Mistakes of a Self-Proclaimed Herbivore

A skeptical analysis of claims of a leading voice in the plant-based movement

I was recently recommended a book purporting the plant-based (vegan) diet as the single best diet for humans. I then sat through an interesting talk given by the author himself, during which he flipped through a digital presentation with snippets of studies, highlighted sentences, exciting anecdotes, and bold claims that, according to this man, should be obvious to anyone who pays attention. He mirrored his view of meat consumption to public opinion of smoking. Eighty years ago, he said, doctors endorsed tobacco (his sources being tobacco advertisements), but now, after seven thousand studies, we know better. So how soon will people know better and switch to this impeccable plant-based diet? This man, by the way, is Dr. Michael Greger, who boasts an M.D., a white lab coat seen all over his website, multiple televised appearances, and a best-selling book, How Not to Die, all aimed to promote living solely on a plant-based diet.

Dr. Greger fills his book and website articles with citations galore. The idea is that anyone can read the sources and verify his conclusions. What he doesn’t admit, though, is that most people won’t check his sources; most will, on good faith, assume Dr. Greger’s citations and conclusions are honest and accurate. He takes advantage of this assumption and cherry-picks studies, changes conclusions, and ignores his own data. Even when he sources correctly, Dr. Greger never shows evidence that contradicts his pro-plant opinions. He, nor his peers, exposes his audience to skeptical opinions of his claims. (There may also be cause to believe his claims are grounded in ethics rather than health, since he used to be the public health director of the Humane Society of the United States, an organization morally and ethically similar to PETA, but this is not my focus.[1])

A quick, but important, aside before I continue. Nutritional science is ripe with bias, and bias exists on any side of an argument. I’ve noticed, in nutritional conversations, people tend to vilify certain positions more than others—pro-milk studies are run by the milk industry and pro-GMO studies are funded by Monsanto and similar companies—but, while this can be true, it does not exonerate the opposing opinions as “better” science—anti-milk studies could be run by animal rights groups and anti-GMO studies organized by the Non-GMO Project. And just because an industry helped fund research does not inherently mean the industry influenced the outcome of that research. Likewise, nullifying a study because it was run by the X industry is not a legitimate argument (technically it’s an ad hominem attack that seeks only to discredit the study without offering legitimate opposing evidence). Sometimes bias is obvious, as I’ll show with Dr. Greger’s use of certain data, but sometimes bias is difficult to catch. The important notes here are that any one study usually does not suffice as conclusive evidence on a topic, and we cannot discredit studies based on funding sources without other information.

FISH

Fish, according to general scientific consensus, is incredibly good for you (sources coming), but Dr. Greger and his plant-based supporters will have none of it . . . until they will. The first cherry-picked (and difficult to disprove) evidence concerns omega-3 fatty acids, which we naturally obtain from fish or fish oil supplements (and some plant foods as well, but research suggests there are more benefits from fish than just the fatty acids). Dr. Greger thinks it an unnecessary nutrient, citing a meta-analysis that claims that omega-3 fatty acid supplementation does not correlate with a decreased risk of various cardiovascular diseases (mentioned around page twenty in his book).[2] By itself, this seems all right, especially since a meta-review is usually a safe study to approach first. But this meta-review turns out to be one of the more heavily criticized publications covering omega-3 fatty acid research. For one, the meta-review includes studies that used only half the recommended daily dose of omega-3 fatty acids, which is clinically insignificant and thus may not demonstrate the fatty acids’ beneficial effects.[3] The review also uses an unusually strict p-value to measure the cutoff for statistical significance (p < 0.0063 instead of the standard p < 0.05 or p < 0.01).[9] And another reviewer points out the study should be “interpreted with caution” due to various other “methodological shortcomings.”[4] Other research suggests benefits of omega-3 fatty acids cannot be truthfully measured when patients are also taking statin drugs (cholesterol-lowering drugs that possibly mask the effects of omega-3 fatty acids), and between 81 and 85% of the participants in the questionable omega-3 fatty acids trials were on statin drugs (as well as beta-blockers, aspirin, and clopidogrel).[5][6] If statin drugs negate the effects of omega-3 fatty acids, the conclusions of the meta-analysis ignore serious confounding factors. By the way, the authors of that last paper suggest that “physicians [should] continue to recognize the benefits of omega-3 PUFAs [poly-unsaturated fatty acids] to reduce cardiovascular risk in their high risk patients.”[10] This is the opposite of what Dr. Greger concluded.

