UPDATED: April 30, 2025
Welcome to the Healthy Living Is Good Medicine Newsletter, a free publication covering a wide variety of health-related topics, with timely original articles intended to help people lead healthier and more fulfilling lives.
Diet and Evolutionary Biology
Diet has shaped the evolution of humans, and studying the paleobiology and evolutionary ecology of our species can help us understand what kinds of foods had the greatest survival value for our ancestors. According to fossil evidence, DNA analyses, and studies of the evolutionary metabolome, our species has been eating a wide variety of whole foods, including both plants and animals, for more than three million years.
An ethnographic analysis of diets eaten by modern-day hunter-gatherers shows they vary substantially in their carbohydrate content, depending upon the latitude, eco-environment, and genetic adaptations of the population. For example, the traditional diet of the Inuit, a hunter-gatherer people living in the Arctic, is extremely high in animal protein and fat, with limited access to fiber-rich roots, seaweed, and wild berries during the short summer. The diet of the San people of the Kalahari Desert in Africa is determined by rainfall. Roots, tubers, and melons provide fiber, and insects and larvae are an important source of protein and fat during drier times when game is scarce.
It should be obvious that refusing to eat anything that comes from animals goes against our human nature, which has been refined by eons of evolution. Extreme herbivorous diets that totally exclude animal-based sources of nutrients, and need to address the inevitable deficiencies with manufactured supplements, cannot be considered healthy. Let's examine some of the most common diets that are followed by today’s urbanized human populations.
Wholly Plant-based Diets
It's a mistake to assume that vegetarian, vegan, or wholly plant-based diets are a healthy way to eat. Cane sugar, white bread, potato chips, and pretzels come from plants, but there is no way that they could be considered health foods. Just because a diet has no animal-based ingredients doesn't exclude junk foods and the ultra-processed foods (UPFs) that make up the majority of the typical American diet.
UPFs are industrially processed, pseudo-foodstuffs that usually contain chemical additives such as sweeteners, flavoring agents, coloring agents, emulsifiers, and preservatives. UPFs tend to be calorie-dense, nutrient-poor, highly palatable, and intentionally addictive. UPFs can even contain undisclosed amounts of industrially-produced, hydrogenated trans-fats that have been implicated in cardiovascular disease.
Common plant-based UPF examples include breakfast bars, most cold cereal including granola, English muffins, bagels, rolls, most breads, crackers, French fries, brownie mixes, coffee cake, pies, cakes, cookies, donuts, muffins, biscuits, sweet rolls, candy, energy bars and drinks, protein bars, granola bars, most apple sauce, jams, jellies, fruit preserves, ketchup, chili sauce, salsa, salad dressings, margarine, mayonnaise, soy sauce, non-dairy coffee creamers, carbonated beverages, canned and bottled juices, coffee and tea drinks, canned vegetable soups, and anything containing artificial sweeteners and most sugar substitutes.
Eating a salad or an orange won't offset the ill effects of UPFs, nor make up for consuming too much of the unhealthy, fast-food trinity; simple carbohydrates high in fructose, salty sodium chloride, and saturated fats high in calories and fat-soluble toxins. Currently available evidence indicates that ultra-processing food products can potentially compromise health and have an adverse environmental impact.
Vegetarian food patterns and cardiometabolic risk can vary as a result of other food choices, according to a recent analysis. A new study compared the microbiomes of vegans, vegetarians, and omnivores. Its findings suggest that eating a diet emphasizing plants may be more beneficial for cardiometabolic health than cutting out red meat.
A vegetarian diet that includes fruit juices, sugar-sweetened beverages, candy and sweet-treats, and high-carb desserts, increases the risk of heart disease and metabolic disorders such as obesity, fatty liver disease, and type 2 diabetes. Analysis of almost a decade’s worth of data from a large U.K. Biobank cohort found that the dietary contribution of plant-sourced UPFs was positively associated with a substantially increased risk of cardiovascular disease.
A recent study found that high sugar intake was linked to accelerated biological aging, while nutrient-rich diets such as the Mediterranean diet were associated with significantly lower epigenetic age. The study concluded that sugar has a negative impact cellular longevity. The recommendation is to increase nutrient intake simultaneously reducing sugar consumption.
