Dietary alpha-linolenic acid and immunocompetence in humans.

We examined the effect of dietary alpha-linolenic acid (ALA) on the indices of immunocompetence in 10 healthy free-living men (age 21-37 y) who consumed all meals at the Western Human Nutrition Research Center for 126 d. There was a stabilization period of 14 d at the start when all 10 subjects consumed basal diet (BD) and there were two intervention periods of 56 d each. Five of the subjects consumed the basal diet and the other five consumed flax-seed-oil diet (FD) during each intervention period. Feeding of FD suppressed the proliferation of peripheral blood mononuclear cells when they were cultured with phytohemagglutinin-P (P = 0.041) and concanavalin A (P = 0.054) and the delayed hypersensitivity response to seven recall antigens (NS). Concentrations of immunoglobulins in serum, C3, C4, salivary IgA, the numbers of helper cells, suppressor cells, and total T and B cells in the peripheral blood were not affected by the diets.