In January 2020 Zaria Gorvett published an article titled "How a vegan diet could affect your intelligence" for the BBC. The article is ridiculous.
Claim
On the one hand, recent concern about the nutritional gaps in plant-based diets has led to a number of alarming headlines, including a warning that they can stunt brain development and cause irreversible damage to a person’s nervous system.
Response
The statements here seem to be very different from the tone of the articles cited to support them. The articles discuss warnings from "nutritionists" on the dangers of vegan diets for children but make it clear that a vegan diet is still safe if done properly. The article cited to support claims regarding brain develeopment, for example, cited a single nutritionist but goes on to say:
But other nutritionists have said that a plant-based diet can provide plenty of choline, and pregnant vegans have the options of using supplements. Critics have also pointed out that Derbyshire has provided consulting for the Meat Advisory Panel and the British Egg Information Service, listed as "competing interests" in the published article.
....
Most health experts concur that plant-based eating is not only safe, but optimal for health. "You do not need to take a choline supplement when you switch to totally plant-based nutrition if you eat a balanced and varied diet containing plenty of minimally processed plant foods. The evidence base shows that this way of eating can support excellent health," Russell said in the statement. This is consistent with information from British Dietetic Association. "You absolutely can meet the requirements with a vegan or plant-based diet," spokeswoman Bahee Van de Bor told the BBC. She added that good planning can help make sure a diet is nutritious, and picky eaters may want to consider a choline supplement.
Choline will be discussed further later on, but this article clearly concludes that vegan diets are just fine. The second article cited regarding nervous system damage quotes two professors with no degrees in the area of nutrition or dietetics while providing no citations.
Claim
Back in 2016, the German Society for Nutrition went so far as to categorically state that – for children, pregnant or nursing women, and adolescents – vegan diets are not recommended, which has been backed up by a 2018 review of the research.
Response
The German Society for Nutrition have actually changed their position since then to endorse vegan diets for adults, and not recommend against (OR in favor of) the diet for children, pregnant or nursing women, and adolescents, instead leaving the decision up to individuals.
The 2018 review of the research was published before much of the more recent work on plant-based diets in children and pregnant women, particularly among vegans.(1)(2)(3)(4)(5)(6) Importantly, this review was a "narrative review", meaning the author could pick and choose which studies to include rather than systematically searching through the literature for all relevant publications. This may be why two excellent studies on vegan children available at the time were omitted.(7)(8)
The sole author of the review, Nathan Cofnas, points to a 2000 study reporting a low male-to-female sex ratio among babies born to vegetarian mothers, interpreting this as evidence of potential problems with vegetarian diets. However, aside from smoking, the study did not account for lifestyle, dietary, or other potential confounding factors such as energy intake, body weight, age, or socioeconomic status.
Cofnas then discusses a study that found that males born to vegetarian mothers were significantly more likely to have hypospadias, a genital deformity. Yet, these findings were not replicated in a more recent and larger study that found no such link.(9) Additionally, although Cofnas asserted the effect was due to the consumption of high-phytoestrogen legumes, the cited study's results concerning soy products were not statistically significant. This conclusion is further challenged by a newer study reporting an inverse relationship—phytoestrogen intake was associated with a lower incidence of hypospadias.(10)
Cofnas further claims that, even with supplementation, vegans may remain at risk of vitamin B12 deficiency due to a study finding insufficient levels of B12 in vegans who were vitamin users. Yet these were people who "supplemented their diet with B vitamins", not necessarily B12, with no data provided on frequency or dosage. Other studies have found sufficient B12 levels in supplementing vegans.(11)(12)(13)
Claim
After the Royal Academy of Medicine in Belgium decided a vegan diet was “unsuitable” for children, parents who force a vegan diet on their offspring in Belgium could even one day find themselves in prison.
Response
If this is meant to be an actual argument against vegan diets for children then it is simply an appeal to legality. Laws have no bearing on nutrition science.
Claim
Instead, the only research that comes close involved the reverse. It was conducted on 555 Kenyan schoolchildren, who were fed one of three different types of soup – one with meat, one with milk, and one with oil – or no soup at all, as a snack over seven school terms. They were tested before and after, to see how their intelligence compared. Because of their economic circumstances, the majority of the children were de facto vegetarians at the start of the study. Surprisingly, the children who were given the soup containing meat each day seemed to have a significant edge. By the end of the study, they outperformed all the other children on a test for non-verbal reasoning. Along with the children who received soup with added oil, they also did the best on a test of arithmetic ability. Of course, more research is needed to verify if this effect is real, and if it would also apply to adults in developed countries, too. But it does raise intriguing questions about whether veganism could be holding some people back.
Response
Speaking of congitive function, I'm not sure the individual who wrote this has much. How were these results suprising to Gorvett?
