Vegan Diet and Brain Health: Risks, Benefits, and How to Optimize

Short answer: A well-planned vegan diet with a reliable B12 source is compatible with brain health; without B12, it poses real neurological risks. Possible benefits come from polyphenols, fiber and better heart health, but direct evidence on brain outcomes is limited (graded Preliminary). Take B12, consider algal oil for DHA, and plan for choline, iodine, iron and vitamin D.

A vegan diet is neither better nor worse for the brain by default. What decides it is whether you cover a handful of nutrient gaps. The possible benefits come from eating lots of plants, which is linked to lower inflammation and better heart health, but studies of brain outcomes in vegans are scarce.

The risks are better established. Vitamin B12 deficiency, common in vegans who don’t supplement or eat fortified foods, can cause nerve damage and cognitive problems that don’t always reverse. DHA, the main omega-3 fat in the brain, is missing from vegan diets unless you take algal oil.

Before starting supplements, ask a doctor, pharmacist or dietitian, especially if you are pregnant, breastfeeding, take medication or have a health condition.

What vegans need to cover

Vitamin B12: the one supplement every vegan needs

Vitamin B12 is the most important nutrient concern for vegans. The body needs it to build and maintain myelin, the protective coating on nerve fibers, and to make brain chemicals.

There are no reliable plant sources of B12. Spirulina, nori, tempeh and unfortified nutritional yeast contain B12 look-alikes that don’t work in humans and may interfere with real B12 absorption. The Academy of Nutrition and Dietetics states that vegans need reliable B12 sources, such as fortified foods or supplements (Melina 2016).

What B12 deficiency does

B12 deficiency can damage the spinal cord by stripping the myelin from nerve fibers. It can also affect the brain and the nerves in the limbs. Signs include numbness or tingling, balance problems, memory loss, poor concentration, confusion, personality changes, depression and, in severe cases, dementia. The damage from long-term deficiency can be permanent, even after treatment starts.

Healton and colleagues (1991) reviewed 153 episodes of B12 deficiency affecting the nervous system in 143 patients. Nerve symptoms, most often tingling or unsteadiness, usually came first; dementia, psychosis and mood problems also occurred. In 27% of episodes the blood count was normal, and recovery after treatment was complete in under half. So you can’t rely on anemia as an early warning: the nerves can be damaged before the blood shows any sign.

In the EPIC-Oxford cohort, 52 percent of 232 vegan men were B12 deficient (serum B12 below 118 pmol/L) (Gilsing 2010). That compared with 7 percent of vegetarians and one of 226 meat-eaters.

In practice: use fortified foods or a supplement taken daily or weekly. Cyanocobalamin is the most stable and best-studied form. No upper limit has been set for B12, but some medicines (such as metformin and acid-reducing drugs) lower B12 absorption. Ask a doctor or pharmacist which regimen suits you and whether your B12 should be checked. Our B vitamins guide has more.

DHA and EPA: algal oil fills the gap

DHA makes up a large share of the fats in the brain’s outer layer and is important for nerve cell membranes and the junctions between neurons. EPA works mainly through anti-inflammatory pathways.

Vegan diets contain no ready-made DHA or EPA. They do contain ALA, a plant omega-3, from flaxseeds, chia, hemp seeds and walnuts. But the body converts ALA to DHA very poorly. Studies using labeled fats show that men convert little ALA to EPA and very little on to DHA; women convert somewhat more, possibly because of estrogen (Burdge and Calder 2005). Eating more ALA raises blood EPA but not DHA.

Sarter 2015 studied 165 long-term US vegans. Their average omega-3 index (DHA plus EPA in red blood cells) was a low 3.7%, similar to omnivores who eat little fish. In 46 vegans with an index below 4%, an algal supplement providing 254 mg of DHA plus EPA a day for 4 months raised it to 4.8%.

Algal oil comes from microalgae and supplies the same DHA that fish get through the food chain. In the MIDAS trial (Yurko-Mauro 2010), 485 healthy adults aged 55 and over with age-related memory complaints took 900 mg a day of algal DHA or placebo for 24 weeks. DHA improved a visual learning and memory test but not working memory or executive function. Evidence that omega-3 supplements improve cognition in healthy people is mixed. There is no evidence that the source of DHA (algae or fish) changes how it works.