Let the consumer beware: There are many food products labeled as being "vegan" or "vegetarian" that are ultra-processed and therefore unhealthy. For example, the Loma Linda brand of textured vegetable protein products, promoted as "healthy" meat substitutes, can contain industrially produced chemicals, as one can see from this list of ingredients:
The Vegan Diet
A vegan dietary pattern is the most extreme plants-only diet in existence. It prohibits meat, poultry, fish, eggs, dairy products, and honey, even in trace amounts. Veganism is a quasi-religious philosophy that vehemently opposes what they see as the exploitation of animals. The only religious test that Veganism lacks is a faith in a supernatural being (or vegetable deity).
The way you can tell the difference between a vegan and a vegetarian is that a vegan will proudly let you know who they are, without being asked. Vegans won't wear clothing made of wool or leather, or use cosmetics that have been tested for safety on animals. Reddit's “Fur is Murder” proclaims itself to be social media's largest vegan community.
Vegans oppose the use of service animals, such as guide dogs for the blind, and medical research involving laboratory animals. It should be noted that during the COVID-19 pandemic, many vegans who didn’t want to die received vaccines that they knew had been tested on animals. This goes to show how it's possible to hold two opposing ideas at the same time, and not have your brain burst into flames.
The vegan core philosophy has nothing to do with healthy eating, although vegans might claim that their diet confers almost miraculous health benefits, while at the same time starving themselves of protein, omega-3 fatty acids, and other essential nutrients. Their nutritional deficiencies are virtually guaranteed unless dietary supplements are taken, and even then, those products must be free of animal origins. In a previous Post I went into detail about the nutritional deficiencies that vegans and strict vegetarians risk, and how to best prevent them:
Historically, a number of religions have leaned heavily toward plant-based diets, such as Hindu, Buddhist, Jain, Sikh, and Seventh Day Adventist. Today, many followers of those religions take liberties with their diets without worrying about excommunication.
There isn't a single religion that rigidly insists upon total abstinence from animal-based foods. Much like the Shakers who abstained from sex, had a vegan-themed religion existed before modern times, it probably would have died out fairly quickly because its dietary and lifestyle restrictions are at odds with human survival.
Comparing a low-fat vegan diet with a healthy Mediterranean diet, a study found that vegans lost more weight, had lower blood lipid levels, and better insulin sensitivity, but they did not do as well when comparing blood pressure outcomes. There are known short-term benefits such as weight loss associated with intermittent fasting, but starving oneself is not necessarily the key to a healthy, happy life.
Dietary preferences involve an exquisite interplay among a number of factors, including family traditions, social and cultural pressures, as well as natural influences determined by genetics, including how dietary items are metabolized and their physiologic effects, and taste perception. A genome-wide association study uncovered three genes closely associated with lipid metabolism that could potentially affect a person’s ability to remain healthy on a strictly vegetarian diet.
The Ovo-Vegetarian Diet
We can easily image our paleolithic ancestors raiding birds' nests for their eggs, as do the Inuit and San people of today. Those eggs are a far cry from what we find at grocery stores, which are mostly produced by factory-farmed laying hens living under abysmal conditions. The healthiest eggs that are widely available come from free-range hens that are fed an organic, natural diet, and not treated with antibiotics. The egg-shells are typically thick and hard, and the yolks a dark yellow.
The medical literature on the health impact of egg consumption has been confusing, partly because the majority of commercially sourced eggs are not the healthiest. A recent analysis of epidemiological studies and clinical trials indicates that the cholesterol in egg yolks does not contribute to high blood cholesterol. In fact, evidence from recent high-quality studies suggests that eggs, when eaten regularly as part of a balanced diet, have a positive or neutral effect on health.
The Lacto-Vegetarian Diet
Dairy products were not a part of our early ancestors' diet. It wasn’t until about 12,000 years ago that humans domesticated herbivores and began consuming their raw and fermented milk. However, most of our ancestors had difficulty digesting it. Malabsorption of the milk-sugar lactose can cause GI problems such as gas, bloating, pain, nausea, and diarrhea, which are symptoms of lactose intolerance.
