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Vegans need to stop exaggerating the health benefits of a plant-based diet

Sketchy claims and pseudoscience will damage the cause of eating plant-based in the long run. It’s okay to admit that there are some things we just don’t know.

Vegans need to stop exaggerating the health benefits of a plant-based diet
[Images: nico_blue/Getty Images, Leonello Calvetti/Science Photo Library/Getty Images Plus]

On the internet, you’ll find extreme dieters of all types, and many of them will swear to you that theirs is the only healthy way for a human to eat. At one end of the spectrum, there’s Jordan Peterson with his carnivore diet, consisting of nothing but beef, salt and water. At the other, “frugivore” diets pushed by YouTubers and their ilk are not just vegan and raw but almost entirely made up of fresh fruit. And then, of course, we have the classic and unapologetically restrictive weight loss programs like the cabbage soup diet, the Master Cleanse (aka the lemonade diet), and the currently trendy Mono Diet, where you eat only one food.

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Advocates for highly restrictive diets like these tend to massively overemphasize the benefits of their approved food while seriously exaggerating the drawbacks of all other foods. But these are only the most extreme examples of a supposed “wellness” culture that makes huge generalizations and routinely manipulates or straight-up ignores scientific evidence. Unfortunately, this approach ends up polluting even those conversations that do have some legitimate basis—for instance, veganism.

There are plenty of health benefits to a plant-based diet, and unlike the above examples, it’s not even necessarily a particularly restrictive diet—even nonvegans and nonvegetarians who eat primarily plant-based can reap the benefits. But the unfortunate truth is that like most things on the internet, a grain of truth gets stretched far beyond the bounds of what science can actually prove.

It’s not hard to imagine why some voices for veganism might exaggerate or even fabricate health-related claims. The animal agriculture industry enacts gruesome violence against animals, as well as many of its laborers and, of course, the health of the planet. So if health is what will compel people to change their diets in a way that’s beneficial for animals and the environment, it’s easy to see why some activists and influencers would push nutritional facts as the most effective avenue to help end the industry.

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But ultimately, misinformation is only going to harm the movement’s credibility. Veganism is a more widespread idea in our society now than ever before—we can’t afford to risk causing folks to dismiss the whole thing as bunk. And all of this misinformation, exaggeration, and cherry-picking is a shame, because it obscures the actual strong evidence of the benefits of eating less meat, eggs, or dairy: lower risk of heart disease, stroke, and several types of cancer, to name just a few.

Regrettably, conversations around veganism tend to be rife with pseudoscience. It’s not hard to find vegan influencers who spout unproven theories as though they were fact, utilize confusing and misguided logic, or say things that are plainly false—like that a vegan diet can change your eye color. Even actual medical doctors have been known to make dramatic and shaky claims, such as that a single meal high in animal fat can “cripple” a person’s arteries, citing one single, decades-old study that featured just 10 subjects and no control group.

You’ll hear people saying that nothing less than a 100% plant-based diet can be considered optimally healthy, when the reality is, we just don’t have the data to back that up. Sure, there are plenty of studies that do support the general idea that plant-based eating is healthy in one way or another, and plenty of them are recent and use reliable methodologies. But even good data can be woefully misinterpreted. Correlation often gets mistaken for causation, and it’s difficult—if not impossible—to isolate very specific inputs and outcomes (like, does cheese cause cancer?) because human biology and lifestyles are complicated.

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Here’s an example: James Beard Award-winning Washington Post columnist Tamar Haspel points to this Bloomberg article, the headline of which boldly claims, “One Avocado a Week Cuts Risk of Heart Disease by 20%.” Which sounds huge! But a closer look reveals that the study only demonstrates an association between avocados and heart disease, not a causal relationship. Do avocados cut the risk of heart disease, or do people who make overall heart-healthy lifestyle choices just eat a lot of avocados? Based on this study alone, we can’t say. Any conclusion is, at best, a loose interpretation of the facts.

And the issues with nutritional science as we know it today go even deeper. For one thing, many of these studies (including the avocado one) rely on self-reported information from study participants. That’s putting a lot of faith in regular people to accurately and honestly measure their own eating habits, which human beings are famously bad at. When the input data is already in question, it’s hard to trust any conclusions drawn from it.

Even putting that aside, observational studies don’t allow scientists to randomize their study subjects. If we’re just noting what real people are actually doing, we can’t separate the elements we want to examine—for instance, meat consumption—from other factors like income, education, gender, smoking and drinking behavior, and what else they eat. As a result, the kind of information we get from these studies is imprecise; and unless the results include very dramatic, statistically significant trends, it’s risky to extrapolate much from them.

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But getting the kind of data we could reliably work with is more or less impossible. To truly control a study, researchers would have to literally control everything eaten by hundreds of participants (or more) over a period of years, in order to eliminate all (or even most) potential confounding factors. Real human lives are just too complicated to regiment the way a true lab study requires.

Furthermore, the biological world is just more complicated than we’d like to think. Different people have different nutritional needs. For people with certain gastrointestinal conditions, eating fully vegan just isn’t feasible. But even barring that, human bodies are unique and one person may not process a particular food in the exact way another person would. With that in mind, one-size-fits-all health advice of any kind should probably be subject to some heavy skepticism. Given all of this, it’s no wonder that doctors, nutritionists, researchers, and other credentialed experts—not to mention third party interpreters of research, like journalists and other media figures—tend to give diverse, often contradictory advice.

Meanwhile, an alarming portion of the population, and even of the scientific community, are apparently indifferent to nutritional science altogether. Fewer than 20% of medical schools in the U.S. have a single required course on nutrition, and the majority of medical schools teach less than 25 hours of nutrition education in the four years it takes to complete an MD program. All this, despite the fact that diet-related disease—much as heart disease and type 2 diabetes—are among the leading causes of death in the U.S. today.

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Our diet-obsessed culture is constantly searching for a magic bullet to fix all the diet-related problems we face. We try complicated, often punishing, and sometimes even dangerous methods to, ostensibly, “get healthy” (often a euphemism for “lose weight”), based on so-called empirical evidence that’s shaky at best. The fact is, nutritional science just isn’t at a point where we can confidently dole out sweeping directives on how people should eat. Sure, there are some points that the medical community has reached some degree of consensus on: The American Heart Association tells us that “eating a lot of meat is not a healthy way to lose weight,” especially for folks who have or are at risk for heart disease. The Centers for Disease Control and Prevention (CDC) says to avoid processed food and sugary drinks in order to lower our risk of heart disease and stroke. And the American Cancer Society tells us to eat a variety of fruits, vegetables, and whole grains.

“Eat your veggies” and “avoid soda” are probably not groundbreaking bits of advice for most people, and they’re certainly not going to sell any flashy new diet books. Anyone who’s spouting granular advice on exactly what and what not to eat is probably operating more on faith than facts. Perhaps a 100% vegan diet is the healthiest way for humans to eat, after all—but we just don’t know for sure. It’s past time vegan influencers and activists embrace that scientific reality. The credibility of veganism, and the future of a more sustainable and compassionate world, depend on it.

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