Bad Intel: Is There Evidence a Vegan Diet Negatively Impacts Intelligence?
The BBC published an article suggesting that eating a vegan or vegetarian diet can affect your intelligence in a negative way. Nearly every claim is either totally untrue or misleading.
Besides using debunked or outdated opinion pieces and studies to make her case, the author also appealed to false authority (citing a philosopher of biology — not a biologist; and relying heavily on the opinion of Taylor Wallace, who’s written about the benefits of drinking milk, supports industry-funded research, and criticized the EAT-Lancet report for its suggestion to reduce meat consumption for planetary and individual health), appeal to emotion (citing tabloid articles about vegan diets causing developmental problems in children; Gandhi failing the vegan diet to help evoke a negative emotional memory), and appeal to ignorance (citing no evidence lower creatine/taurine levels in vegans is bad, but should be a concern anyway). This further confuses a public already disoriented by the constant mixed messaging from conflicting studies and health professionals at odds with each other.
And speaking of sowing confusion, this article comes as a number of questionable recommendations and studies have been published in the US promoting red meat consumption, egg consumption, choline, and dairy products (we have plenty of data that all these things are detrimental to health) with the US Food Guideline set to change in 2020.
Before we get into it, let’s be clear: a plant based diet is the only diet clinically proven to prevent and mitigate the symptoms of heart disease, some cancers, and type 2 diabetes — the top causes of death around the world. CVD in particular is the leading cause of death globally. It accounted for more than 17.6 million deaths in 2016 and is expected to rise to more than 23.6 million by 2030.
When it comes to cognitive health, many studies show the further we move away from animal-products the better people do. In fact, studies find those consuming meat (including fish and poultry) had twice the risk of developing dementia compared to vegetarians. Saturated fat and cholesterol can create plaque in the veins that run to your brain the same way they do to your heart.
Let’s go through the arguments one by one and give everything a closer look.
“Meat Made Us Human”
The theory is that cooking meat made our brains bigger on our road to evolution. As it turns out, our brains run mainly on carbohydrates (glucose) and we developed a special enzyme in our saliva called AMY-1 that helped us break down compounds in complex carbohydrates around the same time we learned to cook. It was this, not eating meat, that set the ball in motion. Furthermore, despite being able to digest meat as omnivores, had we really ‘evolved’ to eat meat and other animal products then we wouldn’t still be developing heart disease, cancers, and diabetes after eating too much of it. The outdated study cited in the article says Neanderthals ate mostly meat and it was meat that developed the brain, but more research has come out concluding that they ate far more plant-foods than previously thought.
The author also linked India’s generally lower IQ levels to the fact that the country is largely vegetarian. This assumption, which is not specifically backed up by solid data, overlooks the fact that India’s lower IQ levels are said to be from widespread malnutrition in general. In fact, 25% of all hungry people in the world live in India. Additionally, the author does not point out that, despite malnutrition problems, dairy consumption has spiked in recent years. India has become one of the world’s leading milk producers, exceeding 100m tonnes in 2006. And dairy, according to the experts in the BBC article, is touted as full of vitamins and minerals needed for proper brain development.
Sensationalism
Next, the author brings up sensationalized tabloid stories about parents feeding their children vegan diets which caused permanent developmental issues. If followed to their sources, many of these stories reveal the child wasn’t breast feeding and was only being given a homemade vegetable porridge, or unfortified soy milk instead of baby formula. These anecdotes –which are very rare — are often sensationalized and appeal to emotion without science.
Many leading health organizations including the American Academy of Pediatrics, Kaiser Permanente, and the Academy of Nutrition and Dietetics conclude a properly planned vegan or vegetarian diet is suitable for all stages of life, including pregnancy and infancy.
The author also mentions the Royal Academy of Medicine of Belgium’s opinion that will make it possible to imprison parents who enforce a vegan diet on their children. This assessment has also been roundly debunked by the scientific community. Plant based diets are also associated with reduced risk of chronic respiratory disorders, allergies, and recurrent infections in childhood.