Today, only about a third of the world’s adults are genetically equipped to digest lactose, while the great majority is considered to have some degree of lactose malabsorption. In America, lactose malabsorption is estimated to affect 36 percent of adults. There are lab tests available to diagnose this condition, and your gut will let you know if you have lactose intolerance.
The relatively recent addition of nutrient-rich, domestic animal milks to the human diet favored the survival of those individuals with a genetic mutation that enabled their small intestine to continue producing lactase, a lactose-digesting enzyme, when they reach adulthood. As a result, this trait has become more common in the human population.
It is unusual for children to have lactose intolerance, but infants who are born prematurely are more likely to have a developmental lactase deficiency. In many cases of lactose intolerance, oral supplementation with lactase can be beneficial. The bacteria that ferment milk to produce yogurt, kefir, and some cheeses do so by breaking down lactose, which may enable some people with the condition to tolerate those dairy products.
Except for individuals with lactose intolerance or milk allergy, fat-free dairy products such as plain, fat-free, organic Greek yogurt can be a very healthy addition to a vegetarian diet. Claims associating dairy products with an increased risk for prostate and breast cancer are unsubstantiated. A recent systematic review of dairy in relation to prostate cancer found that the data was inconclusive. Overall, current evidence suggests that dairy product consumption decreases breast cancer risk.
If anything, it is the fat in dairy products that might be a cause for concern. There is evidence supporting the current recommendation to limit saturated fat intake, especially for those with hypercholesterolemia, but that guidance was challenged in a 2021 review. A 2022 review concluded that “restrictions on dairy food intake do not seem warranted, although there remains a need to further understand the association of different dairy food types with chronic diseases, perhaps particularly for type 2 diabetes.”
Consumer Reports had a recent article sorting through the conflicting information. It concluded that unless milk causes GI distress, there are no health-based reason to avoid it. Keep in mind, however, that dairy products are no longer considered a necessary part of one’s diet, especially for people who routinely eat a wide variety of healthful foods.
Headlines that say, “Heart-Protective Diet in PURE Study Allows Whole-Fat Dairy” aren’t telling the whole story. That's not what the study claims. The findings suggest that an inadequate intake of essential nutrients presents a much bigger risk than the consumption of saturated animal fats in many less affluent parts of the world. Current Western dietary guidance limiting saturated fats may not be warranted for populations in South Asia, China, and Africa, but they certainly make sense for the United States.
The fact remains that animal fats in industrialized nations can accumulate and concentrate fat-soluble chemical residues from agricultural pesticides and herbicides used on the crops that are fed to livestock. Organochlorine pesticides can persist in the soil, make their way into plants, and then into herbivores that feed on them. A Consumer Reports investigation found PFAS “forever chemicals” (PFOS and PFOA) in some organic milk. Growth hormones and antibiotics that are commonly used in large-scale livestock production can also end up in dairy products.
Heavy metals, including lead, mercury, and cadmium, bioaccumulate, especially in aquatic environments. Industrial by-products known as persistent organic pollutants like dioxins, furans, and polychlorinated biphenyls (PCBs) make their way into the food-chain and concentrate in animal fats. Opting for organic, low- and non-fat dairy products can help to reduce the risk of exposure to contaminants, but not eliminate it entirely.
A recent study found that harmful, pro-inflammatory, advanced glycation end-products (AGEs) were more abundant in diets containing animal fats. Comparing a vegan diet with a Mediterranean diet, researchers found that excluding meat reduced AGEs by 41 percent, while dairy products were associated with 14 percent higher amounts of AGEs.
A large, long-term, prospective, population-based cohort study, published in 2025, found a higher intake of butter was associated with increased cancer, cardiovascular disease (CVD), and all-cause mortality, while higher plant-based oils intake was associated with lower mortality. A 2024 study comparing dietary plant and animal fats found high intakes of animal-based fats, including fat from eggs and dairy products, were associated with an elevated risk for both overall and CVD mortality.
The Pesco-Vegetarian Diet
Sustainably caught, wild seafood is an excellent source of high-quality protein and essential omega-3 polyunsaturated fatty acids (n-3 PUFAs). However, to minimize one's intake of mercury and PCBs, it's best to stick with fatty fish that are ranked low in the marine food-chain, such as sardines, herring, and Alaska salmon, as well as most shellfish.
