Many nutrients really are “food for thought.” The brain is the most active part of the body and has an enormous appetite, requiring about 20 percent of our total energy intake to function (1). But energy is not the sole source of “food” for the brain: vitamins, fatty acids and minerals are also important for optimizing cognitive health. The high energy demands and the considerable blood flow to the brain mean that nutrients involved in energy metabolism and producing healthy blood cells will help us maintain normal cognition, such as the B-vitamins and iron (2). Other micronutrients play an unappreciated role in brain health: omega-3s, vitamin E and vitamin D. How do they contribute to nutrition for the brain?
Long-chain omega-3 polyunsaturated fatty acids
Also called “omega-3s”, the long-chain omega-3 polyunsaturated fatty acids EPA and DHA play a vital role in brain health. Omega-3s are present in all cell membranes and are major structural fats in the brain, with DHA representing about 97% of all the omega-3 fatty acids found there (3). The evolution of the human brain may actually be linked to omega-3s, where the larger brain of modern humans occurred at a time in pre-history when seafood was first widely included in the diet (4). EPA and DHA molecules are deeply curved due to their unsaturated bonds, which means that they are flexible within the membranes. They help improve the flow of molecules across cell membranes, and therefore the transfer of information inside and outside the cell (5), particularly brain cells (4). The flow of molecules through brain cells is important for cognitive performance and normal brain activity (6), as well as contributing to flows of molecules through the membrane. EPA and DHA are important for the maintenance of brain cells and their complex network within the nervous system and appear to play a role in brain plasticity (6). Laboratory studies show that EPA and DHA also have anti-inflammatory properties, suggesting a role in supporting the aging brain (7).
Omega-3s have been tested in clinical trials across the lifespan to evaluate their effects on a range of measures of brain development and performance (8). Studies conducted during pregnancy (9, 10), infancy and childhood, times of rapid brain growth demonstrate the importance of DHA and it is now recognized to be a key nutrient in the health of the brain and in normal brain development and function (11).
Vitamin E is best known for its antioxidant ability. In nature, vitamin E is found in many types of foods with high oil content, such as nuts, where it prevents the oils from becoming rancid. In the body, it has a similar role of protecting fats (including omega-3s) from oxidative stress (12, 13). For example, when vitamin E levels are low, red blood cells are more likely to burst due to damage to the fats within the cells, and this is the basis of vitamin E recommendations (14). It is this antioxidant activity that has also stimulated interest in the neuroprotective potential of vitamin E.
Before birth, vitamin E can affect biological processes related to normal brain development (13). Preterm infants are born before the main transfer of fat-soluble compounds such as vitamin E occurs (15). Vitamin E levels are low in preterm infants, and correcting this deficiency can not only help reduce the risk of bleeding in the brain, plus help the eye to develop normally (15, 16).
In adults, vitamin E may help the brain to maintain its ability to change throughout life (13). In particular, by reducing the amount of oxidative stress in the brain, it seems that vitamin E can help maintain cognition and brain plasticity (13), which could be the reason why higher vitamin E intakes appear to support cognition in older people (17). An example is from a large study conducted in 2,613 people residing in the Netherlands. People with the lowest intakes of vitamin E had twice the decline in memory measured over five years than people with higher intakes (18).
While vitamin D is more well-known for its role in bone health, studies suggest that it may also contribute to cognition (19). It seems that brain tissue can react to levels of vitamin D in the blood, and the enzyme responsible for converting the storage form of vitamin D to the active form is also present in the brain (20).
In the developing brain, deficiency in vitamin D affects the size of various sections in the brain. Evidence from animal studies show that the brain’s neocortex, which is responsible for complex brain functions such as language and cognitive ability, is proportionately thinner in offspring when pregnant mothers are vitamin D deficient (21). Some studies in humans have found that vitamin D deficiency in mothers increases the risk of poorer developmental outcomes in children (21). For example, mental and psychomotor skills were higher in children of mothers with an adequate vitamin D status (22), and children of women with low vitamin D levels at 16 weeks’ gestation had a greater risk of language impairment after adjustment for a range of confounding variables (23). The timing of deficiency may affect cognitive development, as there are certain critical time periods during gestation in which the brain undergoes specific changes that can be affected by vitamin D deficiency (21).
In adults, some observational evidence links lower vitamin D levels in winter with poorer mental performance, particularly working memory and the ability to make complex decisions (24). Very high circulating vitamin D levels, which can be obtained with sun exposure or dietary supplements, were associated in better verbal fluency in adults (25). In a supplementation study, verbal memory was improved when adults took a high dose vitamin D supplement (4000 IU per day), compared to a low dose supplement (400 IU per day), especially in people deficient at baseline (26).