Concentration of dietary N-6 polyunsaturated fatty acids and the human immune status

We examined the effect of the dietary concentration of total fat and n-6 polyunsaturated fatty acids (PUFA) on the immune status of seven healthy women (age 30-65 years) who lived at our metabolic suite. During the first 20 days all subjects consumed a stabilization diet that contained 5.2 energy percent (en%) PUFA and 41.1 en% fat. For the next 40 days, three subjects consumed a diet with 3.2 en% PUFA and 26.1 en% fat, while the remaining four subjects consumed a diet with 9.1 en% PUFA and 31.1 en% fat. For the next 40 days, the diets of the two groups were crossed over. Blastogenesis of peripheral blood mononuclear cells cultured with phytohemagglutinin, concanavalin A, protein A, and pokeweed, and the serum concentrations of complement fractions C3 and C4 were significantly increased upon the feeding of both low fat (26.1 or 31.1 en%) diets compared to the values when the high fat (41.1 en%) diet was fed. None of the indices tested were different when the high PUFA (9.1 en%) and low PUFA (3.1 en%) diets were compared. Our results indicate that low fat diets improve some of the indices of human immune status and that a moderate increase in the level of n-6 PUFA in an otherwise low fat diet does not suppress the human immune system.