Effects of a nutritional supplement on the immune response and cytokine production in free-living Chilean elderly.

Background: Immune response is impaired in the elderly. Our aim was to study the effects of a special nutritional formula on the immune response and response to influenza and pneumococcal vaccination in elderly subjects.

Methods: Sixty healthy subjects aged > or = 70 years, with a Mini Mental score > or = 22 were studied. Half of the subjects received a special nutritional formula (in addition to the regular diet) providing, among other nutrients, 480 kcal, 31 g proteins, 120 IU vitamin E, 3.8 microg vitamin B12, 400 microg folic acid, 10(9) cfu Lactobacillus paracasei (NCC 2461), and 6 g of fructo-oligosaccharides. At 4 months of follow-up, subjects were vaccinated against influenza and pneumococcus. Lymphokine production by mononuclear cells (PBMC), lymphocyte subpopulations, and natural killer cell (NK) activity were measured at baseline and 4 months of follow-up (before vaccination). Antibodies against influenza and pneumococcal antigens and flu-stimulated production of interferon gamma and interleukin-2 by PBMC were measured at 4 and 6 months. Skin response to 7 recall antigens and body composition were assessed at baseline and at 4 and 12 months. All infections occurring during the study period were recorded.

Results: NK activity increased in supplemented subjects and decreased in nonsupplemented individuals. Interleukin-2 production by PBMC and the proportion of T cells with NK activity decreased in controls and did not change in supplemented subjects. Supplemented subjects reported less infections than nonsupplemented individuals (in 13% and 22% of scheduled visits, respectively; p = .02).

Conclusions: This nutritional supplement increased innate immunity and protection against infections in elderly people.