While vegans are unlikely to relinquish their rigidly held beliefs, more liberal vegetarians might be persuaded to take a clue from the healthy and medically recommended Mediterranean diet and its more recent variations, the MIND and DASH diets. These diets, while heavily plant-leaning, also include a fair amount of seafood. They have been shown to reduce the risk for developing cardiovascular disease, type 2 diabetes, certain cancers, and dementia.
If seafood is a non-starter for vegetarians, then for the sake of their brain and heart they might be willing to take a USP-verified fish oil or krill oil supplement containing the omega-3s, DHA and EPA. Recently published results from a three-year randomized clinical trial suggests that older adults with a genetic predisposition to Alzheimer’s disease may benefit from fish oil supplements.
Wholly Animal-based Diets
At the other, hypothetical end of the extreme eating spectrum, we might imagine a “meatarian” diet that totally excludes plant-based foods. Fortunately, there has been no such thing, until now. Thanks to the Internet, social media, and wacko conspiracy theories, there are now “carnivore influencers” claiming that plants are trying to kill us and putting their lives at risk by totally avoiding them.
Humans aren't carnivores biologically, and could never have survived on meat alone. Plant-based dietary fiber is essential for our gut health, and plants contain many phytonutrients that have other, far-reaching benefits for our health and well-being. That said, we probably don’t have to consume as many carbohydrates found in the typical American diet. A new analysis suggests that all our nutritional needs can be met by low-carb diets, but is that really necessary when there are other ways to lose weight?
Although big-game hunting by our lineage began about two million years ago, the biological characteristics of modern humans’ teeth and digestive system suggest that we are not well adapted for devouring chunks of raw meat. On the other hand, insects, which are far more abundant than mammals, may have been a primary source of protein, fat, and other essential nutrients for our distant ancestors. Today, insects are being reconsidered as a food source.
Lots of evidence shows that both Homo neanderthalensis and pre-agriculture Homo sapiens were opportunistic omnivores, eating whatever food they could find as they hunted and gathered. Their diet included lots of items that could be found on a daily basis, such as roots, shoots, and tubers. It is estimated that paleolithic humans consumed as much as 150 grams of fiber per day, while the average American adult eats 10 to 15 grams a day, about half of what is recommended as a minimum requirement for health.
Unlike most mammals, humans cannot make vitamin C, and we must obtain it from plants. Essential minerals, such as potassium and magnesium, are abundant only in fruits and vegetables. Since fiber is only found in plant-based foods, a true paleolithic diet must have included large amounts of plants. For a visceral connection with our forebears I recommend foraging for wild berries or other fruits. We wouldn't be here today if it weren't for our ancestors' omnivorous propensities.
For most “meat-and-potato” Americans, the last thing they want to hear is that red meat and processed meats are bad for their health. Red meat comes from the muscles of mammals, and includes beef, veal, lamb, mutton, goat, and pork. There are now numerous studies linking red meat to cardiovascular disease, some cancers, and diabetes. A recent meta-analysis found a greater adherence to a plant-based diet was associated with a reduced risk for breast, pancreatic, and prostate cancer.
A recent study implicated blood-based (heme) iron in mammalian (red) meat as being responsible for increasing the risk of type 2 diabetes (T2D) by 26 percent. Researchers also identified a number of biomarkers, including L-valine, L-lysine, uric acid, and several lipid metabolites, that may play a role in the link between heme iron intake and TD2 risk. These findings also raised concerns about the addition of heme to plant-based meat alternatives to enhance their meaty flavor and appearance.
Another recent study found strong evidence for a link between frequently eating red meat and processed meats and an increased risk for developing type 2 diabetes. The meta-analysis looked at data from nearly two million adults, representing 31 different cohorts, who were followed for 7–15 years, making this the largest study of this topic. For poultry, associations were significant in the European region, but were less precise in other areas, and thus deserves further investigation. In contrast, a recent meta-analysis of 21 randomized controlled trials found that red meat intake did not affect most of the well-established determinants of glucose tolerance.
A recent study by the Cleveland Clinic found that diet-derived metabolites play a significant role in the risk of early-onset colorectal cancer (CRC). In particular, those metabolites are related to the consumption of red and processed meats. The gut microbiome was also found to play a role, but the data clearly indicated that the main driver of risk at younger ages is diet.