The Kenya Study
The only actual evidence the author provides that suggests eating a plant-based diet can negatively impact your intelligence is a study done on 500 children in rural Kenya in 2003. The conclusion was that the more dairy and meat added to a child’s diet resulted in better cognitive performance. But there were some issues with the methodology. The study was not blinded and was conducted on underweight children who generally didn’t receive school meals. In fact, the diet given to the ‘plant based’ group lacked in energy, carbohydrates, fat, and protein to begin with. Poor education and poverty was also not factored into the study.
The Kenya study was also funded the Global Livestock Collaborative Research Support Program and the Office of Agriculture and Food Security, and the findings were presented at the “Animal Source Foods and Nutrition in Developing Countries”. A conflict of interest the author did not mention.
Next, the author throws out a slew of nutrients she says are unobtainable or nearly unobtainable on a vegan or vegetarian diet including: choline, creatine, carnosine, taurine, omega-3, haem iron and vitamins B12, B6, and D3. So, let’s talk about these.
Let’s Talk About Choline
Choline concern is a recent thing. Emma Derbyshire, who is paid by the Meat Advisory Panel, wrote a recommendation for consuming more choline despite there being no reliable clinical trials. (There are only three studies looking at choline consumption and cognitive development during pregnancy. The methodology of two of those studies were questionable. The third study was inconclusive. That didn’t stop Wallace from citing it in the BBC article, however.) Instead, there’s emerging data suggesting more choline consumption can lead to cardiovascular disease. The recommendation that spurred the choline scare suggested vegans and vegetarians didn’t get enough choline in their diets.
It’s important to note there’s no true consensus on choline consumption in the first place, only a recommended ‘adequate intake’ because the evidence is insufficient to develop an RDA.
Choline being hard to come by for vegans and vegetarians is also generally untrue. A significant portion of choline is made by the body. Cruciferous vegetables and certain beans are also rich in choline, and other dietary sources of choline include nuts, seeds, and whole grains.
Higher dietary choline — especially from animals sources like eggs that come with cholesterol — increases CVD risk because some choline and carnitine, are converted to trimethylamine (TMA) by intestinal bacteria. TMA is converted by the liver into trimethylamine-N-oxide (TMAO), a compound linked to a higher risk of cardiovascular disease. However, more rigorous data is needed on choline moving forward.
Reminder: heart disease — not choline deficiency — is still the top cause of death in men and women around the world. And choline in particular has been found to increase that risk.
Next Up is Taurine
We make taurine in our bodies from cysteine. If we eat enough protein each day, then we get enough cysteine to provide enough taurine. Furthermore, there’s no data that shows lower taurine levels compromises our health in any notable way.
The article states, “…vegans tend to have less taurine in their bodies. No one has looked into how this might be affecting their cognitive abilities yet…”
There’s also no scientific evidence of wide-spread taurine deficiency among vegans, just lower amounts. But again, planting a seed of doubt is all that’s required here: creating a crisis out of an amino acid you never heard of.
Heme Iron
The article says iron is scarce in a vegan diet. This is also misleading. The author writes, “Vegans are particularly prone, because the form that’s most readily absorbed by the body is “heme iron”, which is only found in animal proteins.”
Heme iron is easily absorbed in animal products because it comes with cholesterol. It also increases your risk of diabetes and heart disease, but the author omits this. In fact, heme iron was found to be an independent risk factor for all-cause mortality.
Non-heme iron is relatively easy to come by in a vegan diet. And several studies have found that in general vegans are not more anemic than meat eaters. In fact, some studies show plant based diets tend to be higher in iron than other diets. But iron is still a nutrient of concern. In the US, about 10 million people (not vegans specifically) are iron deficient, including 5 million who have iron deficiency anemia. There are 1.6 billion people are anemic globally.
Once Again… B12
Misleading. Yes, some studies have shown vegans having lower B12 levels, but nearly 40% of Americans (not vegans) are B12 deficient. People on plant based diets should be taking a supplement (which are widely available)… but so should everyone else. Again, it’s not a vegan issue. It’s an issue worldwide. B12 is made by microorganisms, bacteria, fungi, and algae. At one time there was enough B12 in rivers and soil to obtain what we needed, but because soil no longer has the same nutritional makeup it once had and because of rigorous food washing practices, plant foods are no longer a reliable source. Additionally, animals and animal products are supplemented with B12 and are not reliable sources.
