In other words, may some foods be specif­i­cally good for brain function?

For a great in-depth review of the effects of food on the brain you can check out Fer­nando Gomez-Pinilla’s recent arti­cle in Nature Reviews Neu­ro­science (ref­er­ence below). Here is an overview of the state off the research.

Sev­eral com­po­nents of diet seem to have a pos­i­tive effect on brain function.

Omega-3 fatty acids

These acids are nor­mal con­stituents of cell mem­branes and are essen­tial for nor­mal brain func­tion. Omega-3 fatty acids can be found in fish (salmon), kiwi, and wal­nuts. Docosa­hexaenoic acid, or DHA, is the most abun­dant omega-3 fatty acid in cell mem­branes in the brain. The human body pro­duces DHA but not enough. So we are depen­dent on the DHA that we get from what we eat.

A ran­dom­ized double-blind con­trolled trial (which means seri­ously con­ducted sci­en­tific study) is cur­rently look­ing at the effect of tak­ing omega-3 fatty acids on children’s per­for­mance at school in Eng­land. Pre­lim­i­nary results (Port­wood, 2006) sug­gest that the group of chil­dren who received omega-3 fatty acids showed some level of improve­ment in school per­for­mance com­pared to the group of chil­dren who received a placebo. More research is needed to con­firm these results but they look promising.

Fatty acids are also regarded as a promis­ing but untested treat­ment as mood sta­bi­lizer. Hibbeln (1998) showed a neg­a­tive cor­re­la­tion between fish con­sump­tion (i.e., omega-3 fatty acid intake) and major depres­sion in many coun­tries includ­ing the United States, Canada, Ger­many and France. A neg­a­tive cor­re­la­tion means that as con­sump­tion of omega-3 decreases, the preva­lence of major depres­sion increases. Note that a cor­re­la­tion does not imply cau­sa­tion: we can­not con­clude that low omega-3 con­sump­tion causes major depression.

Folic acid (or folate)

Folate is gen­er­ated by the liver, after the intes­tine has absorbed vit­a­min B. It is found in spinach, orange juice and yeast. Ade­quate lev­els of folate are essen­tial for brain function.

Cor­rada and col­leagues (2005) have shown that peo­ple who take more folate than oth­ers have less risks of devel­op­ing Alzheimer’s dis­ease. Note again that this is a cor­re­la­tion so more research is needed to deter­mine whether folate is indeed respon­si­ble for the risk reduction.

Flavonoids

These are found in cocoa, green tea, Ginko biloba tree, cit­rus fruits, wine and dark choco­late. The antiox­i­dant effects of flavonols have been shown in vitro (in the test tube) but more research is needed to estab­lish the effects of flavonols in vivo (in a liv­ing organ­ism). So far, Ginko biloba extracts have been shown to reduce mem­ory impair­ment in mice with mixed effects in humans, at best.

Antiox­i­dant foods

The brain is highly sus­cep­ti­ble to oxida­tive dam­age. This is why antiox­i­dant food has become pop­u­lar for their pos­i­tive effects on brain function.

Antiox­i­dants are found in a vari­ety of food: Alpha lipoic is found in spinach, broc­coli and pota­toes; Vit­a­min E is found in veg­etable oils, nuts, green leafy veg­eta­bles; Cur­cumin is found in the curry spice; Vit­a­min C is found in cit­rus fruit and sev­eral plants and veg­eta­bles. Berries are well known for their antiox­i­dant capac­ity but it is not clear which of their many com­po­nents has an effect on cognition.

Guts and the brain

We have seen that what we eat can affect brain func­tion. Inter­est­ingly, it has also been shown that guts hor­mones them­selves can directly influ­ence brain func­tion. Indeed, sev­eral gut hor­mones such as lep­tin (which sends sig­nals to the brain to reduce appetite), ghre­lin (which acts as an appetite stim­u­lant) or insulin (which is secreted by the antic­i­pa­tion of meals and dur­ing diges­tion) have been found to enhance mem­ory for­ma­tion through their action on the hip­pocam­pus. As you know, the hip­pocam­pus is one of the brain struc­tures cru­cial for spa­tial learn­ing and mem­ory for­ma­tion. These gut hor­mones have an effect on the plas­tic­ity (the abil­ity to change) of the con­nec­tions between neu­rons in the hip­pocam­pus. For instance ghre­lin pro­motes the for­ma­tion of new synapse dur­ing learn­ing. Insulin can enter the brain and inter­act directly with cells in the hippocampus.

Final note of cau­tion

Please note that most of the stud­ies show­ing pos­i­tive effects of all these nutri­ents on the brain have been con­ducted in mice. A few human stud­ies are now pub­lished but more research is clearly needed to estab­lish and under­stand the effects of spe­cific foods on brain function.

Ref­er­ences

- Cor­rada, M., Kawas, C., Hall­frisch, J., Muller, D., & Brook­meyer, R. (2005). Reduced risk of Alzheimer’s dis­ease with high folate intake: The Bal­ti­more Lon­gi­tu­di­nal Study of Aging. Alzheimers & Demen­tia, 1, A4.

- Hibbeln, J. R. (1998). Fish con­sump­tion and major depres­sion. Lancet, 351, 1213.

- Gmez-Pinilla, F. (2008). Brain foods: the effects of nutri­ents on brain func­tion. Nature Reviews Neu­ro­science, 9, 568–578.

- Port­wood, M. M. (2006). The role of dietary fatty acids in chil­drens behav­ior and learn­ing. Nutr. Health, 18, 233–247.

— This arti­cle was writ­ten by Pas­cale Mich­e­lon, Ph. D., for Sharp­Brains. Dr. Mich­e­lon, Copy­right 2008. Dr. Mich­e­lon has a Ph.D. in Cog­ni­tive Psy­chol­ogy and has worked as a Research Sci­en­tist at Wash­ing­ton Uni­ver­sity in Saint Louis, in the Psy­chol­ogy Depart­ment. She con­ducted sev­eral research projects to under­stand how the brain makes use of visual infor­ma­tion and mem­o­rizes facts. She is now an Adjunct Fac­ulty at Wash­ing­ton Uni­ver­sity, and teaches Mem­ory Work­shops in numer­ous retire­ment com­mu­ni­ties in the St Louis area.

More arti­cles on the topic:

- A Multi-Pronged Approach to Brain Health

- Overview of Nutri­tional Sup­ple­ments and Brain Fitness

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