June 11, 2024
Written by: Catrina Hacker
We are constantly overrun with advice about how to eat, whether through advertisements online, diet books, or social media posts. That can make it hard to distinguish science-backed diet tips from misinformed fad diets. While there is no magic food that can make you smarter, there are many components of a healthy and balanced diet that are necessary to keep you brain healthy. In this post I’ll discuss how the foods we eat influence the brain, some of the nutrients essential for brain health, and the science behind a couple popular diets.
How do the foods we eat get to the brain?
Before we can discuss what foods influence brain health, you might be wondering how the foods we eat get to the brain in the first place. One important function of our digestive system is to break food down into the nutrients that our bodies need to function, like fats, proteins, and vitamins1. There are several nutrients that our bodies can’t make and we must get through diet, called essential nutrients2, which is why it’s important to eat a balanced diet. Once your body has extracted nutrients from the food you’ve eaten, they are transported throughout your body via your blood1. When they arrive in the brain, they support a wide variety of important functions (more on that shortly).
Nutrients that are important for brain health
Here are some (not all) of the nutrients that are important for brain function and where you can get them in your diet.
Fats
Foods that contain them3: fatty fish (e.g., salmon, trout, mackerel), nuts (esp. walnuts), and seeds
Nearly 60% of the brain is made up of fats, several of which are essential nutrients (e.g., omega-3s and omega-6s). Fats in the brain play important roles in brain development, maintaining brain structure, producing messengers for communication between neurons, and aiding the brain’s immune system4. Given their diverse brain functions, it’s no surprise that ensuring you consume enough fats may improve a variety of things like mood and memory5.
Vitamin B12
Foods that contain it6: fish, lean meat, poultry, eggs
Vitamin B12 aids the processes that build, repair, and change DNA to keep your cells functioning7,8. Without enough vitamin B12, patients can experience a number of symptoms including changes in mood, cognitive decline, and weakness, numbness, and pain in the extremities9. Vitamin B12 deficiency in adults has been linked to depression6 and cognitive decline9, and it is thought to play an important role in preventing some neurological disorders like Alzheimer’s9 disease. Vitamin B12 plays an especially important role in brain development, which is why deficiency during pregnancy can lead to a number of birth defects7. Most dietary sources of vitamin B12 come from animal-based products, so vegetarians and vegans can sometimes struggle to maintain healthy levels of vitamin B1210.
Vitamin K
Foods that contain it11: leafy green vegetables (e.g., kale, spinach), vegetable oils, and some fruits (e.g., figs and grapes)
Vitamin K plays several important roles in neuron survival and immune responses in the brain12. While the link between vitamin K and cognition is still being established, several studies have shown that older people with lower levels of vitamin K in their body perform worse on some cognitive tasks, like visual memory, than those with higher levels12. One study even found that higher concentrations of vitamin K in the brain were associated with a decreased chance of having dementia13, and another found that patients with Alzheimer’s who consumed more leafy greens had fewer biological markers of Alzheimer’s14. Unfortunately, many older adults do not eat enough vitamin K. Among older adults who do ingest enough vitamin K, vegetables are the strongest contributors, meaning a small lifestyle change could go a long way15.
Antioxidants
Foods that contain them16: berries, dark chocolate, beans, spices and herbs, coffee and tea
Sometimes, when your cells process oxygen, they produce a type of molecule called a free radical. Free radicals can harm cells, so antioxidants are used to neutralize them and prevent damage. This is especially important in the brain, where a lot of oxygen is processed, so many free radicals are produced17. Some studies have linked consumption of antioxidants to improved memory and executive function18,19, although the science is still mixed on whether they can help prevent chronic diseases20. Antioxidants work particularly well in combination with other vitamins and minerals, so getting them naturally through diet as opposed to using supplements may have more benefits20.
Popular diets and brain health
Now that you know about a few nutrients that are important for brain health, you may be wondering whether popular diets that prioritize these nutrients might be associated with better brain health.
The ketogenic diet
Perhaps no diet has been discussed more in the last few years than the ketogenic, or “keto” diet. People partaking in a ketogenic diet reduce their consumption of carbohydrates and replace them with fats. Given the importance of fats for brain function, several studies have looked at whether adhering to the ketogenic diet improves brain health. One study found that in patients medicated for bipolar disorder or schizophrenia, those that followed the ketogenic diet showed more improvement in their symptoms than those who didn’t21. Diet cannot replace medication, but this suggests that changes in diet can improve the effectiveness of medications. The ketogenic diet can also be helpful for patients, especially children, with epilepsy who are not responding to medication22.
The mediterranean diet
Another popular diet that has been linked to good health outcomes is the mediterranean diet. The mediterranean diet emphasizes eating plant-based foods like vegetables, nuts, and seeds, healthy fats like olive oil and avocado, and whole grains23. There is some evidence that the mediterranean diet is good for brain health, although the results are mixed. Of five studies that examined the impact of the mediterranean diet on cognition in healthy adults, most found none or small improvements in cognition when following the mediterranean diet24. Like the ketogenic diet, it may be more helpful for preventing or slowing disease progression in patients with neurological disorders. One study found that Alzheimer’s patients who adhered to a mediterranean diet had fewer biological markers of the disease in their brains than patients who didn’t14. While its association with brain health is still disputed, the mediterranean diet has many other proven health benefits23 and is recommended by the American Heart Association for heart health25.