Dr. Greger cites a study that suggests a diet of starchy foods, whole grains, and vegetables leads to lower rates of asthma and wheezing than other diets.[7][8] But he omits that this same study, which he cites on page thirty-nine in his book, concludes that seafood and fresh or frozen fish also correlates negatively with severe wheeze, atopic eczema, and allergic rhinoconjunctivitis.[11] Eating fish is beneficial for those with severe wheeze, but because that disagrees with the all-natural plant-based ideology, you will not hear a word of this from hardcore plant-based supporters. And Dr. Greger can’t say this study is biased by the fish industry, because, well, he cites the study for his own claims. Not surprisingly, numerous studies have shown that oily fish is protective against asthma.[9][10][11][12][13][14]

Most of us aren’t too worried about asthma, though, so what about something more serious, like dementia? Dr. Greger purports that a plant-based diet defies the onset of dementia better than other diets, and he cites a rather old study that suggests African immigrants in America suffer higher rates of dementia than Africans still living in Africa.[15] But again if you read the study’s summary findings, you’ll see that “fish consumption is found to reduce the prevalence of Alzheimer’s disease in the European and North American countries.” Including fish in your diet may reduce your risk of developing dementia, and, balancing for other variables, fish outperforms cereal grains when combating dementia.[16]

So fish is good, right? If you check Dr. Greger’s website, you’ll find a short fearmongering article of why fish will kill you and your babies. This is largely thanks to mercury. But apparently mercury has also been shown to have protective effects (with no noticeable negative effects) on weights of newborns.[17] Another comprehensive study on mercury’s effects on children from birth through the first few years of their lives found “no overall adverse effect upon child development with higher maternal fish intake,” and that “maternal fish intake more than twice a week was associated with improved performance on tests of language and visual motor skills.”[18] The discussion section of that study is well worth a read, but no matter how you look at it, just because mercury exists in fish does not make fish dangerous to consume. It is very easy to say fish is bad because mercury is bad, and the anti-fish perspective uses this to attack the negatives without paying attention to the positives.[19] (This citation says nothing about the anti-fish perspective. It says that fish guidelines focus too much on mercury and too little on the positive benefits of fish, which still supports my argument, but not quite the way you expected.)

Ignoring most data on the benefits of fish is not science, it’s ignorance. I can only say that, despite some good science Dr. Greger purports and the legitimate claims he has for healthier eating, his omission and refusal to accept scientific data on fish is confirmation bias, which should be noted seriously. Feel free to listen to his and his colleagues’ claims, but remember they cut out most of the information. But wait, just because fish is good doesn’t mean plants are better. The prior studies already show that including fish in your diet can be better than a strict plant-based diet. You may also find occasional claims that higher fish consumption leads to certain medical anomalies. It may be possible, but it may be confounded by other variables either ignored or simply not noticed.

MEAT

Meat, in heavy quantities, is not that good for you. High rates of meat consumption correlate with (not cause) various health issues, specifically if meat is processed. But this does not mean you must cut out all meat.

We’ll begin with kidney stones, though I’ll first make a detour to high-oxalate vegetables. Around page one hundred seventy in his book, Dr. Greger cites a study to support his claim that high-oxalate vegetables are not linked to increased kidney stone production.[20] What’s unfortunate here is that this study does not make any such claim. While the study mentions high-oxalate vegetables, it does not say high-oxalate vegetable are uncorrelated with kidney stone creation. The study actually mentions high-oxalate foods as an interference in the research—they “offset the protective association” of vegetables. Another conclusion that contradicts Dr. Greger.

After questionably saving his high-oxalate vegetables he goes on to attack meat as a kidney stone creator. He cites a study to claim that subjects who eat no meat have significantly lower risk of forming kidney stones than subjects who eat high-meat diets (page one hundred seventy).[21] This time the study agrees with his stance. A vegetarian diet significantly reduces the hazard ratio for forming kidney stones when compared with a high-meat diet. But the study doesn’t end there: a low-meat diet (less than 50 grams per day) has a lower hazard ratio (0.52) than a vegetarian diet (0.69) for forming kidney stones. Dr. Greger does not lie, but he omits data that contradicts his claim. According to the real study, which this major plant-based supporter cites, a low-meat diet, even when testing a vegetarian diet, correlates with the lowest risk of forming kidney stones.

