caloric dense. We made plants bigger and sweeter, and we made animals, for example cattle and chickens, bigger, slower, and fatter. Modern chicken meat, for example, now provides more calories from fat than from protein. In other words, unless you hunt wild meat and forage wild plants, your diet will never resemble that of our pre-agricultural-revolution ancestors.

When Fat, Protein, and Refined Carbs Are Substituted for Whole Plants 

While on a low-carb fad diet or the Standard American Diet ("SAD"), instead of a large amount of undigested carbs hitting our colon--which our gut microbiota ferment into good stuff--high amounts of protein, fat, refined carbs, or their digested by-products hit our colon. Studies clearly show, e.g., here and here, that there are numerous deleterious side effects of consuming high levels of animal protein and fat, and too little whole plant foods.


A general lack of fiber and complex carbohydrates, due to a diet filled with large amounts of refined carbs, oils, and animal products has repeatedly been shown to be linked to high rates of diseases, such as colon cancerStudies show that high-protein, low-carb diets drastically reduced certain types of bacteria in our gut along with the amount of SCFAs, a reduction which is linked to IBS and colon cancer. These diets have been shown to be unhealthy for the gut microbiota. Researchers observed that in the low-carb, high protein test group there was a large decrease in beneficial compounds, such as short-chain fatty acids, and an increase in carcinogenic N-nitroso compounds (by-products of bacterial fermentation of animal protein), which cause DNA damage and, likely cancer, over the long-term. 


As far as our microbiota are concerned, protein, from either plants or animals, does provide important things such as nitrogen. BUT, the amount of protein must be constrained to not result in a dysbiosis. (Studies indicate plant protein to be better overall than animal, which is associated with higher mortality rates.) Excessive amounts of animal protein are fermented by the microbiota into relatively large amounts of ammonia, hydrogen sulphide, amines, phenols, thiols and indoles, all of which have been shown to be cytotoxins, genotoxins and carcinogens. Another problem with high amounts of animal protein (especially red meat), relative to whole plant foods, is that the colon gets large amounts of choline and L-carnitine, both of which gut bacteria ferment into trimethylamine-N-oxide (TMAO). TMAO has a strong positive correlation to cardiovascular disease such as atherosclerosis, stroke, and heart attacks.


In addition, a high-fat diet has been shown to cause an increase in bacteria-derived lipopolysaccharides in the blood. These are a very potent inflammatory agent linked to insulin sensitivity and metabolic diseases such as obesity and diabetes. Also, when we eat a lot of fat, our liver produces more bile, which is used to break down the fat. When too much bile is produced, some escapes recycling, making its way from the small intestine, to the large intestine, where gut bacteria convert the bile into secondary bile acids. These can accumulate to high levels and may contribute to colon cancer, gallstones, and other gastrointestinal diseases. 

Earlier, we talked about how fiber and other indigestible carbs speed up fecal transit time. This helps minimize the damaging effects of the above-mentioned by-products resulting from the digestion and fermentation of protein and fat.

Bringing It All Together: So Complicated, Yet So Simple

The incredibly complicated interactions between the thousands of chemicals and nutrients in food, our complex human digestive system, and the trillions of microorganisms in our gut is, as of yet, well beyond our complete understanding. That said, human evolution over 23 million years centered around eating a myriad of different foods in their natural state where the extent of food processing included cutting, grinding, cooking, salting, smoking, and/or fermenting. These diets almost always--especially over the long-term--included large amounts of indigestible carbs via plant foods, which fueled a critical component of who we are: our microbiota. 

Although there is little to no benefit in speaking about specifics regarding diet due to individual variables resulting from things such as genetics, environment, age, etc., we can certainly speak in generalities. If we apply Occum's Razor, all we need to know is this: eat real food. The renowned food author Michael Pollan put a finer point on this simple dietary principle when he pithily stated, "Eat food. Not too much. Mostly plants." Long-term studies repeatedly show that those who eat more whole plant foods are healthier and less likely to gain weight. One can clearly see this simple advice of eating real food, mostly plants in the diets of the longest-lived, healthiest populations in the world--the so-called "Blue Zones"--where apparently 90-95% of their calories are from carbs, i.e., whole plants. What we can't do--over the long-term--is substitute animal products and/or refined, processed foods for whole plant foods. The balance of your caloric intake should be in favor of whole plant foods, for the sake of your microbiota and, therefore, for you.

Eat Fermented Foods: Do It for Your Gut Microbiota!

This brings us to fermented foods, specifically raw (unpasteurized) fermented foods. They're an ideal way to increase your consumption of the large, indigestible carbs that your gut microbiota love to ferment. Raw, fermented foods also contain beneficial bacteria (probiotics) that will feel right at home in your large intestine. Fermented foods have so many other benefits, in addition to these, two main ones. Check out the Info piece, The Many Benefits of Fermented Foods, to find out more about their health benefits. 

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