June 2019
IS VEGAN REALLY THE HEALTHIEST DIET?
Some of the things you read about this plant-based diet would have you believe that the omnivores among us are doomed to extinction (or at least disease). We separate the solid science from the hype.
One of the most important forces reshaping the American diet is the quest for a magic bullet: a simple, all-powerful something that we can eat (or avoid) to find ourselves instantly slim, healthy, beautiful and wise. Kale, acai, water, gluten-free anything, we’re ready to believe. Lately, veganism, or avoiding all animal products, including eggs, dairy and honey, is the bullet of choice among the glamorous. But some advocates are spouting “facts” about veganism and health: They declare the World Health Organization (WHO) said eating meat is as carcinogenic as smoking. (It isn’t, and the WHO didn’t.) or that eating an egg a day contributes as much to cardiac disease as smoking five cigarettes a day. (Totally overblown.) These claims paint a portrait of veganism as the only truly healthy diet, and that anything else is just slow poison.
Ok, but is veganism really the dietary be-all and end-all? Look into the individual claims and you’re likely to come away confused. Some research (a very small study) links eggs to arterial plaque. But others, including one very large research project in China suggests that eggs may reduce heart disease risk. Science as a whole does a good job of figuring out the world. Individual studies, however, are often wrong, as much as 40 percent of the time. If you want to know what science says about a huge multifaceted question like diet and health, you have to look at a lot of science. So…what does science say about veganism?
Before we answer, let’s stop and acknowledge a couple of things: First, health is isn’t the only, or even the primary reason to go vegan. Ethical and environmental concerns are enough on their own to make someone choose the plant-based path. Two topics deserving of their own articles, so we won’t get into them here. Second, eating vegan doesn’t automatically mean you’re eating well. Nutter Butters are vegan. Not to mention unfrosted Pop Tarts. And even a junk-free vegan diet raises health concerns. When the Academy of Nutrition and Dietetics finally acknowledged in 2016 that vegetarianism and veganism are healthy ways to eat, the group qualified its endorsement by warning that veganism can lead to serious nutritional deficiencies. Greens contain calcium, but your body can only use about 5% of calcium in spinach unless you have sufficient vitamin D in your body, a vitamin that is lacking in the average American diet, much less a vegan’s. Vegans face similar concerns for adequate intake of iron, omega-3 fatty acids, vitamin B12 and as we said, vitamin D. B12 is especially tricky. B12 is almost completely absent from plant-based foods. And multiple studies show that up to 60% of vegans are B12 deficient, which, if severe enough, can lead to numbness, poor balance, depression, paranoia, memory loss, incontinence and a number of other serious problems. And unfortunately, symptoms might not be apparent until you’ve been deficient for years and the damage is irreversible. But you are reading an article from a source that promotes healthful dining, so let’s assume that you would do everything right: take your supplements, get enough calcium and iron, and eat a well-balanced vegan diet. Is going vegan, as many people claim today, the absolute best way to stay healthy? Science’s current answer is far from definitive and isn’t particularly satisfying. Yes, the vegan diet is good for you. There’s pretty strong consensus that it’s one of the best diets, right up there with the Mediterranean diet, the traditional Okinawan diet and the rest of the “Blue Zone” all-stars (which all include animal products). But the best? Maybe. And you’re not likely to get a better answer than that anytime soon.
The biggest, latest, most sophisticated review of research on veganism, veganism and health appeared in 2017 in the journal Critical Reviews in Food Science and Nutrition. The authors identified 86 high-quality studies of vegetarianism and 24 on the vegan diet, covering a total of more than 130,000 vegetarians and 15,000 vegans. The results: Vegetarians and vegans in general have lower BMI (body mass index), cholesterol, and blood sugar. Vegetarians are less likely to be diagnosed with ischemic heart disease (what happens when plaque narrows your arteries), and they have an 8% lower risk of cancer than omnivores. Vegans reap all the benefits of vegetarianism, plus their cancer risk is 15% lower than that of omnivores. That’s all pretty good news. Here are the caveats: Vegetarianism and veganism may protect you from ischemic heart disease, but they don’t seem to offer significant protection from deaths from ischemic heart disease, total heart disease or cancer. And the cancer results, although they align well with what scientists believe about diet and cancer, are based on just two studies. That wouldn’t be enough to get a new drug approved by the FDA; it is enough on its own to justify a big lifestyle change?
Most dietary studies rely on observation. You gather together a bunch of people who are already vegan and a bunch of omnivores, and track what they eat. It turns out that vegans have better lab tests and less disease. But did the veganism cause these effects? That’s surprisingly difficult to prove. For example, vegans have a lower BMI than typical Americans. High BMI contributes to heart disease, diabetes and cancer. So, which was it, the lower weight (which you can achieve without being vegan) or the diet itself? And if it’s the diet, was it the lack of meat, the addition of vegetables, or both? The kind of study required to answer these questions would be a trial where people are randomly assigned to a diet type for a lifetime. And there are some pre-birth influences, in addition to whether we’re breast-fed, and so on. You get the idea. This type of study has never been done, nor will it ever be done. It would never get past the Human Subjects Research Committees (I know, I’ve been on 2).
And, realistically, it doesn’t need to be. Sure, there is a lot we don’t know about the effects of the vegan diet, or the Mediterranean or Okinawan diets or for that matter any of the other contenders. But we do know that all of them seem to be spectacularly better than today’s average American diet. Even if a winner emerges, the final rankings might not matter much when considered next to individual genetic differences, lifestyle choices or even random external events. That said, there is one advantage to going vegan that you might not have thought of. It’s conceptually simple. You’re not thinking about calories or whether your serving of stew has 3 ounces of meat or 6; you’re just dealing with one easy-to-understand (though not always easy to follow) standard: Is it plant-based? So, what moves you? Is it the possible reduction in disease risk? Do you want to do your bit to be kinder to chickens or (maybe) to reduce your carbon footprint of agriculture? Is it that you simply want to eat more vegetables (you know I’m all over that!)? Then you might want to try vegan. But remember this: you need help from a professional to ensure that you’re getting all your essential nutrients. And note that you’re not obeying a scientific imperative. There are no guarantees that there is not a marginally better choice out there, but as of today no one can conclusively tell you what that better choice is, or if it even exists. If you are making the switch, good for you. Sincerely. Don’t let some hyper-carnivorous in-law lure you into an argument at the next family do. (They will.) And, take your B12. It’s important.
Patrick Clinton with edits by Dr. Jan Evans