While the mood for exoneration is still relatively fresh, let me exonerate meat just a little in regards to dementia. Dr. Gregor, around page fifty-four, cites a study of Seventh-Day Adventists (vegetarians, whom I will address again later) and uses it to claim that vegetarianism prevents dementia.[22] He concludes that people who eat vegetarian diets have a significantly lower risk of developing dementia than those who eat any meat. But the study itself, which has not been replicated, supports this claim only so far as a matched (for age, sex, and zip code) analysis containing 272 participants. The second unmatched portion of the study, containing a sample of 2,984 participants, found “no significant difference in the incidence of dementia in the vegetarian versus meat-eating [participants].” They found no obvious explanation for the matched vs. unmatched difference, but nonetheless found no positive correlation between non-vegetarian diets and dementia onset. Dr. Greger’s citation was not the only study concerning Seventh-Day Adventists, and another similar study also found no statistically significant correlation between meat consumption and dementia.[23] This last study also suggests that certain factors that have been claimed to be linked to an increased risk of dementia (including meat consumption) require “further confirmation as etiologic agents.” While they found no correlation, evidence either way is not strong or consistent enough to draw lasting conclusions. (As another reminder, this is all correlational—even if they did show correlation, we cannot say meat consumption causes dementia). A British study also found higher rates of death from mental disorders among vegetarians than non-vegetarians (albeit with a small sample size).[24] The same study, with a less dubious sample size, suggests that death rates are similar between the two groups, implying that perhaps there are other factors contributing to average death rates than the omission of meat and fish—a vegetarian diet won’t necessarily increase life expectancy.

Dr. Greger makes another claim that requires careful skeptical inspection. To bolster the belief that a plant-based diet is best, Dr. Greger looks at apolipoprotein E4 (apoE4), a supposed major risk factor for Alzheimer’s. In the West, being an apoE4 carrier increases chances of developing Alzheimer’s, but in Nigeria, high apoE4 does not correlate well with contracting Alzheimer’s.[25] Dr. Greger’s explanation? Nigerians stick to a mostly plant-based diet that protects the brain from contracting Alzheimer’s. But this does not paint the entire picture. ApoE4 has been found highest among hunter-gatherers and indigenous groups.[26][27] And, among these groups, apoE4 helps conserve lipids during food scarcity, ease the burden of cyclical famines, and boost survival.[­27] In sub-Saharan Africa, hunter-gatherer groups also show high rates of apoE4, yet Alzheimer’s is still incredibly low.[28][29] Perhaps apoE4 as an Alzheimer’s curse is not so much dependent on plant-based diets, but correlates more with the hunter-gatherer lifestyle of feast-famine cycles, high physical activity, and unprocessed foods not necessarily limited to plants. (Dr. Greger’s Nigerians also eat meat.) These are confounding factors Dr. Greger does not mention as possible explanations for high apoE4 and low Alzheimer’s (plus all sorts of other possible genetic developmental differences). For another possible confounding factor, it’s worth checking average life-expectancy of the compared groups and average age of Alzheimer’s onset. The average lifespan in Nigeria is about 53 years, compared to about 79 years in the USA.[30] According to the Mayo Clinic, about 95% of people develop Alzheimer’s symptoms after age 65.[31] Maybe Nigerians do not last long enough to exhibit Alzheimer’s symptoms, while we do. This is speculation, though worth considering as another confounding factor. And when we involve death or other easily-measurable data, it may be worth checking if a confounding variable (early death, feast-famine cycles, correlated body adaptation) is to blame rather than whatever the study or person wishes to blame. Dr. Greger does not seek to reject his hypotheses, but rather to prove (a naughty word that implies far greater scientific certainty than exists in this field) his own assumptions—and if he fails to prove these assumptions, you will never see the results.

(A quick non sequitur point I wish not to omit. I’ve heard say from the usual suspects that a plant-based diet leads to higher levels of testosterone and, obviously, manlier men. This is an impressive claim to make when most studies demonstrate the opposite: a non-meat diet negatively correlates with testosterone levels.[32][33][34])

Another review study shows no unique health benefits of a vegetarian diet over low-meat diets.[35] In fact, it shows that both vegetarian diets and diets that allow small amounts of red meat are associated with lower risk of diseases (including coronary heart disease and type II diabetes). To maximize health improvements, the study suggests eating a plant-based diet that allows a small intake of red meat, fish, and dairy. This seems to be, outside of the plant-based clique, the standard scientific suggestion. While plant-based diets may not have adverse effects on most people’s health, the restrictive diet results in nutrient deficiencies that can have serious negative health effects on certain types of people, especially pregnant women. The German Nutrition Society published a position paper inspecting the vegan diet based on current scientific literature. Their conclusions are not just cautionary, but rather worrisome: a plant-based diet is not recommended for pregnant and lactating women, infants, children, and adolescents on the basis that it is “difficult or impossible to attain an adequate supply of some nutrients,” the most important of which being vitamin B12.[36] They instead recommend a diet based primarily on plants with small amounts of unprocessed meat and fish for optimal micronutrient intake.