These children were in a third world country (in 1998!) with likely inadequate nutrition. Obviously, giving them meat (a whole food with multiple macro- and micronutrients) gave them a significant edge compared to what is basically isolated vegetable fat (with a single macronutrient and abysmal amounts of a couple micronutrients). This is not remotely close to being relevant to veganism. Oil is not representative of a vegan diet. How about trying soup with some type of legume, whole grain, or tofu? This study does not raise a single question, and definitely no intriguing questions, about veganism. This is an incredibly pathetic argument.
Claim
Others are found in vegan foods, but only in meagre amounts; to get the minimum amount of vitamin B6 required each day (1.3 mg) from one of the richest plant sources, potatoes, you’d have to eat about five cups’ worth (equivalent to roughly 750g or 1.6lb). Delicious, but not particularly practical.
Response
Fascinating, the BBC seems to be under the impression that individuals get all their daily needs of a nutrient from a single food. And, anyway, their numbers are way off. For baked potatoes, it only takes 419 g with skin, and 432 g without skin to get 1.3 mg of Vitamin B6. Similarly, for boiled potatoes, 435 g with skin, and 484 g without skin can supply your daily needs.
Individual foods rarely provide 100% of the daily requirements of a particular nutrient, because they don't need to; You can eat just 150 g of baked potato with skin, if you wish, and that would supply 36% of your daily requirement of Vitamin B6. And just a single banana would supply another 19%, with a small apple contributing 5%, and 10 walnut halves providing another 10%. These might seem like small amounts but I'm already at 70% of B6 needs with not even 500 calories. Once again, no one needs to eat 700 grams, 400 grams, or any amount of potatoes, because diets tend to consist of more than one food.
And as if their argument couldn't get any more laughable, studies tend to find HIGHER intakes of Vitamin B6 in vegans compared to meat-eaters,(14) with both a 2017 and 2020 study finding blood levels in vegans way above the cutoff for deficiency and similar to those of meat-eaters.(11)(13)
Claim
Even so, low B12 is widespread in vegans. One British study found that half of the vegans in their sample were deficient. In some parts of India, the problem is endemic – possibly as a consequence of the popularity of meat-free diets.
Response
Tha's what supplements are for. This is also the same Vitamin B12 study previously discussed that did not properly assess supplementation habits.
Claim
It’s surprisingly easy to slip into iron deficiency, even though it makes up 80% of the inner mass of the planet we live on. Up to two billion people are thought to have a shortage of the element worldwide, making it the most common nutritional inadequacy. Vegans are particularly prone, because the form that’s most readily absorbed by the body is “haem iron”, which is only found in animal proteins. One German study found that 40% of the vegans they looked at were consuming less than the recommended daily amount.
Response
That study is from over 20 years ago, with German studies from both 2020 and 2023 finding sufficient intake and status in vegans.(13)(15) The 2020 German study also assessed prevalence of deficiency with only 11% of vegans showing signs of iron deficiency. The rate in omnivores wasn't much lower at 8%. I didn't even have to change countries, all I did was not look at a single study from 2004. Crazy, right?
Claim
Though there are small amounts of taurine in some dairy products, the main dietary sources are meat and seafood. “Some species have the ability to make all the taurine they need,” says Jang-Yen Wu, a biomedical scientist at Florida Atlantic University. “But humans have a very limited capacity to do this.”
Response
What is being defined as a "limited" capacity and why is no evidence provided for this claim? Ok, go on.
For this reason, vegans tend to have less taurine in their bodies. No one has looked into how this might be affecting their cognitive abilities yet...
Let me stop you right there. No one has looked into it, right? So stop speculating.
but based on what we know about its role in the brain, Wu says vegans should be taking taurine tablets. “People can become deficient when they restrict their diets, because vegetables have no taurine content,” he says.
The most obvious method to test their theory that vegans suffer cognitive deficits as a result of lower taurine would be to study the cognitive health of vegans. But perhaps Gorvett though an article about brain health in a particular group didn't need to include any studies about brain health in that particular group? Associations between plant-based diets and dementia risk have shown either protective or neutral associations,(16)(17) whereas differences in cognitive outcomes have not been observed.(18)(19) Additionally, trials purporting to find cognitive benefits of taurine supplementation utilize doses several times what can be reasonably achieved from any food sources. If anything, Wu's recommendation for taurine tablets should be for everyone, vegan or not.
Claim
In fact, the holes in our current understanding of what the brain needs to be healthy could potentially be a major problem for vegans, since it’s hard to artificially add a nutrient to your diet, if scientists haven’t discovered its worth yet.
“There are so many unknowns,” says Nathan Cofnas, who has authored a review on the subject. “And when you deviate from the typical diet for your species, to one which has not been tested and properly established to be healthy or good for the brain, you are conducting an experiment and you are taking a risk.”
Response
What a ridiculous, speculative thing to say. What if it's the other way around? What if we were to discover a nutrient only available in plants, that you can only achieve sufficient intake of by consuming a diet very heavy in plant foods? Both arguments are just as speculative and ridiculous.
And most importantly, who cares? If there is some hypothetical undiscovered meat-only nutrient then this should be reflected in health outcome studies. Rather then speculating, maybe provide evidence that vegans suffer some unexplainable impairment or negative health outcome, which is what we should expect if there was an undiscovered nutrient that vegans are deficient in. If no such data exists, then clearly this mysterious magical nutrient is very insignificant.
