Vegan vs Keto vs Ayurveda Diets: The Pros and Cons

Vegan vs Keto vs Ayurveda Diets: The Pros and Cons

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The World of Dieting

In my recent interview with University of Washington Professor Gerald Pollack, an award-winning water scientist, we got to talking about how little the scientific community actually knows about the human body. We both agreed that for those who are searching for the truth, the more you learn, the less you seem to know.

This could not be truer than in the world of diets, where the more you read, the more confused you become. When this happens, I always suggest looking at both science and ancient wisdom to find out more about what we don’t actually know—yet!

The Good News on Vegan and Keto Diets

More than ¾ of food purchased in American households is moderately to severely processed, which has been linked to a number of health concerns, including the soaring rates of obesity.1 Avoiding processed foods alone would likely change the rising rates of chronic illness.

In this article, I attempt to compare the good, the bad, and the ugly of the ketogenic, vegan, Ayurvedic, and longevity diets.

Vegan and Keto Diets

Both of these diets cite good science to back them up, but to the average American, they are both scary, extreme, and hard to follow. While compliance is an obstacle for both the keto and vegan diets, they are also both weak in time-tested ancestral wisdom.

True ketogenic diets suggest consuming up to 70–80% of the diet as fat. The only cultures that came close to this are the Inuit and Siberian people inside the Article Circle, who acquired a gene variant called the Artic Variant, which resists ketogenesis. Basically, when humans were exposed to a 70–80% high-fat diet, they acquired a variant to the gene CPT1A to resist maintaining ketogenesis.

For the Inuits and Siberians, this gene variation is not only linked to resistance to sustained ketogenesis, but also to increased infant mortality, inability to sustain fasting, and increased risk of severe hypoglycemia. This makes me question: why did human evolution resist the long-term state of ketogenesis, even at such a price?2, 3

I am also haunted by science linking a high saturated fat diet to heart and artery disease, fatty liver, and insulin resistance9 (even though I am well aware of the science that disputes this, showing numerous benefits from keto and no long-term side effects).10

I have personally experimented with both a strict vegan and keto diet, and while I lost weight on both, and am quite convinced of the medical utility of both these diets, they are extreme and I was concerned about staying on either diet for an extended period of time.

On the vegan side, proponents often cite the fact that hunter-gatherers were mostly plant-based, which is true, and that they ate very little meat (as low as 15-19% protein) which is also true,4, 5 but they were still hunter-gatherers. They may not have started out as the greatest hunters, but anthropologists agree that there were no vegetarian hunter-gatherers.

Vegan diets have inherent deficiency risks that require supplements of vitamin B12vitamin D3omega-3 fatty acids, and possibly other nutrients.6, 7 I have no problem taking these supplements, but if a diet requires supplements, then clearly our ancestors weren’t eating exactly in this way.

Harvard Health Publishing reviewed the keto diet and had reservations about its long-term effectiveness. They concluded that “a balanced, unprocessed diet, rich in very colorful fruits and vegetables, lean meats, fish, whole grains, nuts, seeds, olive oil, and lots of water seems to have the best evidence for a long, healthier, vibrant life.”22 This diet is neither keto nor vegan!

I am comfortable with having clean saturated fats (like ghee and coconut oils) in my diet as they have been consumed for thousands of years. While on the keto diet, the number of fats I needed to consume to be satiated or maintain ketosis was massive.

Currently, a study is underway comparing a high-carbohydrate low-fat diet to a ketogenic high-fat diet.15 Researchers question if the benefits of the ketogenic diet are solely due to weight loss. The same could be said about a vegan high-carb low-fat diet: that just losing weight, not the specifics of the diet, is responsible for the health benefits.15

As for heart health, the keto diet has shown positive outcomes such as significant reductions in plasma triglycerides, fasting plasma glucose, glycated hemoglobin, plasma insulin, C-reactive protein, systolic and diastolic blood pressures, total body mass, abdominal circumference, as well as significant increases in high-density lipoprotein (HDL) cholesterol, with no significant changes in low-density lipoprotein (LDL) cholesterol.15 All these findings are quite impressive, but not all studies came to the same conclusions.9, 13 There are also concerns regarding the long-term impact of keto on sleep, arterial stiffness, and endocrine thyroid function.13, 15