B6
Vitamin B6 deficiency is uncommon in general. It’s only an issue in places where poor nutrition is widespread. Some studies have indicated that vegans do exhibit signs of deficiency, but they are rare. Other studies have found vegetarians get more B6 than the general population. Sources of B6 include nutritional yeast, fortified plant milks and cereals, barley, soy products, mushrooms, spinach, sea vegetables, and beet greens.
The article argues that getting enough B6 is difficult for vegans, by suggesting that a cup of potatoes is only 20% of the RDA. It says eating five cups of potatoes would be impractical. But you can also just eat other things… like a cup of chickpeas (more than 50% of the RDA), some spaghetti (one cup of marinara sauce is 20% of the RDA), beans, bread, a banana (20%)…
D3
Again inaccurate. It’s not just a vegan problem. It’s a global concern. About 70–97% of Americans are lacking in vitamin D. Vegans and meat eaters have the same risk. If five minutes of sunlight isn’t an option, or you live far from the equator, a supplement works. Otherwise plant milks, fruit juices, cereals, breads, and pastas can all be fortified with Vitamin D.
Next is Creatine
The brain largely makes its own supply and there’s no conclusive data that vegans and vegetarians need to consume more than the average omnivore. But adding this into the laundry list of concerns helps muddy the waters, even if author admits there’s no evidence.
Carnosine, Omega-3, Selenium, Folate, and Iodine are next
But the author doesn’t mention these again after bringing them up once. Like creatine, they’re listed as nutrients vegans and vegetarians have trouble getting, and then not explained or sourced.
Carnosine is a protein building block made from two amino acids (alanine and histidine). Our bodies make it. There is some emerging data that suggests lack of carnosine could lead to brain-related disorders. But these are animals studies. There is a study that found vegetarians had lower levels than meat eaters, but no evidence linking carnosine to brain-related disorders in vegans and vegetarians.
The jury is out on Omega-3 (DHA) is still out. Generally, there’s plenty of plant based sources of ALA (you can get the RDA from just a tablespoon of ground flaxseed), but the conversion to DHA and EPA isn’t always reliable. Taking an algae-based DHA is recommended. The ratio of Omegas is also important. Most fish sources of DHA come with a problematic Omega-3 to Omega-6 ratio that promotes inflammation.
And when it comes to pregnancy, higher levels of mercury found in mothers who eat more fish has been associated with birth defects, seizures, developmental disabilities, and cerebral palsy. All of this was not mentioned in the article.
Selenium is an essential trace mineral. Brazil nuts are great sources — with one ounce containing 777% of the RDA. Other sources contain whole grains, legumes, most vegetables, seeds, and other nuts.
Iodine deficiency — like B12 and iron — is not exclusive to vegans. It’s a global health concern as it affects about one in three people. There is some data that shows there’s an increased risk for vegans, but it is easily managed with fortified plant milks and cereals, sea vegetables, potatoes, and iodized salt.
And finally, why folate is listed is a mystery. There’s plenty of folate-containing plant foods. The word folate even comes from the Latin for “leaf” because leafy greens are a good source of this nutrient.
Cognitive Issues Later in Life
Now, besides the data on dementia, the article also leaves out some other key findings in terms of cognitive health, including high-fat diets, low-carbohydrate diets (ones low in plant foods and high in animal products) impair cardiac high-energy phosphate metabolism and cognitive function. Researchers also found that eating as little as 1⅓ cups of lettuce daily — or a bit more than half a cup of cooked dark leafy greens — can delay memory decline and thinking skills that occur with age. In fact, they found leafy green fans had brains that functioned as well as people 11 years younger.
Meantime, if you are looking to raise a child plant based, there are several tools available, including this guide for health care providers, the American Academy of Pediatrics guide, the Academy of Nutrition and Dietetics guide, and easily digestible resources from the Physicians Committee for Responsible Medicine.