Meat is not evil, as Dr. Greger et al. claim, but it is not saintly. He does point out, accurately, that meat carries human-transmissible viruses. It’s not common (so uncommon it floods national news when it happens, which biases people to think it is common), but E. coli, Yersinia, hepatitis E, and other pesky substances can appear in meat. It’s not anything you or I want to be exposed to, and good cleaning practices and strict regulations do keep the bacteria at bay. Quite recently an E. coli outbreak occurred in, of all things, romaine lettuce. Plant-based supporters will be quick to point out, though, that animals are the spawn of these vile bacteria, not plants, as if to say that us not eating animals will stop these bacteria from existing. It seems quite idealistic that their implied solution is to convince everyone to not eat meat rather than to encourage stricter controls, checks, cleanliness, and regulations to minimize the spread or occurrence of these bacteria.

One last note, and I promise I’ll move away from meat. I’ve heard used the argument, by the anti-meat crowd, that we’re not really omnivores because we have to cook meat, unlike any other true omnivorous animal. It’s an argument based on false assumptions and logical fallacies. Nonetheless, and perhaps for that very reason, I need to address it. Yes, we cook meat. We also cook our plants. Believe it or not, cooking is a biological and adapted human trait.[37] Cooking does not make us false omnivores—humans have been cooking long before we were humans, with some suggesting as far back as over one million years.[38] Cooking meat is not unnatural or somehow cheating—we’ve controlled fire long enough for cooking to affect our evolution (weaker jaws and smaller teeth)—and while other animals do all right eating raw meat, they—even scavengers—still prefer fresh meat over rotting meat.[39] Plus, wild mammals have significantly shorter life spans than their domesticated equivalents.[40] (A feral cat might live only a couple years compared to the same domesticated cat living a healthy ten to fifteen years.) Apart from predators, food scarcity, and other factors, bacteria exist in the wild. Feral animals, while able to handle bacteria we cannot handle, still fall victim to many similar bacteria that hurt and kill humans. We’re humans—Homo sapiens—not vultures, coyotes, wolves, lions. We’ve evolved to cook and eat meat long before we were humans (Homo erectus had physical attributes linked to cooking), and even if cooking is specific to human evolution, so what? It’s no less natural for me to eat a rare steak with farmed asparagus than it is for me to ponder the ultimate purpose of the universe and my existence—another, as far as we know, purely human trait.

MILK

Milk is not evil. Milk is not bad. Milk simply is, and sometimes it is all right. We’ll start again with asthma, which Dr. Greger thinks can also be linked to milk consumption, and again he makes a rather funny mistake, considering it implies he yet again succumbs to confirmation bias. According to him, the study shows that increased milk consumption has been associated with increased asthma risk.[41] But the actual study contradicts Dr. Greger’s claims, saying “daily/weekly consumption of milk/milk products, green leafy vegetables and fruits were associated with a lower asthma risk.” It also found that respondents who never consumed milk or milk products were more likely to report asthma than those who consumed milk or milk products daily. Let me point out again that Dr. Greger used this single same source to say that milk is associated with higher risk of asthma. I wonder where he got that idea. . . . (Two important notes: one, his treatment of data is manipulative, unethical, and unscientific; two, no matter the conclusion, this study, as most of the ones mentioned, shows correlative evidence. He cannot conclude that milk causes higher asthma risk, and I cannot conclude that milk causes lower asthma risk. Correlation, to stab the dead pig, is not causation.)

Asthma is not the only problem. A 2016 review paper suggests that dairy, excluding butter, may be protective of heart disease, or at the very least evidence suggests dairy products do not increase the risk of cardiovascular disease.[42] This is interesting since dairy products are high in saturated fat, but even the saturated vs. unsaturated fat debate has not found a peaceful conclusion.[43] We also have evidence that dairy products are linked with lower blood pressure, but some of the research is funded by dairy commissions and research groups (for the paranoid, this means the dairy industry). Such potentially conflicting biases usually appear toward the end of a research paper—good transparency—and again do not necessarily make the research biased.[44] Folks need money to run experiments and trials, and corporations that have interest in the results may provide funding. It is difficult, without continued studies, replicated trials, review studies, and general skepticism, to determine whether a study is biased or not.

