Research: FORTES and colleagues,

Listed in Issue 37

Abstract

FORTES and colleagues, National Institute of Health, Rome, Italy studied whether supplemental vitamin A, zinc or both increased immune response in an elderly population .

Background

Methodology

The authors conducted a double-blind, randomised, controlled trial of supplementation with vitamin A and zinc with residents in a public home for older people in Rome, Italy. Of the 178 residents whose health and nutritional status were evaluated initially, 136 residents agreed to participate in the trial. These residents were randomised into 4 treatment groups: Group 1: vitamin A (800 micrograms retinol palmitate); Group 2: zinc (25 mg as zinc sulfate); Group 3: vitamin A and zinc (800 micrograms retinol palmitate and 25 mg as zinc sulfate); Group 4: placebo capsules containing starch. 118 residents completed the trial. Immune tests counts of leukocytes, lymphocytes, T-cell subsets and lymphocyte proliferative response to mitogens were measured prior to and following supplementation.

Results

Zinc increased the number of CD4 + DR + T-cells and cytotoxic T-lymphocytes . People treated with vitamin A had a reduction in the number of CD3 + T-cells and CD4+ T-cells .

Conclusion

The data from this study indicates that zinc supplementation improved cell-mediated immune response; vitamin A had a negative effect upon immune response in this population . Further research is required to clarify the significance of these results.

References

Fortes C et al. The effect of zinc and vitamin A supplementation on immune response in an older population. J Am Geriatr Soc 46(1): 19-26. Jan 1998.

Comment

Although I am not surprised at the positive immune result with zinc, I am surprised that vitamin A negatively affected immune response. The formulations, both of zinc and of vitamin A may not have been optimal; it is generally recognised that an organically chelated zinc formulation orotate or picolinate is superior to a chemically linked group such as sulfate regarding absorption and availability. Further studies ought to be conducted with different formulations of vitamin A before coming to definite conclusions on this subject.

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