A for Immunity

February 25/Biotech Law Weekly -- According to recent research published in the Journal of Nutrition, "Recommendations for vitamin A intake and liver stores are based on maintaining normal vision. We propose that higher levels may be required to maintain normal innate immune function."

"To test this hypothesis, we conducted an eight-wk residential study among 36 healthy Bangladeshi men with low vitamin A stores. Subjects were randomized to receive vitamin A (240mg in 4 doses) or placebo during study weeks two and three. They received two vaccines during week five, and vitamin A stores were estimated by isotopic dilution at week eight. The serum concentration of the chemokine interferon-gamma-induced protein 10, a component of T-helper 1 (Th1) response, increased significantly after supplementation and was positively and significantly associated with vitamin A stores.

Blood concentrations of natural killer (NK) and NK T-cells, which have anticancer and antiviral activity, were positively associated with stores (P<0,05), as was monocyte oxidative burst (P<0.05), a marker of bacterial killing ability. However, serum interleukin (IL)-6 and IL-17, cytokines that regulate the antibacterial Th17 response, were significantly and negatively associated with stores, as was production of the regulatory cytokine IL-10 by whole-blood cultures stimulated with bacterial lipopolysaccharide. In summary, vitamin A stores were positively associated with several measures of innate immune activity across a broad range of stores, suggesting that vitamin A enhances protection against diverse pathogens even at concentrations above those needed to maintain normal vision," wrote S.M. Ahmad and colleagues, University of California.

The researchers concluded, "The negative association of stores with serum IL-6 and IL-17 suggests that not all protective responses are similarly enhanced by vitamin A. J. Nutr. 139: 377-385, 2009."

Ahmad and colleagues published their study in the Journal of Nutrition ("Markers of Innate Immune Function Are Associated with Vitamin A Stores in Men." Journal of Nutrition, 2009;139(2):377-385).

For additional information, contact C.B. Stephensen, University of California, Dept. of Nutrition, Program International & Community Nutrition, Davis, CA 95616, USA.

From the February 16, 2009, Prepared Foods E-dition