The World Health Organization (WHO) has classified unprocessed red meat as a Group 2A carcinogen, based on limited evidence from epidemiological studies showing a probable association with colorectal cancer. However, this relationship might have more to do with red meats' saturated fats, chemicals from farming practices, and the manner in which it is cooked. The higher the cooking temperature, the worse that meat is for your health.
While on the subject of dietary fats, be aware that some fats increase inflammation, while others tend to be anti-inflammatory. The fats and oils you consume on a daily basis can have a significant effect on your health:
The WHO has classified processed meats as Group 1 carcinogens, which means there's strong evidence that they cause cancer. It would thus be best to think of processed meats, such as bacon, sausages, ham, pepperoni, salami, chorizo, hot dogs, corned beef, pastrami, Spam, jerky, smoked meats, bologna, luncheon meats, deli-sliced meats, and chicken nuggets, as being poisonous, and to avoid them as much as possible.
The Happy, Healthy Omnivorous Diet
A diverse and seasonally varied diet, consisting primarily of whole and minimally processed plant-based foods, along with healthy sources of animal-based nutrients, can be considered optimum for most people. In addition, for the sake of our health, we will need to avoid the tasty but highly processed foods that populate the majority of grocery store shelf space and advertising budgets. Foods that are high in sugars, salt, and saturated fats have a taste appeal, which is why they are consumed in excess, especially when dining out.
The American Heart Association recommends limiting the daily intake of saturated fats that accompany meats and most dairy products. Saturated fats, such as margarine, shortening, butter, and lard, solidify at room temperature. There are also vegetable oils that contain large amounts of saturated fats, such as coconut and palm oils. However, not all saturated fats are created equal, and their metabolic impacts depend upon the chain-length of their fatty acids. The longer the chains, the less healthy the fats seem to be. A person's genetic makeup can also be a factor in determining the health impact of various kinds of fats.
Elderly people who habitually ate a balanced diet consisting of vegetables, fruits, cereal grains, nuts, seeds, legumes, and moderate amounts of dairy, eggs, and fish, were found to have better mental health and superior cognitive abilities compared to other dietary patterns, such as vegetarian, high protein and low fiber, and low starch, according to a recent study.
For an in-depth look at the nutritional principles behind a healthy diet, plus how to make preparing healthy meals really easy, and a hundred recipes to inspire your culinary creativity, check out my recently updated eBook:
“Rx for Healthy Eating” is available from Barnes & Noble, Google Play Books, and the Amazon Kindle Store.
If you’re new to the world of digital libraries, you don't need a special device to read eBooks. Simply download the appropriate app onto your computer, smartphone, or tablet, download the eBook that you want, and you're good to go. It’s brilliant idea to carry your personal library in your pocket.
You can demonstrate your interest in healthy eating, and show your support for my public service as a health educator, by downloading the book, and sending it as a gifts to others who you care about. It costs less than a burger and fries, but unlike the aforementioned fast food, it could save you from a heart attack. Even if you think you know all about healthy eating, I’m sure you’ll learn something new and valuable from my book.
The Sprats' Lesson
Jack Sprat could eat no fat,
His wife could eat no lean,
And so between the two of them,
They licked the platter clean.
There is no one-size-fits-all diet. As the old saying goes, “One man’s meat is another man’s poison.” What nourishes the Inuits might prove harmful for the San. You will need to “listen to your body” and pay attention to how it responds to what you feed it, in order to personalize an eating pattern that is optimum for your own health and happiness.
Remember, too, that you are not just feeding yourself. You are also hosting a very large community of microbes inside your digestive tract, and you will need to properly nourish them if you want them to perform for your benefit. A recent review found that the source of protein and fats in one's diet affects the gut microbiome and its influence upon the development of obesity.
The gut microbiome metabolizes dietary fiber from plants to produce short-chain fatty acids (SCFAs) such as butyrate that increase amounts of GLP-1s, sometimes referred to as “nature's Ozempic.” A review of these SCFAs suggests that they are able to decrease inflammatory cytokines and protect against colon cancer. They also decrease insulin resistance and lower the risk of type 2 diabetes. I will have more to say about the care and feeding of the gut microbiome in a future issue.