When searching for health risks associated with a 100% plant-based vegan diet, all you find is study after study citing its benefits, including decreased risk of diabetes, mortality, obesity, cognitive decline, heart disease and more.12, 16-18 Also a vegan diet is the ONLY diet that has been documented to reverse heart disease12 and therefore it may be the most healing diet on the planet. But, is a 100% vegan diet meant for 100% of the time?

Both diets are extreme and very hard to follow and I wondered if my patients would be willing to follow such strict dietary advice. For example, a true vegan diet is a whole food, non-processed, and plant-based: that restricts all oils, dairy, eggs, and processed food, which is most bread, pasta, crackers, almond or alternative milks, veggie meats, and more. Coffee and chocolate, for example, are processed foods and frowned upon.

The keto diet is loaded with nuts, seeds, avocados, sardines, salmon, olive oil, coconut oil, ghee, butter, and MCT oil. Meat is allowed but not too much (I stuck with sardines and salmon). Veggies are in except starchy ones. Fruits are restricted, grains are basically out, and beans are minimized.

I do believe that there is compelling evidence of health and therapeutic benefits from both a vegan and keto diet. Keto may be the best diet on the planet to reverse type 2 diabetes and a strict vegan diet is the only diet on the planet that actually reversed heart disease.15 My question is: are these diets too extreme? Are they the best way-of-life diet for health and longevity?

My Gallbladder Theory

The gall bladder is a sac beneath the liver that stores bile 15–20x more concentrated than the bile made by the liver.14 I have always wondered why we have such a massive reserve of bile. The only logical explanation that I can come up with is that our ancestors ate a lot of fat, say eating the brains and guts of a woolly mammoth. Fat is perishable and all of it had to be eaten right away, while muscle meat could be dried and stored. With such a gall bladder, it seems we evolved to be able to feast on fat.

Anthropologists tell us that such feasts were commonly followed by much longer periods of famine. While we do have the ability to consume massive amounts of fat in a sitting, this was not a daily occurrence. Yes, we have the capacity to digest large amounts of fat, but how much and how often?

Bringing it all Together: Ancient Wisdom, Seasonal Eating & Ayurveda

In a recent podcast, I interviewed the author of the bestselling book The Blue Zones by Dan Buettner. He eloquently describes the diets of the centenarian cultures around the world where folks live healthfully into their hundreds. Not surprisingly, the classic Ayurvedic diet is quite similar to the Blue Zone centenarian diets—both 90-95% plant-based.

Watch the Blue Zone Podcast Here.

Read my article linking the similarities between the Ayurvedic and Centenarian diets here.

Ayurveda calls for a vegetarian, unprocessed, 90–95% plant-based, whole food diet that includes small amounts of cultured dairy (mostly yogurt, ghee, buttermilk, and soft cheeses like paneer). There are no eggs, alcohol, stimulants, or meat, except for medicinal purposes. Rice, beans, fruits, vegetables, nuts, seeds, and whole grains make up the bulk of an Ayurvedic diet—all eaten seasonally.

According to Ayurveda, and now Western science, our diet and the microbes in our guts are designed to change seasonally.19 In nature, we naturally cycle in and out of ketogenesis throughout the year but do not stay ketogenic for an extended period of time.

In the late winter and early spring, when food reserves have run out and before the early spring green harvest, it is a time of famine and fasting. Winter hunting may have been a major source of survival for early humans. A diet of hunted food where the entire animal was consumed could encourage ketogenesis, as fat (organ meat) would be the preferred fuel supply over the protein in the meat. The spring famine, when food was scarce, would also encourage ketosis from calorie restriction. Calorie restriction and fasting are part of our evolutionary resiliency—and today, Nobel Prize-winning science.20

Before agriculture, the domestication of animals, and excessive meat consumption, this diet provided just enough animal protein to deliver the needed amount of B12, D3, and omega-3 fatty acids that a vegan diet lacks.