Dairy is a uniquely human food—no other animal cultivates and consumes the milk of another species, and prior to animal domestication it was likely a rare treat, though we do not have evidence on how coveted milk was in pre-history. We can, though, say that humans received the calcium they most likely needed from other dietary sources. While this means milk is not necessary in every diet, it is also not necessarily bad. One of the leading arguments against milk (aside from lactose intolerance) is that suspicion surrounds increased milk consumption with increased rate of osteoporosis (weak or porous bones). Before I look into the evidence surrounding this, it’s important to mention and remember that non-dietary factors, such as exercise and hormones, can also cause osteoporosis (confounding factors).[45][46] Bones store calcium, your body uses and expels calcium, and if you don’t get enough from your diet, your bones become brittle and weak. While we’re here, let’s quickly dispel another myth: high protein diet causes osteoporosis. There isn’t enough scientific evidence to support this claim, and studies generally show the opposite: more protein leads to improved bone health.[47][48][49][50] (Few studies inspect strictly the elderly (over 65). One study, run in 2015, which researched protein intake in only this age group, suggests that animal proteins—including proteins obtained from dairy products—provide essential amino acids lacking in plant protein sources that stimulate muscle protein synthesis and maintain better skeletal muscles in old age.[51]) What about dairy, considering it is rich not only in calcium and protein, but also phosphorus and, sometimes, vitamin K2?[52][53] While a few studies suggest milk intake either has no effect or is harmful, most studies show a positive correlation between high dairy intake and a reduced risk of osteoporosis.[54][55][56][57][58] Neither argument can demonstrate causative behaviors between dairy consumption and osteoporosis, but we do have some causative evidence available—for that we need randomized controlled trials, of which there are few in the nutrition world, but fortunately we have a few on this very issue, and they show that dairy intake is linked to positive effects on bone health, bone growth, decreased rate of bone loss, and improved bone density.[59][60][61][62][63][64][65][66][67] And before you say it, no, those studies were not all funded by the omniscient milk industry. Apart from bone health being significantly more complex than we make it out to be, and nutrition being much more indecisive than most of us are aware, calcium-rich foods are important, and dairy is one of the best sources you will find. Sure, it has sugar and fat, but it’s not going to destroy your bones. Milk may not be as good as the milk industry purports, but I have yet to see good replicated evidence that milk is bad for you.

And how much milk should you have? We have no universal suggestions on the recommended dairy intake, but a review study claims there is no conclusive evidence that we need to modify our high level of milk consumption.[68]

DEFICIENCIES

Supporters hail the plant-based diet as the best diet to keep you healthier and happier and so on. But one thing bugs me. If it’s so good, so perfect, so ideal, why does a strict plant-based diet result in various lacking deficiencies, including vitamin B12, vitamin D (the recommended D3 is usually an animal-derived product; vitamin D2, which comes from plants, is significantly less potent than D3), carnosine (linked to reduced muscle fatigue), omega-3 fatty acids, heme-iron, and iodine.[69] Why would the perfect diet, the diet we obviously all need to adopt, result in serious lacking nutritional deficiencies? This, to me, does not sound like the perfect diet at all, but rather a restrictive diet that does not provide humans with enough nutrients. Even if we are not designed for the massive meat consumption common in our society, we are designed to take and process a variety of foods, including meat, fish, and dairy. Not only are we designed to process such foods, we need their nutrients, as the studies I (and Dr. Greger) have cited demonstrate. It seems that the recommended diet is not a strict plant-based diet, but a plant-based diet with some fish, unprocessed meat, and dairy (unless you want to treat food selection like a science project to ensure you receive enough of the right nutrients). This diet provides the nutrients you need, a wealth and variety of flavors and dishes, and health benefits purposefully ignored in plant-based advocacy.

