During my review of the existing scientific literature on nutrition, health, and longevity, I’ve been overwhelmingly convinced that a diet that is mostly vegan with small amounts of appropriately raised fish and eggs is best in the long term for a large majority of people (although I will concede that the number of outliers could be quite sizable and is an area that deserves much further study). Despite the fact that the evidence clearly indicates that, in large population studies, those who consume a small amount of fish have better health outcomes than those who are strict vegans, many otherwise educated and rational people still think going fully vegan is the platinum level diet.

I watched the Game Changers documentary on Netflix recently. I found it really interesting and enjoyable. I was curious what James Wilks was going to say about vitamin B 12. For some reason, I expected him to say that you could get it from eating dirt. However, in the less than one minute he spent on the subject, he concluded that vegans (as well as probably most of the rest of the population) should be taking a vitamin B12 supplement.

One of the things that struck me while watching the documentary was the insistence that even fatty fish contained constituents with known detrimental effects. By detrimental effects, I mean that something else associated with the animal proteins caused alterations to physiology that were associated with inflammation. specifically, heme iron. The perspective of both the film producers and the experts they interviewed seem to be leaning in the direction of “just don’t eat this stuff at all ever.”

However, I cannot reconcile population studies that indicate a diet that contains a small amount of fish is better than a pure vegan diet with research that does not include population studies and suggests otherwise. To accept this position in the absence of large population studies validating the concept would be in violation of Dr. Valter Longo’s five pillars of longevity.

Is there anything that can explain this apparent discrepancy? Perhaps the answer lies in the well-known phenomenon of hormesis. 

I’ve been familiar with the concept hormesis for some time. From www.nature.com/articles/1602507:

Hormesis, the biological and toxicological concept that small quantities have opposite effects from large quantities, is reviewed with emphasis on its relevance to nutrition. Hormetic and other dose–response relationships are categorized, depicted, and discussed. Evidence for nutritional hormesis is presented for essential vitamin and mineral nutrients, dietary restriction, alcohol (ethanol), natural dietary and some synthetic pesticides, some herbicides, and acrylamide. Some of the different hormetic mechanisms that have been proposed are reviewed. The credence and relevance of hormesis to nutrition are considered to be established.

Let me propose a possibility. There are some nutrients that are either only available from and/or most easily available from animal tissues. Vitamin B12 is the most well-known of these. However, essential fatty acids like DHA and EPA do not occur in plants nor in any other food that could realistically be consumed in adequate volume to meet what many researchers agree is vital for optimal health. DHA and EPA are produced by algae and are easily available in vegan form. However, you do have to take a supplement because you couldn’t possibly consume enough algae with your salad. So, for the sake of argument here, let’s stipulate that certain animal products are the only viable whole food source.

Again, population studies are clear. A small amount of fish in the diet is better than a purely vegan diet. (This reference that I keep making is to a study of over 70,000 Seventh Day Adventists over a six year period of time. It is detailed in an earlier post here.) Since the amount of fish necessary to consume to get adequate vitamin B12 and essential fatty acids is actually quite small, this means that the toxic constituents that naturally occur in all animal flesh and come along for the ride might not be a matter for any concern.

Studies that show detriment for the consumption of extremely small amounts of animal products consumed per meal seem to operate on the assumption that those animal products are consumed far more frequently than the amount consumed on Mediterranean, blue zone, or centenarian diets. So, when I hear a statement like more than 1 mg of heme iron on average per day causes significantly increases the risk of cardiovascular disorders and diabetes, I am left wondering what that means for somebody who may only be consuming heme iron a couple of times a week even if the serving on any individual day exceeds 1 mg.

[Editor’s note: The Harvard school of public health website, a source to which I often refer, does not seem to share this concern about heme iron. That is telling, because they definitely seem to take every opportunity to reinforce the importance of a plant-based diet. However, in case of heme iron, they indicate that it is more easily absorbed than nonheme iron and that many vegetarians may have difficulty getting adequate iron without a supplement. Of course, they recommend sources of heme iron that are lower in saturated fat, but this does underscore that the Harvard school of public health is not controlled by vegan zealots, as some seem to think.]

This brings me back to the phenomenon of hormesis. First, let’s add another stipulation. In addition to fish containing good things that are more easily absorbed from them than they are from plants, fish also contain “bad things.” These bad things are also present in most other animal foods. However, what if these so-called “bad things” are, in small doses, actually good things? In other words, too small to trigger a negative effect but just enough to activate beneficial hormesis.

From a recent article in the Oxford Nutrition Review:

The MedDiet, one of the more intensely studied dietary patterns together with the Okinawan diet, is rich in foods containing mild (submicromolar) but significant concentrations of hormetins. Thus, it may be argued that the healthful features attributed to the MedDiet could, at least in part, be ascribed to a moderate and chronic activation of stress-response mechanisms due to the long-term consumption of low doses of these hormetins.

A little further into the article, the authors discuss fish. It turns out that none other than the vaunted omega-3 fatty acids appear to function, at least in part, via hormesis. It also appears that some significant degree of the beneficial effects of plant-based foods may be due to the presence of very small amounts of many different hormetins in all plant foods.

All of this leads me to believe that we are clearly dealing with a dose-dependent mechanism that is active across the food spectrum. The reason one can and should eat large amounts of vegetables is because the ratio of good stuff to bad stuff is much higher in vegetables than it is in animal foods. The amount of vegetables that one would need to consume in order to shift the balance from hormesis to pro-inflammatory is probably more than anyone would reasonably consume in most cases. On the other hand, it could be a significant factor with foods that one could more easily overindulge in, amongst which I would include grains, nuts, and fruits. Interestingly, those foods generally comprised a smaller portion of the Mediterranean diet than vegetables and beans. Of course, all animal products combined comprised an even smaller portion.

From an evolutionary perspective, it makes perfect sense that a population that was well adapted to its environment would naturally adopt a balance of foods that resulted in the greatest level of fitness. As Dan Buettner regularly points out in his lectures on the blue zones, the decisions about lifestyle and foods in the cultures he studied were not made by design. They occurred by trial and error over the centuries.

I’ll end with the words of the famous 16th century physician Paracelsus:

[A]ll things are poison and not without poison; only the dose makes a thing not a poison.

Do you want to know what your ideal diet is? I recently developed a tool to help people identify the ideal diet by electronically tracking certain food categories in relation to certain subjective wellness parameters. Check out the SuperOrganism™ Tracker.