Claim
There are small amounts of choline in lots of vegan staples, but among the richest sources are eggs, beef and seafood. In fact, even with a normal diet, 90% of Americans don’t consume enough. According to unpublished research by Wallace, vegetarians have the lowest intakes of any demographic. “They have extremely low levels of choline, to the point where it might be concerning,” he says.
Response
Choline has no established Recommended Dietary Allowance (RDA). When an RDA is set for a nutrient it is intended to be the average daily intake level sufficient to meet the nutrient requirement of nearly all the population. Instead, something called an Adequate Intake (AI) has been established for choline, which typically happens when there is insufficient evidence to establish an RDA. In this case, 'insufficient' would be an understatement. To quote veganhealth.org:
The AI for choline is 550 mg/day for men and 425 mg/day for women but these numbers are based on very limited data. They are derived from a 1991 study at the University of North Carolina at Chapel Hill (Zeisel, 1991). When subjects consumed 50 mg or less of choline per day, they experienced markers of deficiency such as increased liver enzymes, a fatty liver, or elevated creatine phosphokinase (CPK) which indicates muscle deterioration. The deficiency symptoms resolved when the subjects were given supplements providing 500 mg of choline per day. The study didn’t look at the effects of choline intakes between 50 and 500 mg.
A more accurate statement would be that 90% of Americans don't meet the AI for choline, but whether they consume enough or not is a different question.
Claim
For vegans, the picture is likely to be bleaker still, since people who eat eggs tend to have almost double the choline levels of those who don’t. And though the US authorities have set suggested intakes, they might be way off.
Wallace points to a 2018 study, which found that the babies of women who consumed twice the amount considered “adequate” – around 930mg each day – in the last third of pregnancy enjoyed a lasting cognitive edge. For comparison, the average vegetarian gets roughly a fifth of that amount.
Response
Saying they "consumed" twice the amount is somewhat misleading—they supplemented it. After all, it's not just vegetarians who get only a fraction of that amount from diet alone. As they themselves said earlier, over 90% of Americans fail to meet recommendations for even half that amount. Reaching the intake in the study through food alone would require more than seven medium eggs—nearly 500 calories. As with taurine, it's beginning to sound as if their concerns apply to vegans and non-vegans alike.
If lower choline intake in vegans actually led to choline deficiency, we'd expect to see a higher risk of liver problems in those consuming low amounts of animal products, which is the main concern with low choline. Yet, those consuming the highest amounts of healthy plant foods and the lowest amounts of animal products have a lower risk of non-alcoholic liver disease.(20) And as noted earlier, associations between plant-based diets and dementia risk have shown either protective or neutral associations,(16)(17) whereas differences in cognitive outcomes have not been observed.(18)(19)
Claim
“I tell people all the time, if you're going to be a vegan or vegetarian, that's fine,” says Wallace. “I’m certainly not advocating against it. But there are 40 or something essential nutrients. So, I mean, it really would take a lot of research for vegans to get everything the brain needs,” he says. Some nutrients that a typical vegan diet is low or lacking in, like choline, creatine, carnosine and taurine, are extremely bulky, so just taking a standard vitamin tablet won’t be enough. Instead, they need to be taken individually.
Response
Every diet requires planning. While vegans may be at risk of inadequacy for vitamins B12, D, iodine, iron, and zinc, meat-eaters may be at risk of inadequacy for vitamins, D, E, fiber, folate, and magnesium. Vegans also tend to have particularly favorable intakes of vitamins B1, B6, and C.(14) Their arguments for why vegans should be taking choline, creatine, and taurine supplements all apply to non-vegans as well. As for carnosine, they haven't elaborated on it once throughout the article.
Claim
Cofnas takes a harsher view. Though vegans can take supplements, he thinks it’s unrealistic to expect that they all will. Consequently, he finds the recent shift towards plant-based diets troubling, though he’s sympathetic to the arguments for doing so. “Without question, veganism can cause B12 and iron deficiencies, and without question they affect your intelligence,” he says.
Response
The keyword here is "can cause". Yes, of course they can cause deficiencies, no one in their right mind is denying that! Literally any diet can cause deficiencies, with estimates of iron deficiency among Americans standing at 14-15%.(21) Vegans, on average, have adequate iron status. The same is true of vitamin B12 with proper supplementation.(11)(12)(13)
Claim
An earlier version of this article stated omega-3 generally only occurs in animal products. The article has been corrected to make clear there are three types of omega-3 fatty acids and that one of these, ALA, is found mainly in plants.
The article also stated that Nathan Cofnas was a biologist at the University of Oxford. He is in fact studying philosophy of biology at the University of Oxford and has co-authored studies looking at the impact of the vegan diet on health and the brain. The article has been corrected to reflect that.
Response
Wow, he sure sounds like an expert. You should keep quoting him on articles about nutrition in the future, I think he's really qualified for that.