The L.A. Times reports today the neg­a­tive results of the lat­est ran­dom­ized trial test­ing the effects of DHA sup­ple­ments on Alzheimer’s symp­toms (DHA is an omega-3 fatty acid).

The study … exam­ined 402 peo­ple with mild to mod­er­ate Alzheimer’s. They were ran­domly assigned to take 2 grams a day of omega-3 cap­sules con­tain­ing docosa­hexaenoic acid (or DHA) or a placebo cap­sule. The par­tic­i­pants were fol­lowed for 18 months, and their cog­ni­tive and func­tional abil­i­ties were reassessed. They also under­went MRI to look at the brain.

There was no ben­e­fit seen in the patients tak­ing omega-3 fatty-acid sup­ple­ments in either brain vol­ume or cog­ni­tive function.

Com­ments: Does this study mean that DHA or omega-3 in gen­eral are not good for the brain? No! This study sug­gests that tak­ing DHA sup­ple­ments after Alzheimer’s diag­no­sis is not help­ful. Prior evi­dence shows that omega-3 con­sump­tion (espe­cially DHA) long before the onset of Alzheimer’s symp­toms reduces the risk of devel­op­ing the dis­ease. Indeed, sev­eral stud­ies have shown that eat­ing fish (the pri­mary source in our diet of omega-3 fatty acids) is asso­ci­ated with a reduced risk of cog­ni­tive decline or dementia.

The authors of the JAMA study also spec­u­late that DHA sup­ple­ments could be used as a treat­ment for peo­ple who have not yet been diag­nosed with Alzheimer’s but are already devel­op­ing demen­tia pathol­ogy in their brain: “Indi­vid­u­als inter­me­di­ate between healthy aging and demen­tia, such as those with mild cog­ni­tive impair­ment, might derive ben­e­fit from DHA sup­ple­men­ta­tion, although fur­ther study will be nec­es­sary to test this hypoth­e­sis.” 

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 Read the rest of this entry »