The newborn brain may be particularly vulnerable to vitamin C deficiency, which has been found in rodent studies to lead to a marked decrease in the number of brain cells in the hippocampus. Although there is no clear evidence that vitamin C supplements on their own improve memory or brain function in adults, two large studies of older adults have found that taking both vitamin C and vitamin E supplements significantly reduced the risk of Alzheimer's. Other indications suggest the efficacy of these vitamins may depend on whether they are taken in through food or through supplements (food is better), and whether the individual has the "Alzheimer's gene" (better not to).
It's been proposed that vitamin E might help prevent Alzheimer's, because of the role that oxidative stress plays in the development of the disease. Vitamin E is an antioxidant. It has been found in cultured cell studies that vitamin E does help protect against the effects of oxidative stress, and results in significantly fewer neurons dying. At the level of the organism, results are not so clearcut. One study of older adults found those eating the most vitamin E-rich foods had a lower risk of developing Alzheimer's, provided they didn't have the 'Alzheimer's gene'. Supplements did not have the same effect. Another, larger, study found that those with high intakes of vitamins E and C were less likely to develop Alzheimer's, regardless of gene status. This was especially true for smokers.
Research indicates that choline is a crucial ingredient in a pregnant woman's diet, for brain development in the fetus. Among older adults, choline, particularly in conjunction with omega-3 fatty acids and uridine (not available from food), has been found to improve memory in those cognitively impaired. Top sources of choline are eggs, peanuts, and meat. Fish and soy are also good sources. A choline food database is available at: www.nal.usda.gov/fnic/foodcomp
Research with rats indicates that increasing magnesium levels in the brain improves learning and memory, apparently through its effects on synaptic density and plasticity. Unfortunately, traditional supplements have little effect on magnesium levels in the brain, but the researchers developed a new compound that was effective. Magnesium deficits are common in the population of industrialized countries, and increase with age. Good sources of magnesium are dark green leafy vegetables (such as spinach), some nuts (almonds and cashews are particularly good), beans, seeds and whole unrefined grains (especially buckwheat). See here for a list of magnesium-rich foods.
Zinc has been linked to cognitive and motor function in very young children and adults, and one small study has found zinc supplements improved cognition, especially attention, in adolescents, who are particularly at risk of zinc deficiency. Red meats, fish and grains are good sources of zinc.