science and vegan dietsThe latest book to capitalize on anti-veganism is by science writer Mara Kahn (and, yes, of course, she’s also an ex-vegan). It’s called Vegan Betrayal: Love, Lies and Hunger in a Plants Only World. I can’t comment much on the book since I haven’t read it. But I can comment on a review of the book that appeared on the Science Based Medicine (SBM) website.

Written by SBM co-founder Dr. Harriet Hall, it was more a synopsis of the book’s contents than a thorough review. It was also an endorsement for a number of non-science-based myths about vegan diets.

Usually, I find the SBM website to be balanced and evidence-based. Its writers (including Dr. Hall) are smart and insightful and I often agree with their criticisms of popular vegan claims. This article, though, displayed an incredible bias against veganism. Or maybe just a lack of knowledge about vegan diets. Whichever it is, it has no place on a website that prides itself in being evidence-based.

Dr. Hall didn’t claim to like all of the book (more on that below) but she recommends—“highly recommends,” in fact—the part that addresses vegan nutrition. Based on what I saw in her review, I don’t think I agree.

For example, Kahn claims that “Research has shown vegan deficits in many key nutrients including iodine, iron, zinc, taurine, vitamins A, D and B12, selenium, protein, calcium and omega-3 fatty acids.”

We’ve all seen these statements before—the kind that bundle misinformation with misleading observations. For example, vegans have about the same risk for iron deficiency anemia as non-vegetarians. It’s not that this is necessarily a good thing, since iron deficiency anemia is a serious and common problem. But pointing out that vegans might be deficient is misleading if you’re trying to make the case that vegan diets are inferior to those that contain meat.

Also, the last time I checked, taurine was not considered to be a nutrient let alone a “key” nutrient.

It’s true that poorly planned vegan diets can be too low in vitamins A, D and B12, calcium, zinc, iodine, essential omega-3 fats, and (in some parts of the world, but not the United States) selenium. Non-vegetarian American diets have also been found to be low in vitamins A and D, and in calcium, as well as in vitamin E, folate, vitamin C, magnesium and fiber. Meat-eaters over the age of 50 may also be deficient in vitamin B12 if they aren’t using supplements or fortified foods.

So, meat-eaters do better with some nutrients and vegans do better with others. No particular dietary pattern guarantees adequate nutrient intake and therefore this is not an argument for or against veganism. Nor it is an argument for or against diets that include meat. It just means that no matter what dietary pattern you choose, you should pay attention to nutrient intake.

But, Dr. Hall says that Ms. Kahn “observes vegans eating huge amounts of carbs and vegan junk foods and skimping on their protein and vitamin needs.” 

Why would someone writing for a blog called Science-Based Medicine care what a layperson  “observes” when those observations aren’t backed by research? Vegans consume diets that get about 10 to 14% of calories from protein and are about 30% fat—so are not particularly low in either of these macronutrients. Vegans may have higher carb intakes than non-vegetarians but since they also have lower average BMIs and a much lower risk for diabetes, it’s not likely that this is a problem.

And the claim that vegans eat large amounts of junk foods stands in stark contrast to the observation just a few paragraphs later that “vegans may feel better at first simply because they are eating fewer calories and have replaced processed and junk foods with healthier fruits, vegetables, and grains.”

So which is it—are vegans at risk for health problems because they eat so much junk, or do they benefit from the fact that they eat less junk?

And then there is this observation about meeting protein needs: “It may be possible for individuals with naturally lower protein needs who can tolerate large amounts of legumes, lead low-stress lives […] and keep a vigilant eye on daily quantity, quality, and amino acid completeness. Easy? No, it is not.”

Easy? Yes it is. It involves meeting calorie needs and including a few servings of lysine-rich foods like beans, soyfoods, peanut butter or quinoa in your diet every day. You have to be seriously stuck in the 1980s to think that we need to keep a “vigilant eye” on “amino acid completeness.”

Finally, it wouldn’t be a good ex-vegan/anti-vegan article without some fearmongering about soy. Dr. Hall writes: “Vegans often rely on soy for protein, but soy can be harmful to health in various ways.”

But is this Dr. Hall’s opinion or Ms. Kahn’s? As with much of this review, it’s not entirely clear. Either way, it is irresponsible to toss such a vague, unsubstantiated statement into the article without challenging it.

In the comments following the article, a moderator argues that this was a book review, not an article that shares Dr. Hall’s opinions. But the fact is that Dr. Hall does get around to criticizing some of the content of the book in a section she titles “Woo Intrudes.” Here she challenges Kahn’s opinions on GMOs, statins, and fructose as “alarmist and not based on rigorous science.” Why didn’t she likewise challenge the section on vegan nutrition in this way? It’s because she believes that “on the subject of veganism, Kahn’s information is evidence-based and reliable and her reasoning plausible.”

As far as I can tell, it’s none of the above. But, I must admit, there are some legitimate criticisms in the book and in the review. It is fair to challenge vegans who claim that humans evolved as herbivores. We didn’t; we’re omnivores who have the option to eat herbivorously. It’s legitimate to accuse vegans of over-reaching if we claim that a vegan diet is the only healthy way to eat. The evidence doesn’t support that, and it’s likely that there are other plant-based patterns that are as healthy.

Had the book and the review stuck to those kinds of issues, the criticisms would have been valid.  But for both sides of the discussion—pro- and anti-vegan—bias and misinformation and half-truths trip us up. We vegans need to avoid that. And the Science-Based Medicine website owes its readers an actual science-based review of Ms. Kahn’s book.