Diet plays a crucial role in brain structure, function, and our overall brain health. From physically becoming our brain cells to altering neurotransmitters, brain immunity, metabolism, and neuroplasticity, every bite of food can be a vote for or against our current and future brain wellness. But diet conversations are also fraught with sensationalism, conflicts of interest, and unhelpful complexity. In this post, we explore four of the most popular eating patterns—vegan, ketogenic, carnivore and Mediterranean—and evaluate what the data really tells us about their effects on brain health.
1. The Vegan Diet
A vegan diet eliminates all animal products, focusing instead on plant foods that include fruits, vegetables, grains, nuts, and seeds. Like many diets, veganism has a vocal following who advocate for its compelling benefits to human health. Vegans will also often emphasize the benefit to animal welfare that can be an added (or central) value proposition to this dietary pattern. One benefit to veganism is a high intake of polyphenols—potent antioxidants linked in multiple studies to lower rates of cognitive decline—and soluble fiber that feeds gut microbes, promoting a diverse microbiome, and is independently associated with better brain health.
A vegan diet may lower systemic inflammation, a known driver of brain issues. Yet strict vegans may be at risk for insufficient intake of EPA and DHA (the brain’s key omega-3 fatty acids) and critical brain vitamins like B12 and D. While some tout concerns for phytates and lectins in some grains and legumes due to their potential to impair nutrient absorption, the “anti-nutrient” concern is often overstated. A bigger concern is ultra-processed vegan junk food—meat substitutes, sugary snacks and refined oils—that aren’t doing anyone’s brain health any favors. A thoughtful vegan diet centered on whole foods can be a great vote for brain health, but it demands attention to nutrient gaps and consideration for supplementation and nutrient testing.
2. The Ketogenic Diet
The ketogenic diet (aka “keto”), so named for its ability to produce “ketone bodies” that can act as alternative fuel for the brain, drastically reduces carbohydrates—typically to 5–10% of daily calories—while increasing fat consumption. A keto diet has been used as therapy for drug-resistant epilepsy since the 1920’s with evidence showing ketones may help stabilize neuronal excitability and reduce seizure frequency in adults and children. Early data suggests potential for mild cognitive improvements in early Alzheimer’s patients, possibly by bypassing impaired glucose use in in the brain. Keto is also proven to excel at improving systemic metabolic health, with targeted effects on insulin sensitivity and reversing type 2 diabetes markers. With this said, a keto diet is often low in fiber and polyphenols—leading to constipation and microbiome alterations. Saturated fat intake typically rises as well, risking the potential for unfavorable cholesterol changes in certain people unless care is taken to increase monounsaturated and polyunsaturated fats found in olive oil, nuts, and fatty fish. Finally, adherence to keto can present long term challenges, and some now recommend cyclic keto to offset some of these risks.
3. The Carnivore Diet
At the extreme end of low-carb dieting is the carnivore diet of social media fame. The diet consists of zero plant foods, instead allowing only meat, fish, eggs and select dairy. Some clear benefits of a minimally-processed animal based diet can include reductions in ultra-processed foods and added sugars. Anecdotal reports often highlight value to autoimmune and metabolic symptoms. Yet, as of 2025, no human trials have assessed the long-term cognitive or neuroprotective outcomes of the carnivore diet. Like the keto diet (but potentially to a larger extent), a carnivore diet excludes fiber and polyphenols, while high saturated fat and red meat consumption raise additional concerns. Sustainability and price are additional concerns.
4. The Mediterranean Diet
The Mediterranean diet, simply put, is the best-studied diet for benefitting multiple aspects of brain health. While variably defined, its emphasis is on minimally processed foods rich in healthy fats, proteins, fiber and plants, and minerals like vitamin D, Vitamin C, and vitamin E. In practice, this means more vegetables, fruits, fish, olive oil, as well as some whole grains and poultry, and an allowance for a bit of wine. Consuming this diet is linked to benefits that extend from mood disorders to Alzheimer’s prevention to better brain metabolism to stroke prevention. It’s been shown to decrease inflammation, improve vascular health, and help and foster a healthy gut-brain connection. Unlike more restrictive diets, the Mediterranean diet allows for flexibility in its components. While some variants of the diet can get pricey, this diet nevertheless remains the best bet for most people when it comes to protecting and boosting brain function.