omega-3s

A diet high in omega-3s, the fatty acids found in fatty fish like salmon
as well as walnuts, appears to significantly block the negative effects
of the APOE4 gene -- the "bad" APOE gene found in 50% of all Alzheimer's
patients and in about 15% of the population.

 http://www.naturalnews.com/031499_omega-3s_Alzheimers.html#ixzz1F0I4FMKP