Like fish oil, omega-3 supplements can increase bleeding risk with anticoagulant or antiplatelet drugs. Doses above about 1 g a day have been linked to a higher risk of atrial fibrillation in trials. Ask a doctor or pharmacist before starting one. See our omega-3 guide for more.

Choline

The brain uses choline to make acetylcholine, a messenger involved in memory, and to build cell membranes. The richest sources are eggs, liver and fish, all absent from a vegan diet. Soybeans, quinoa, broccoli and Brussels sprouts contain choline, but much less per serving.

Most Americans eat less than the Adequate Intake (550 mg a day for men, 425 mg for women). Vegans probably eat less than average, though direct data are limited. Good vegan sources include soy foods (edamame, tofu, tempeh), quinoa, potatoes, cauliflower and peanuts. Meeting the full target takes planning.

Some people use choline supplements such as citicoline or alpha-GPC. The adult upper limit for choline is 3,500 mg a day, and supplements can interact with medicines, so ask a doctor or pharmacist first.

Iron, zinc, iodine and vitamin D

Iron and zinc. Plant diets can supply enough iron and zinc on paper, but the body absorbs less of them. Plant (non-heme) iron is absorbed less well than iron from meat, and phytates in whole grains, beans and nuts reduce absorption of both iron and zinc. The brain needs iron to make dopamine and serotonin, and iron deficiency, even without anemia, has been linked to poorer attention and fatigue. Vegans need about 1.8 times as much iron as omnivores for the same iron status (Institute of Medicine 2001). Eating vitamin C-rich foods with iron-rich meals greatly improves absorption. If you are worried about your iron, ask your doctor about a blood test; take iron supplements only if advised, as excess iron can be harmful.

Iodine. The thyroid needs iodine, and thyroid hormones regulate brain metabolism and development. Dairy and seafood are the main sources in Western diets, so vegans who don’t use iodized salt may be at risk. In EPIC-Oxford, vegans had the lowest estimated iodine intakes, suggesting widespread inadequacy (Sobiecki 2016). A UK study of 30 vegans using duplicate meals and urine tests classed them as at risk of deficiency (Lightowler and Davies 1998). The adult recommended intake is 150 mcg a day, which iodized salt or a supplement can provide. The adult upper limit is 1,100 mcg a day. Seaweed and kelp products can contain far more than this, and people with thyroid conditions should ask a doctor before taking iodine.

Vitamin D. Deficiency is common in all diet groups and more so in vegans, who avoid the few foods with useful amounts (fatty fish, fortified dairy, egg yolks). Sources are sunlight, fortified foods or a supplement (lichen-based vitamin D3 is vegan). The adult recommended intake is 600 IU a day (800 IU over 70), and the upper limit is 4,000 IU a day. Current guidance (Endocrine Society 2024) advises against routine vitamin D testing and high doses in healthy adults. Trials of vitamin D supplements for cognition have not shown clear benefit.

Creatine: optional

The liver and kidneys make creatine, but meat and fish add to the body’s stores. Vegetarians and vegans have lower muscle creatine than omnivores (Benton and Donohoe 2011). In the brain, creatine acts as a quick energy reserve.

In a study of 45 young adult vegetarians (Rae 2003), creatine (5 g a day for six weeks) improved working memory and intelligence test scores. There was no omnivore group. Benton and Donohoe (2011) gave 128 young women 20 g of creatine or placebo for 5 days. Creatine improved memory in vegetarians but not in meat-eaters, and had no effect on verbal fluency or alertness.

These are small, short trials, so the evidence is preliminary. Creatine is generally well tolerated in healthy adults, but people with kidney disease, or who take medication, should ask a doctor first. See our guide to creatine for brain function.

Possible brain benefits of a vegan diet

Polyphenols

Well-planned vegan diets tend to supply more polyphenols than omnivorous diets. These are found in berries, leafy greens, tea, coffee, cocoa, nuts and colorful vegetables. Flavonoids are a major group of polyphenols. In lab and animal studies, and some small human studies, they have been linked to better blood flow to the brain, lower inflammation and higher BDNF. BDNF is a protein that supports brain cell growth.

In the Nurses’ Health Study, among 16,010 women aged 70 and over, those who ate the most blueberries and strawberries had slower cognitive decline over about six years. The difference was equal to delaying cognitive aging by up to 2.5 years (Devore 2012). This is an observational finding.