If these deficiencies concern you, and you have read Dr. Greger’s book, you might not have learned about the dangers of such deficiencies. Why? Probably because it’s a pretty serious argument against such a diet, and because Dr. Greger does not mention vitamin B12 until the end of the book. Not the last chapter; you’ll have to flip past the conclusion, the acknowledgments, and head to the supplement pages, which, just like his numerous cited studies, probably lack the close reading they require. Vitamin B12 deficiency is serious. It can lead to pale or jaundiced skin, problems producing red blood cells, megaloblastic anemia, weakness, fatigue, nerve damage, nervous system damage, problems with balance and coordination, mouth ulcers, glossitis, breathlessness, dizziness, optic neuropathy, high temperatures, and mood and brain disorders including depression and dementia.[70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92] Of course the easiest way to obtain enough vitamin B12 is to eat a little meat. Same goes for iodine (also not mentioned until the end of his book), which helps thyroid and hormone regulation and is considered important for pregnant and breastfeeding women.[93] The main sources of iodine are seafood, eggs, and dairy.[94]

I won’t say supplements are cheating. In the northern hemisphere most of us should take vitamin D3 pills because woe be us when the sun vanishes during winter. But you cannot pass off a diet as the single healthiest diet if it relies on extraneous supplementation made possible only by modern chemical advances. Our bodies also do not absorb supplements as readily as naturally-bound nutrients, and evidence suggests the capacity of our intrinsic factor limits the body’s ability to absorb supplemental vitamin B12 (about 56% absorption from a 1 mcg dose and less as the dose increases).[95]

A plant-based diet lacking sufficient supplementation is prone to as many debilitating medical issues as a high-meat diet. A plant-based diet is prone to serious issues in pregnant women and children’s cognitive development and is not (see fish section) recommended for pregnant women or children or adolescents. Why, then, is it so good? Is it because a couple studies that show moving a person from an absurdly high-meat diet to a plant-based diet resolves serious medical conditions, including cardiovascular health, diabetes, or heart issues? Or is it that they never bothered checking if a low-meat diet has the same or better effects? (Or are these studies correlational with no leeway for causative conclusions?) The studies I cited that do include low-meat diets or, alternatively, fish diets (meaning a mostly plant-based diet with a little fish or meat) tend to show that a plant-based diet with a little meat and fish is consistently the healthiest.

HEALTH

What does health mean? Do people switch to “healthy” diets because they were told those diets will lead to improved longevity and less heart disease or improved mental health and social inclusion? There are numerous physical definitions to good health, many of which plant-based advocacy address, but they seem to omit the psychological aspects of health. For one, children who choose a diet not accepted by their families might see social isolation when their parents refuse to cook meals according to those children’s diets. Ditto for social gatherings or cookouts where extra effort has to be made to serve the one person who eats differently. Cognitive effects of our diet may not be as apparent as physiological effects, but they must still be considered. So what is health? We assume it is whatever the current medical community considers the cause of longevity. But who mandates that longevity is healthiest? I, for one, would much rather live a happy and successful sixty years than a miserable ninety years. Health is not one standard dependent variable, as some suggest. Health is built from assumptions, perspectives, physiological longevity, psychology longevity, comfort, success, happiness, political safety, economic pleasure, and so on.

But if you’re certain only longevity matters, you must wonder whether we have adequate evidence to suggest a restrictive vegetarian or vegan lifestyle is worth it. There’s too little evidence to say so conclusively, but most of it suggests there is no significant difference—genetics will kill you sooner or later. We do, though, have limited data from one group, the Seventh-Day Adventists (SDAs). SDAs live a strict non-smoking, non-alcoholic, non-drug, vegetarian lifestyle (among other restrictive behaviors). One study suggests that, on average, SDA men live about 7.3 years longer and SDA women about 4.4 years longer than other Californians (only Californians in this study).[96] So the conclusion of any bad scientist is that a vegetarian diet leads to a healthier, longer life. But this is a correlational study based on observational data, and—and this point is, for many, hard to understand—it is only a correlational study. So why did they live longer? Maybe the lack of alcohol, smoking, or one of their other rigorous behaviors caused their longer average lives. Maybe their affluence helped. If most SDAs are middle to upper class, you can’t compare such a socio-economic lifestyle to the rest of California, which includes the wealthiest people and the poorest. Perhaps they lived longer because their entire community endorses vegetarianism, and thus there are no cases of social isolation due to diet and fewer instances of cognitive disorders. Maybe, if we accommodated all these confounding factors, SDA life expectancy wouldn’t be that much longer than the average person’s. This raises an important question: how much longer do you need to live in order to limit your lifestyle to a restrictive diet? To me, the unguaranteed chance of four extra years is not worth it. Genetics will catch most of us first, and by that time we won’t know whether we lived longer because of one habit or a hundred other factors.