The big picture
While there are a lot of great reasons to eat healthy, there is no perfect diet that will magically make you smarter. Failing to maintain healthy levels of essential nutrients can harm brain health, but there isn’t much evidence that higher levels or different combinations of them can make healthy individuals smarter. That being said, some special diets can be helpful in preventing and slowing the progression of certain diseases, such as the ketogenic diet for children with epilepsy. It’s also important to remember that there’s a lot more that goes into health than just diet. For example, lots of research supports the importance of regular exercise in improving the health of your mind and body26,27.
At the end of the day, all you can do is make your best effort to live a healthy lifestyle. It’s also important to remember that there is such thing as too much of a good thing. Taking supplements or probiotics that far exceed the levels of nutrients needed by your body or taking a diet to too much of an extreme can have harmful effects28. Some diets that are helpful for some people can be harmful to others depending on other factors impacting their health. Always consult your doctor before making changes to your diet to be sure you’re getting the balance of nutrients you need.
References
1. Your Digestive System & How it Works – NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works.
2. Human nutrition – Vitamins, Minerals, Proteins | Britannica. https://www.britannica.com/science/human-nutrition/Essential-nutrients.
3. What Are the Best Foods for Brain Health? Scripps Health https://www.scripps.org/news_items/4211-what-are-the-best-foods-for-brain-health (2012).
4. Chang, C.-Y., Ke, D.-S. & Chen, J.-Y. Essential Fatty Acids and Human Brain. 18, (2009).
5. Muth, A.-K. & Park, S. Q. The impact of dietary macronutrient intake on cognitive function and the brain. Clin. Nutr. 40, 3999–4010 (2021).
6. Vitamin B-12 and depression: Are they related? Mayo Clinic https://www.mayoclinic.org/diseases-conditions/depression/expert-answers/vitamin-b12-and-depression/faq-20058077.
7. Finkelstein, J. L., Layden, A. J. & Stover, P. J. Vitamin B-12 and Perinatal Health. Adv. Nutr. 6, 552–563 (2015).
8. Kennedy, D. B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review. Nutrients 8, 68 (2016).
9. Reynolds, E. Vitamin B12, folic acid, and the nervous system. Lancet Neurol. 5, 949–960 (2006).
10. Rathod, R., Kale, A. & Joshi, S. Novel insights into the effect of vitamin B12 and omega-3 fatty acids on brain function. J. Biomed. Sci. 23, 17 (2016).
11. Office of Dietary Supplements – Vitamin K. https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/.
12. Alisi, L. et al. The Relationships Between Vitamin K and Cognition: A Review of Current Evidence. Front. Neurol. 10, 239 (2019).
13. Consumption of Vitamins D and K May Keep Memory Diseases Away | Tellus. https://tellus.ars.usda.gov/stories/articles/consumption-vitamins-d-and-k-may-keep-memory-diseases-away.
14. Agarwal, P. et al. Association of Mediterranean-DASH Intervention for Neurodegenerative Delay and Mediterranean Diets With Alzheimer Disease Pathology. Neurology 100, (2023).
15. Harshman, S. G. et al. Vegetables and Mixed Dishes Are Top Contributors to Phylloquinone Intake in US Adults: Data from the 2011-2012 NHANES. J. Nutr. 147, 1308–1313 (2017).
16. Carlsen, M. H. et al. The total antioxidant content of more than 3100 foods, beverages, spices, herbs and supplements used worldwide. Nutr. J. 9, 3 (2010).
17. Lee, K. H., Cha, M. & Lee, B. H. Neuroprotective Effect of Antioxidants in the Brain. Int. J. Mol. Sci. 21, 7152 (2020).
18. Philip, P. et al. Acute Intake of a Grape and Blueberry Polyphenol-Rich Extract Ameliorates Cognitive Performance in Healthy Young Adults During a Sustained Cognitive Effort. Antioxidants 8, 650 (2019).
19. Carrillo, J. Á., Arcusa, R., Zafrilla, M. P. & Marhuenda, J. Effects of Fruit and Vegetable-Based Nutraceutical on Cognitive Function in a Healthy Population: Placebo-Controlled, Double-Blind, and Randomized Clinical Trial. Antioxidants 10, 116 (2021).
20. Antioxidants. The Nutrition Source https://nutritionsource.hsph.harvard.edu/antioxidants/ (2012).
21. Sethi, S. et al. Ketogenic Diet Intervention on Metabolic and Psychiatric Health in Bipolar and Schizophrenia: A Pilot Trial. Psychiatry Res. 335, 115866 (2024).
22. Ketogenic Diet. Epilepsy Foundation https://www.epilepsy.com/treatment/dietary-therapies/ketogenic-diet.
23. What Is the Mediterranean Diet? Cleveland Clinic https://my.clevelandclinic.org/health/articles/16037-mediterranean-diet.
24. Radd-Vagenas, S. et al. Effect of the Mediterranean diet on cognition and brain morphology and function: a systematic review of randomized controlled trials. Am. J. Clin. Nutr. 107, 389–404 (2018).
25. American Heart Association. What is the Mediterranean Diet? http://www.heart.org https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/mediterranean-diet.
26. How Exercise Is Good for Your Brain. Cleveland Clinic https://health.clevelandclinic.org/exercise-and-brain-health.
27. Exercise can boost your memory and thinking skills – Harvard Health. https://www.health.harvard.edu/mind-and-mood/exercise-can-boost-your-memory-and-thinking-skills.
28. Binns, C. W., Lee, M. K. & Lee, A. H. Problems and Prospects: Public Health Regulation of Dietary Supplements. Annu. Rev. Public Health 39, 403–420 (2018).
Cover photo by Mediamodifier from Pixabay
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