Dietary Guidelines
In America, the federal dietary guidelines are influenced by agriculture and food industry lobbying, using industry-sponsored research of dubious validity. USDA scientists have demonstrated that it is possible to claim that a diet is healthy when 91 percent of its calories come from selected ultra-processed foods. There was no mention of the harms caused by UPFs.
The Dietary Guidelines for Americans for 2025-2030 are currently being worked on by a committee consisting of 20 nationally recognized experts in food and nutrition. They will be providing the U.S. government with advice about what Americans should eat and drink to promote healthy growth and development, help prevent diet-related chronic disease, and meet nutritional needs.
At the end of the last five-year project, both the HHS and USDA rejected the experts' recommendations that the guidelines establish lower limits for sugar and alcoholic beverage consumption. The U.S. wine industry is again lobbying against guidelines that might follow the WHO recommendations. Canada’s current dietary guidelines recommend no more than two drinks per week.
In Canada, healthy eating and drinking recommendations are based entirely upon the science. There, a healthy diet is composed of whole or minimally processed foods. Half of one's food intake should consist of fruits and vegetables, a quarter is mostly legumes, seed, and nuts, and the remaining quarter is whole grains. Meat and dairy are considered optional, rather than recommended. Plain water is promoted as the beverage of choice.
It should be noted that the majority of the baby foods sold in the United States fail to meet international nutritional standards. The only specific recommendations created by the FDA are for infant formulas, milk, and oral electrolyte solutions. Baby foods are basically unregulated, and almost all manufacturers make misleading health claims. Of the 651 baby and toddler food products tested, 70 percent didn’t meet protein guidelines, 44 percent exceeded total sugar allowances, and 20 percent exceeded sodium guidelines.
The Planetary Health Diet
A team of European scientists recently developed flexible dietary guidelines capable of nourishing billions of people while minimizing environmental damage and reducing deaths from diabetes, heart disease, and other diet-related illnesses. To that end, they reviewed nearly all the recent medical, nutritional, and environmental research. A sustainable eating plan that is healthy for both people and the planet is presented here.
To that I would add healthy eating recommendations that include checking the ingredients on food labels, and eating your meals slowly and mindfully, without the distraction of television and other kinds of screens. Pay attention to what and how you are eating. Sharing mealtimes with others can enhance your enjoyment of healthy foods and emotional wellbeing. Cook at home much more often, and try out new recipes.
I urge you to ignore food and restaurant advertising. Focus on healthy nutrition, rather than the over-stimulation of your taste receptors and addictive pleasure centers in your brain. You can actually reprogram your thinking to prefer the taste of healthy foods using the Edgy Veggies Toolkit. Learn to love what’s good for you, and unhealthy habits will start fading away.
While you’re up-leveling your eating habits, I suggest that you stop snacking while doing something else. If you’re hungry, and you haven’t yet had your last meal of the day, go ahead and make yourself something healthy to eat. The problem with inattentive snacking is that when you don't focus on the food itself while eating, and haven’t limited the portion size, you are likely to overlook the internal signals of satiety and overeat.
Be Flexible
I remember my time as a medical student when our neuroanatomy class was examining a human brain. It had previously resided inside the skull of a young man who had first become a vegetarian, then a vegan, then a fruitarian, and finally, a breatharian. He claimed his diet was helping him reach a state of spiritual enlightenment, shortly before he died of starvation. Amazingly, his brain was the only part of his body that had not withered away.
I want to caution against any highly restrictive diet, unless it is medically necessary. Rigidly following a self-imposed diet comes with the risk of developing orthorexia, a paradoxically unhealthy obsession with healthy eating. This disorder appears to be more common among dietitians and nutritionists, yoga practitioners, endurance runners, and Instagram users, according to some studies. As with bulimia and anorexia, at its most extreme orthorexia can be fatal.
Let me reassure my readers that I do not have the disorder, and can still eat a fast-food burger every now and then without any guilt. The point is to be both healthy and happy, and not become an obnoxious bore about your diet. For a lot more information about healthy eating, you might want to take a look at some of my books on the subject.
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