So when plant-based advocates say their diet is healthier, ask them by what standard. Is a reduced risk of heart disease going to make or break switching to their diet? Maybe people who voluntarily switch are already more conscious of their health or more capable to deliberate on and change their diets, and thus are healthier due to other reasons than those who are not concerned with their diet. Maybe they convince themselves they will be healthier due to their diet and mentally influence their own health (e.g. they begin exercising more because they see that as a byproduct of being healthier). We have a splattering of mostly correlational and often fallacious research that suggests a splattering of conclusions, but none of this is enough to indicate one habit reigning supreme over others. There is more to life than heart disease (and osteoporosis and dementia and depression and social anxiety and comfort and taste and personal happiness), but you will never hear this from the plant-based advocates.

FINAL THOUGHTS

I hope, in writing this, that I do not succumb to the same biases as those I argued against. But I am biased, and I certainly missed data that disagrees with me. I am also no expert in this field, and I may be unable to explain why one study disagrees with my conclusions while another agrees with me—this does not make my arguments wrong; disagreement is good for science, and science isn’t some pop-news website where the loudest voice wins. If you agree with my points, read Dr. Greger’s opinions and research the topic and form your own opinions. No matter the claim, the strongest and simplest skeptical approach you can make is to look for possible confounding explanations. Dr. Greger says he does the research so you don’t have to. But given his biased position and his never sharing data or research that conflicts with his interests, you cannot trust him. When he says his beliefs are best, and when he ignores conflicting opinions (based on his flawed conclusions), he breeds not scientific thinking, but religious obedience. If I disagree with his arguments, it’s not because I have data and evidence, it’s because, according to Dr. Greger, I’m simply not enlightened enough. Dr. Greger relies on religious acceptance, not science. He is a pastor and a salesman, not a scientist, and while a pastor can speak the truth, a pastor should not act or be treated as a scientist.