During the summer months, there would be more gathering than hunting as summer provided an easy-to-harvest plant-based diet with a period of feasting in the late summer and early fall when tubers, nuts, seeds, grains, legumes, fruits, and veggies were abundant. Why go hunting when food was so bountiful? Early humans knew that winter hunting would be needed and to overhunt in the summer would leave them starving come winter and spring.

Perhaps both keto and vegan are a healthy part of the human diet, each in its season.

The Ayurvedic and Centenarian Diets

According to Dan Buettner, the centenarian cultures eat a seasonal 90–95% plant-based diet. Their diets revolve around leafy greens, such as kale, spinach, and collards, along with beets, nuts, seeds, seasonal veggies, fruits, whole grains, mostly olive oil, and a daily serving of beans.

Only ~5–10% of the diet is derived from animal protein, which includes small amounts of meat, dairy (from cow, sheep, and goat), eggs, and fish. They drink large amounts of water, along with some tea, coffee, and wine.

Many centenarians get their 5–10% animal protein mostly from fish, as prescribed by UCLA longevity scientist and author of The Longevity Diet Valter Longo, whose studies suggest fish may be a better source of B12 and omega-3s than dairy, as prescribed in Ayurveda.

Both the centenarian and Ayurvedic diets are 90-95% vegetarian. Ayurveda follows the principle of ahimsa, or non-violence, so they choose to get animal protein from mostly cultured, grass-fed, organic, unprocessed dairy. The 5-10% animal protein from dairy is just enough to deliver the B12, K28 and omega-3 fatty acids that a pure vegan diet would lack.

The heart-healthy vitamin K2, found in dairy, has been shown in many studies to protect the body from cardiovascular disease. Studies show that vitamin K2 has matrix proteins that direct the high amount of calcium in dairy away from the arteries and towards the bones. Vitamin K1 is found in vegetables but does not convert efficiently into K2. It seems nature has something in place like K2 to prevent cardiovascular risk.21

Learn More about Vitamin K2 Max Here.

My Conclusions

There is no doubt about the astonishing health benefits of a 100% plant-based diet. Currently, more longitudinal studies are digging into the long-term benefits of a ketogenic diet, where the science is somewhat controversial.

My conclusion for now is that a primarily plant-based seasonal diet as prescribed by Ayurveda and the centenarians is the long-term healthiest diet. Both the centenarian and Ayurveda diets remain seasonal, hunprocessed, unrefined and 90–95% plant-based.

In a traditional sense, these seasonal diets incur ketogenesis regularly due to periods of famine and spontaneous calorie restriction and fasting. Religious fasting has continued this practice into modern times.

Learn more about seasonal eating and receive our free monthly seasonal eating guide in your inbox with recipes, grocery lists, and more.


  5. Liberman, Daniel. The Story of the Human Body. Pantheon Press. 2013. p224
  12. Guyton; Hall. Textbook of Medical Physiology. 12th Edition. Saunders Press. PA. 2011.

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Dr. John

3 thoughts on “Vegan vs Keto vs Ayurveda Diets: The Pros and Cons”

  1. I’m a longtime fan and follower of Dr. Douillard. But when it comes to meat he seems to be having a hard time getting unstuck from the past. What, exactly makes meat so unhealthy, except for that old, debunked studies on saturated fat haunt him?

  2. You are describing pre-civilization, that is, prior to 10,000 or so years ago, diet. However, it seems to me that the countless generations of a different sort of diet (wild grains, then cultivated grains; other starches, etc.), would cause our bodies to develop a somewhat different digestive system, i.e., we’ve adapted.

    And maybe we can further adapt to a different way of eating from the omnivorous modern diet – not necessarily because we want to, but because we will have to; this has always been the case since the dawn of time. What the new diet will look like, I don’t know.


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