Does a Plant-Based Diet Affect Mental Health?

Plant-based diets lack vitamin B12 and may also make other key nutrients harder to absorb. Learn how to compensate.

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Switching to a plant-based diet may feel like a step toward better health or a kinder world, but is it gentler on your mental well-being?

When occupational therapist Megan Bezuidenhout switched to a vegan diet, she expected to feel healthier. But after just a few months, chronic anxiety and low mood left her questioning whether her new eating habits were affecting her brain.

As plant-based diets gain popularity, more research has linked them to nutrient deficiencies critical for brain health. Without careful meal planning, a plant-based diet can lead to deficiencies with serious consequences for both physical and mental health.

Mental Health Risks

Many studies suggest a strong link between avoiding meat and an increased risk of mental health disorders.

A 2020 study published in Critical Reviews in Food Science and Nutrition found that people who avoid meat experience significantly higher rates of anxiety and depression. In another study, more than 28 percent of meat abstainers had symptoms of depression, compared with a little more than 16 percent of meat eaters. Similarly, in another study, lifetime anxiety rates were as high as 31.5 percent among meat abstainers, compared with 18.4 percent among meat eaters.

Nutritional Gaps in Plant-Based Diets

Plant-based diets, especially vegan ones, often fail to provide key nutrients in bioavailable forms—nutrients the body can easily absorb and use. According to Dr. Georgia Ede, a Harvard-trained psychiatrist specializing in nutritional and metabolic psychiatry, nondairy animal foods such as meat, seafood, and poultry uniquely supply every essential nutrient in forms that the body readily absorbs.

A systematic review of dozens of nutrient measurement studies found that vegans are more likely to be deficient in vitamin B12, vitamin D, zinc, iodine, and omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—all of which are essential to brain health.

“The brain requires every essential nutrient to function properly, so if you have a deficiency in any of these nutrients, your mental health could suffer,” Ede said.

She pointed out that nutrient deficiencies in vegan diets extend beyond just vitamin B12 deficiency, a common concern for plant-based eaters.

While some foods contain essential nutrients, Ede explained that the body doesn’t always absorb them efficiently.

“Just because a plant food contains a nutrient doesn’t mean you can access it,” she said, adding that compounds in plants (antinutrients) can interfere with absorption, making it harder to obtain key vitamins and minerals from plant-based sources alone.

Missing Nutrients and Their Effect on Mental Health

Here’s how key nutrient deficiencies in plant-based diets can affect mental health.

Iron

Iron in plant-based sources exists as nonheme iron, which, according to a 2024 study, has an absorption rate of only 2 percent to 20 percent. In comparison, heme iron from animal sources is absorbed at a significantly higher rate of 15 percent to 35 percent.

Because iron deficiency plays a critical role in brain function, inadequate intake or poor absorption may contribute to conditions such as attention-deficit/hyperactivity disorder (ADHD) and other psychiatric disorders.

Zinc

Zinc from plant sources, such as legumes and whole grains, is often poorly absorbed because of phytates that bind to it, Mpho Tshukudu, an integrative and functional nutritionist, told The Epoch Times.

Zinc deficiencies are associated with ADHD, major depression, and psychotic symptoms.

Omega-3 Fatty Acids

About 20 percent of the brain comprises DHA, an essential component for brain health, primarily found in animal foods. However, plant-based omega-3 sources such as flax and chia seeds contain alpha-linolenic acid (ALA), which has a limited conversion rate to DHA of only 2 percent to 15 percent, Ede said.

Therefore, it’s not surprising that DHA levels are 31 percent lower in vegetarians and 59 percent lower in vegans compared with meat eaters.

Insufficient DHA intake has been linked to a higher risk of suicide and conditions such as autism, depression, schizophrenia, and dementia.

Mental illness is multifactorial, and while nutrients such as DHA may play a role, they are just one piece of the puzzle.

The table below highlights key nutrients found in plant-based foods and the challenges associated with their absorption.

The Epoch Times

Managing Nutritional Needs

Despite these challenges, it is possible to meet nutritional needs on a plant-based diet with careful planning. Tshukudu shared the following considerations:

• Pair plant-based iron sources (e.g., lentils and spinach) with vitamin C-rich foods such as citrus fruits, peppers, and tomatoes to boost iron absorption.
• Use techniques such as soaking, fermentation, and sprouting to lower phytate levels and improve the absorption of zinc, iron, magnesium, and calcium.
• Consider microalgae-based supplements for EPA and DHA, especially during pregnancy or adolescence, when nutritional demands are higher.
• Optimize nutrient conversion by eating adequate protein, vitamins, and minerals to support metabolic functions.
• Avoid trans fats and alcohol, which interfere with nutrient absorption and metabolism by promoting inflammation.
• Monitor liver function, as it plays a key role in converting certain nutrients, such as in ALA-to-DHA conversion.

Testing for Nutrient Deficiencies

Besides mental health concerns, symptoms such as brittle nails, thinning hair, and dry, irritated skin may signal zinc or essential fatty acid deficiencies.

Consider having blood tests done to detect common deficiencies and ensure adequate nutrition. Consult a health care provider or nutritionist to address gaps with dietary adjustments or supplements.

Bezuidenhout learned firsthand that removing animal products left a gap in her nutritional needs.

“I needed to be intentional about providing my brain with the nutrients it required and plan my meals more carefully,” she said.