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[2] association between omega-3 fatty acid supplementation and risk of major cardiovascular disease events: a systematic review and meta-analysis
[3] omega-3 fatty acid supplementation and cardiovascular disease events
[4] omega-3 fatty acid supplementation and cardiovascular disease events [reply]
[5] omega-3 fatty acid supplementation and cardiovascular disease events—reply
[6] do omega-3 polyunsaturated fatty acids prevent cardiovascular disease? a review of the randomized clinical trials
[7] some grains contain gluten, which causes problems for many people
[8] diet and asthma, allergic rhinoconjunctivitis and atopic eczema symptom prevalence: an ecological analysis of the isaac data
[9] consumption of oily fish and childhood asthma risk
[10] dietary supplementation with fish oil rich in omega-3 polyunsaturated fatty acids in children with bronchial asthma
[11] protective effect of fish oil supplementation on exercise-induced bronchoconstriction in asthma
[12] asthma and allergic rhinitis at 4 years of age in relation to fish consumption in infancy
[13] relationship of fish and cod oil intake with adult asthma
[14] fat and fish intake and asthma in japanese women: baseline data from the osaka maternal and child health study
[15] dietary links to alzheimer’s disease
[16] 11 evidence-based health benefits of eating fish
[17] blood mercury levels and fish consumption in pregnancy: risks and benefits for birth outcomes in a prospective observational birth cohort
[18] maternal fish intake during pregnancy, blood mercury, and child cognition at age 3 years in a us cohort
[19] a review of guidance on fish consumption in pregnancy: is it fit for purpose?
[20] dietary intake of fiber, fruit, and vegetables decrease the risk of incident kidney stones in women: a whi report
[21] diet and risk of kidney stones in the oxford cohort of the european prospective investigation into cancer and nutrition
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[23] variables associated with cognitive function in elderly california seventh-day adventists
[24] mortality in british vegetarians
[25] roles of apolipoprotein e in alzheimer’s disease and other neurological disorders
[26] apolipoprotein e allele distribution in the world. is apoe*4 a ‘thrifty’ allele?
[27] lipoprotein profile of a greenland inuit population. influence of anthropometric variables, apo e and a4 polymorphism, and lifestyle
[28] high frequency of the apolipoprotein e *4 allele in african pygmies and most of the african populations in sub-saharan africa
[29] high frequency of the apo e4 allele in khoi san from south africa
[30] world health rankings: nigeria life expectancy
[31] early-onset alzheimer’s: when symptoms begin before age 65
[32] serum sex hormones and endurance performance after a lacto-ovo vegetarian and a mixed diet
[33] dietary and hormonal interrelationships among vegetarian seventh-day adventists and nonvegetarian men
[34] effect of a vegetarian diet and dexamethasone on plasma prolactin, testosterone and dehydroepiandrosterone in men and women
[35] vegetarian diets, low-meat diets and health: a review
[36] vegan diet: position of the german nutrition society
[37] ‘cooking as a biological trait’
[38] every human culture includes cooking – this is how it began
[39] scavenging efficiency of turkey vultures in tropical forest
[40] most mammals live longer in zoos than in the wild
[41] prevalence and risk factors for self-reported asthma in an adult indian population: a cross-sectional survey
[42] new perspectives on dairy and cardiovascular health
[43] why is harvard ticking the knife into butter again?
[44] impact of dairy consumption on essential hypertension: a clinical study
[45] exercise for preventing and treating osteoporosis in postmenopausal women
[46] hormonal influences on osteoporosis
[47] dietary protein and skeletal health: a review of recent human research
[48] dietary protein: an essential nutrient for bone health
[49] prospective study of dietary protein intake and risk of hip fracture in postmenopausal women
[50] dietary protein and bone health: a systematic review and meta-analysis from the national osteoporosis foundation
[51] association of protein intake with the change of lean mass among elderly women: the ostpre-fps
[52] phosphorus nutrition and the treatment of osteoporosis
[53] vitamin k and the prevention of fractures: systematic review and meta-analysis of randomized controlled trials
[54] milk, dietary calcium, and bone fractures in women: a 12-year prospective study
[55] case-control study of risk factors for hip fractures in the elderly
[56] effect of diet and lifestyle on bone mass in asian young women
[57] anthropometric, lifestyle and menstrual factors influencing size-adjusted bone mineral content in a multiethnic population of premenopausal women
[58] postmenopausal bone density and milk consumption in childhood and adolescence
[59] effects of dairy products on bone and body composition in pubertal girls
[60] calcium-enriched foods and bone mass growth in prepubertal girls: a randomized, double-blind, placebo-controlled trial
[61] effect of calcium supplementation on bone mineral accretion in gambian children accustomed to a low-calcium diet
[62] dietary modification with dairy products for preventing vertebral bone loss in premenopausal women: a three-year prospective study
[63] the effects of calcium supplementation (milk powder or tablets) and exercise on bone density in postmenopausal women
[64] evidence for an interaction between calcium intake and physical activity on changes in bone mineral density
[65] calcium supplementation prevents seasonal bone loss and changes in biochemical markers of bone turnover in elderly new england women: a randomized placebo-controlled trial
[66] long-term effects of calcium supplementation on serum parathyroid hormone level, bone turnover, and bone loss in elderly women
[67] low dose estrogen and calcium have an additive effect on bone resorption in older women
[68] osteoporosis: is milk a kindness or a curse?
[69] evidence that vitamin d3 increases serum 25-hydroxyvitamin d more efficiently than does vitamin d2
[70] biologically active vitamin b12 compounds in foods for preventing deficiency among vegetarians and elderly subjects
[71] megaloblastic anemias: nutritional and other causes
[72] megaloblastic anemia and other causes of macrocytosis
[73] clinical approach to jaundice
[74] pronounced pancytopenia with concomitant jaundice in a 66-year-old woman
[75] diagnosis and classification of pernicious anemia
[76] cobalamin deficiency: clinical picture and radiological findings
[77] neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis
[78] vitamin b12 and folate deficiency in later life
[79] low micronutrient levels as a predictor of incident disability in older women
[80] vitamin b12 in health and disease
[81] vitamin b12 deficiency presenting as acute ataxia
[82] glossitis with linear lesions: an early sign of vitamin b12 deficiency
[83] clinical manifestations of the mouth revealing vitamin b12 deficiency before the onset of anemia
[84] glossitis with linear lesions: an early sign of vitamin b12 deficiency
[85] atrophic glossitis from vitamin b12 deficiency: a case misdiagnosed as burning mouth disorder
[86] b12 deficiency with neurological manifestations in the absence of anaemia
[87] optic neuropathy in vitamin b12 deficiency
[88] you are what you eat: ophthalmological manifestations of severe b12 deficiency
[89] systematic review and meta-analysis of randomized placebo-controlled trials of folate and vitamin b12 for depression
[90] vitamin b12 for cognition
[91] pseudodementia in a twenty-one-year-old with bipolar disorder and vitamin b12 and folate deficiency
[92] pyrexia in a patient with megaloblastic anemia: a case report and literature review
[93] iodine supplementation in pregnant and lactating women
[94] iodine deficiency
[95] nih fact sheet: vitamin b12
[96] the adventist health study-1: gathering data