Lower inflammation

Long-term, low-grade inflammation is thought to contribute to cognitive decline, depression and neurodegenerative disease. A meta-analysis (Craddock 2019) included 30 observational and 10 intervention studies. In the observational studies, vegetarian-based diets were linked to lower CRP, fibrinogen and white blood cell counts; there were too few data to pool the intervention studies. This was inflammation in the body, not in the brain.

Fiber and gut bacteria

Vegan diets are usually much higher in fiber. Fiber feeds gut bacteria that produce short-chain fatty acids such as butyrate, which has shown protective effects in animal brains. Berding 2023 ran a 4-week trial in 45 healthy adults. Perceived stress fell by 32% on a diet high in prebiotic and fermented foods and by 17% on the control diet. The difference between groups was not significant, and changes in gut bacteria were subtle.

Heart and blood vessel health

Vegetarian and vegan diets are linked to lower blood pressure, LDL cholesterol, type 2 diabetes rates and BMI (Melina 2016). In a meta-analysis (Yokoyama 2014), vegetarian diets lowered systolic blood pressure by about 5 mm Hg in 7 controlled trials. They were linked to about 7 mm Hg lower pressure in 32 observational studies.

A cross-sectional analysis looked at 11,004 EPIC-Oxford participants (Appleby 2002). Self-reported high blood pressure was 5.8% in male vegans versus 15.0% in male meat-eaters (7.7% versus 12.1% in women). This was largely explained by differences in body weight. Midlife high blood pressure is one of the strongest modifiable risk factors for dementia, so this advantage is relevant to the brain.

What the large cohort studies show

EPIC-Oxford has followed about 65,000 people in the UK since the 1990s, including many vegetarians and vegans. Over 18 years, vegetarians (including vegans) had a 22 percent lower rate of ischemic heart disease than meat-eaters (Tong 2019). But they had a 20 percent higher rate of total stroke, mostly hemorrhagic stroke, about three more strokes per 1,000 people over 10 years. Possible explanations include lower blood cholesterol and lower levels of some nutrients, such as B12. Plant-based diets are not uniformly better for blood vessels.

The Adventist Health Study-2 enrolled over 96,000 Seventh-day Adventists in the US. Among 73,308 followed for about six years, vegetarians as a group had 12 percent lower death rates than non-vegetarians. For vegans the estimate was 15 percent lower, but this was not statistically clear (Orlich 2013). Adventist vegans also tend to smoke less, exercise more and pay more attention to supplements, so it’s hard to credit the diet alone. Cognition was not the study’s focus.

Soy and the brain

Soy is a staple for many vegans and one of the best plant sources of complete protein, choline and isoflavones, plant compounds that act a little like estrogen.

The evidence on soy and thinking is mixed. A meta-analysis of 10 randomized trials in 1,024 postmenopausal women (Cheng 2015) found a small improvement in summary cognitive scores and visual memory with isoflavone supplements. But in a cross-sectional study of 719 older Indonesians (Hogervorst 2008), high tofu intake was linked to worse memory, in line with an earlier finding from the Honolulu-Asia Aging Study. Tempeh was linked to better memory; the authors suggested its higher folate from fermentation might explain this.

On balance, moderate soy intake (2-3 servings a day of whole soy foods such as tofu, tempeh, edamame and soy milk) appears safe and adds choline and protein. The cognitive evidence is limited and mixed.

Frequently asked questions

Is a vegan diet better for the brain than eating meat?

The evidence doesn’t support a blanket claim either way. A well-planned vegan diet is rich in foods linked to lower inflammation and better heart health. A well-planned omnivorous diet with fatty fish, eggs and plenty of vegetables provides those foods plus DHA, B12, choline and creatine without supplements. The worst option is any diet dominated by ultra-processed food.

How long does B12 deficiency take to cause symptoms?

The body stores several years’ worth of B12, mostly in the liver, so symptoms usually develop gradually over years. That means many vegans feel fine while their stores run down. Some people develop raised homocysteine and subtle cognitive changes before deficiency is diagnosed. That’s why you need a reliable B12 source from the start, not after symptoms appear.

Do vegans have a higher risk of dementia?

There is no strong evidence that vegans as a group have higher dementia rates. The large cohorts haven’t reported dementia by vegan status with enough power to tell. The concern is specific deficiencies, especially B12 and DHA, that are risk factors for cognitive decline. Whether a well-supplemented vegan has the same risk as an omnivore on a high-quality diet hasn’t been studied.

Sources

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