|Han, Sung Nim|
Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2012
Publication Date: 12/1/2012
Citation: Han, S., Lichtenstein, A.H., Ausman, L.M., Meydani, S.N. 2012. Novel soybean oils differing in fatty acid composition alter immune functions of moderately hypercholesterolemic older adults. Journal of Nutrition. 142:2182-2187. Interpretive Summary: Given that both advancing age and elevated cholesterol levels are associated with a weakened immune response and increased chances of becoming infected when exposed to infectious microorganisms, it is important to identify factors that contribute to altering immune function. The relative abundance of n-6 and n-3 fatty acids in plant oils has been suggested to impact the immune response. In this study, older adults with higher than normal cholesterol levels were fed diets with different ratios of n-6 to n-3 fatty acids using soybean oils, which contained different levels of these fatty acids and which were assessed for their impact on immune response. The n-6 to n-3 ratio significantly affected the function of immune cells from older adults as measured by their ability to expand their numbers in response to stimuli similar to infectious agents. We found that when consumption of n-6 fatty acid relative to n-3 fatty acid (above 8.7:1) increased, the capability of immune cells to expand decreased. The results from this study indicate that the ratio of n-6 to n-3 fatty acid in the diet has a significant impact on immune response. Thus, nutritionists need to work closely with plant physiologists/geneticists to produce plant oils that will provide the best possible immune response.
Technical Abstract: Linoleic acid (LA) and alpha-linolenic acid (ALA) are essential fatty acids, which play an important role in modulation of T cell proliferation. The effects of feeding novel soybean oils differing in LA/ALA ratios was assessed on T cell proliferation and inflammatory responses of older adults. Eighteen subjects (greater than 50 years old) with elevated cholesterol levels (3.37-4.14 mmol/L LDL cholesterol) consumed five experimental diets in random order for periods of 35 days. Each diet contained 30 percent of energy as fat; 2/3 either high oleic acid soybean oil (HiOleic-SO), soybean oil (SO), low saturated fatty acid soybean oil (LoSFA-SO), hydrogenated soybean oil (Hydrog-SO), or low alpha-linolenic acid soybean oil (LoALA-SO) resulting in LA/ALA ratios of 2.98, 8.70, 9.69, 15.22, 18.31, respectively. Subjects exhibited significantly higher proliferative response to PHA compared to their baseline following consumption of SO diet (25.5 percent, p equals 0.012), LoSFA-SO diet (21.3 percent, p equals .035), or HiOleic-SO diet (22.7 percent, p equals 0.025). Proliferative response was similar to the baseline after subjects consumed diets with LA/ALA ratio greater than 10 (Hydrog-SO and LoALA-SO). Post diet intervention, LA/ALA ratio were significantly correlated with proliferative responses to PHA. Optimal proliferative response was observed at LA/ALA ratio of 8.70, with inverse correlation between proliferative response and ratios of LA/ALA above that ratio. These effects were independent of changes in prostaglandin E2 production, inflammatory cytokines, or cytokines involved in growth of lymphocytes. These data suggest that LA/ALA ratio modulates proliferative ability of T lymphocytes, which may be due to subtle changes in fatty acid compositions of the phospholipid of immune cells.