Veganuary, a movement encouraging people to adopt a vegan diet for the month of January is the thing to do in January.
It has surged in popularity as a response to ethical, environmental, and health concerns and for many people it’s a short term change but others keep it up long term. So what happens to brain health when people suddenly remove all animal products from their diets? Is a vegan diet supportive of brain function, or could it inadvertently harm cognitive health?
To answer this question, we need to evaluate Veganuary in light of what we know about optimum nutrition for the brain—particularly the vital role of omega-3 fatty acids, B vitamins, and other essential nutrients.
We often forget that the brain, as explained in Upgrade Your Brain, is fundamentally a product of what we feed it.
Modern science leaves little doubt that nutrients such as omega-3 DHA, B12, and choline are non-negotiable for optimal brain health. Removing key sources of these nutrients—as a vegan diet often does—without proper supplementation can risk brain function, memory, and even long-term cognitive integrity.
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The brain is 60% fat, and omega-3 fatty acids, particularly DHA (docosahexaenoic acid), are critical for its structure and function. DHA makes up the bulk of neuronal membranes, enabling communication between brain cells, memory retention, and overall cognitive performance [1]. Research consistently shows that DHA deficiency correlates with reduced cognitive ability, mood disorders, and increased risk of neurodegeneration [2].
Animal foods, particularly oily fish, are the richest sources of preformed DHA. On a vegan diet, the main plant-based source of omega-3 comes in the form of ALA (alpha-linolenic acid), found in flaxseeds, walnuts, and chia seeds. However, the conversion of ALA to DHA in the human body is remarkably inefficient—typically less than 5% [3]. Without preformed DHA from marine sources or supplementation with algae-derived DHA, vegans are likely to fall short of their brain’s DHA needs.
Studies reveal that populations consuming more fish, such as the Japanese, have far lower incidences of dementia and mental decline compared to Western nations, where fish intake is minimal. A meta-analysis confirmed that higher omega-3 levels correlate with a lower risk of cognitive decline [4]. For individuals adopting a vegan diet without supplementing DHA, there’s a real risk of impairing brain function over time.
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Vitamin B12 is another nutrient that becomes a potential red flag during Veganuary. B12, found almost exclusively in animal products such as meat, fish, and dairy, plays a crucial role in maintaining brain function, energy metabolism, and protecting against neurological damage. It is essential for methylation, a process that keeps homocysteine levels in check. Elevated homocysteine has been shown to shrink brain volume and accelerate cognitive decline [5].
A lack of B12 results in pernicious anemia, brain fog, memory loss, depression, and even irreversible nerve damage. Worryingly, B12 deficiency is common among vegans who do not supplement or consume fortified foods. Even those who attempt to rely on plant-based sources of B12, such as spirulina or fermented foods, are often misled—these contain inactive analogues of B12 that are not bioavailable to humans [6].
For Veganuary participants, the failure to address B12 through supplementation could lead to symptoms of mental fatigue, reduced concentration, and mood imbalances in the short term, while increasing the risk of dementia in the long run.
(This is why we offer our DRIfT 5-in-1 at-home blood test, so you can easily check your omega-3, homocysteine, vitamin D, HbA1C, and glutathione levels from the comfort of your own home while contributing to our research and charitable work).
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Choline, an often-overlooked nutrient, is another brain-essential compound predominantly found in animal foods like eggs, liver, and fish. It is the precursor to acetylcholine—a neurotransmitter essential for memory, learning, and mental clarity. Without adequate choline, cognitive performance can take a significant hit, especially in the aging brain [7].
Eggs, for example, are one of the richest sources of dietary choline. However, for individuals participating in Veganuary, eggs are off the table. While small amounts of choline can be found in soybeans, quinoa, and cruciferous vegetables, meeting the brain’s daily requirements is nearly impossible without animal foods or supplementation. Emerging research suggests that a low choline intake may even contribute to neuroinflammation and a higher risk of Alzheimer’s [8].
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Vitamin D, a hormone as much as a vitamin, is vital for mental health, cognition, and neuroprotection. Deficiency in vitamin D has been linked to depression, brain aging, and increased dementia risk. During winter, when Veganuary occurs, obtaining sufficient vitamin D is already challenging for most individuals living in northern latitudes.
While vitamin D can be found in small amounts in mushrooms exposed to UV light, it is primarily found in oily fish, egg yolks and fortified dairy—all of which are absent in a vegan diet. If Veganuary participants fail to supplement with vitamin D3, they risk worsening mood, memory, and overall mental resilience during the winter months [9].
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Beyond omega-3, B12, and choline, a vegan diet also increases the risk of deficiencies in iron, zinc, and high-quality protein—all critical for brain health. Heme iron, found in meat, is far more bioavailable than non-heme iron from plants. Iron deficiency is associated with brain fatigue, poor concentration, and low mood [10]. Similarly, zinc, which is vital for neurotransmitter function and neural repair, is far less bioavailable in plant foods due to anti-nutrients like phytates.
Protein is equally important for maintaining neurotransmitter balance and brain structure. While it is possible to obtain sufficient protein on a vegan diet, doing so requires meticulous planning. Without adequate protein, mood and energy levels can decline rapidly.
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While the standard Veganuary approach—removing animal products without careful planning—poses clear risks to brain health, a well-supplemented vegan diet can be brain-friendly. This requires regular testing (like the DRIfT test) and then personalised and conscious supplementation of algae-derived DHA, vitamin B12, vitamin D3, choline, and possibly zinc and iron, based on an individual’s test results.
To make Veganuary work without compromising cognitive health, I recommend the following:
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While Veganuary can be a noble effort for ethical and environmental reasons, it requires careful consideration of brain health.
Without key nutrients like DHA, B12, and choline, individuals risk compromising their mental energy, memory, and mood. Nutrition is not just about ethics; it’s about feeding the brain the essential building blocks it needs to thrive.
A brain-friendly diet—whether vegan, pescatarian, or omnivorous—prioritises optimum nutrition to enhance cognitive performance, mental well-being, and longevity. If you are choosing Veganuary, do it mindfully, supplementing intelligently to protect and upgrade your brain.
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Food for the Brain is a not-for-profit educational and research charity that offers a free Cognitive Function Test and assesses your Dementia Risk Index to be able to advise you on how to dementia-proof your diet and lifestyle.
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