Dietary α-linolenic acid and immunocompetence in humans

January 1, 1991 Human Health and Nutrition Data 0 Comments

Dietary α-linolenic acid and immunocompetence in humans

Year: 1991
Authors: Kelley,D.S. Branch, L.B. Love, J.E. Taylor, P.C. Rivera, Y.M. Iacono, J.M.
Publication Name: Am. J. Clin. Nutr.
Publication Details: Volume 53; Pages 40-46.


We examined the effect of dietary α-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. (Author abstract)
The effects of dietary n-3 (ω-3) polyunsaturated fatty acids (PUFAs) on indices of immune status have yielded conflicting results. The incidence of chemically induced tumors has been shown to be markedly decreased fed fish-oil-based or linseed-oil-based diets in only some studies. Results obtained regarding the effects of dietary n-3 fatty acids on blast transformation in response to mitogens are also conflicting. Blast transformation of splenocytes in response to phytohemagglutinin-P (PHA) and concanavalin A (Con A) was suppressed equally by LA, ALA, or arachidonic acid (20:5n-6, AA). The current study was undertaken to describe the effects of dietary n-3 fatty acids on several in vivo and in vitro indices of immune status in healthy men. The results show that overall the flax diet tended to suppress the cell-mediated immunity without affecting the humoral immunity. The suppressive effect of flax diet on cell-mediated immunity was noted both on the proliferation of PBMNCs cultured with the T-cell mitogens PHA and Con A and the DHS skin response to recall antigens. A lack of a more significant effect of the flax diet on the PBMNC proliferation in response to Con A may have resulted partially from the marked variation in these data. The mechanisms involved in the suppression of T-cell functions by ALA were not examined in this study. It may be mediated through the alteration in lymphocyte membrane fatty acid composition, physical properties of the lipoproteins, or prostaglandin synthesis. The authors concluded that their results show that the diet containing flaxseed oil suppressed some of the indices of cell-mediated immunity without affecting any of the indices of humoral immunity tested. Some indices of cell-mediated immunity were not affected by the flax-seed-oil diet. If such suppressive effects can be attained in individuals with autoimmune diseases or chronic inflammations, such diets may be useful in the management of diseases like arthritis, lupus, and allergies. These hypotheses need to be evaluated further. (Editors comments)

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