Natural killer cell activity in elderly men is enhanced by beta-carotene supplementation

Abstract

Natural killer (NK) cell activity has been postulated to be an immunologic link between beta-carotene and cancer prevention. In a cross-sectional, placebo-controlled, double-blind study we examined the effect of 10-12 y of beta-carotene supplementation (50 mg on alternate days) on NK cell activity in 59 (38 middle-aged men, 51-64 y; 21 elderly men, 65-86 y) Boston area participants in the Physicians' Health Study. No significant difference was seen in NK cell activity due to beta-carotene supplementation in the middle-aged group. The elderly men had significantly lower NK cell activity than the middle-aged men; however, there was no age-associated difference in NK cell activity in men supplemented with beta-carotene. beta-carotene-supplemented elderly men had significantly greater NK cell activity than elderly men receiving placebo. The reason for this is unknown; however, it was not due to an increase in the percentage of NK cells, nor to an increase in interleukin 2 (IL-2) receptor expression, nor to IL-2 production. beta-carotene may be acting directly on one or more of the lytic stages of NK cell cytotoxicity, or on NK cell activity-enhancing cytokines other than IL-2, such as IL-12. Our results show that long-term beta-carotene supplementation enhances NK cell activity in elderly men, which may be beneficial for viral and tumoral surveillance.

Enhancing immunity by dietary consumption of a probiotic lactic acid bacterium (Bifidobacterium lactis HN019): optimization and definition of cellular immune responses

“…Immune enhancement by B. lactis B-L Chiang et al are important indices of innate (`natural') immunity, and are commonly employed to gauge the capacity of dietary interventions to stimulate the immune system (Schiffrin et al, 1995;Santos et al, 1996). The present observations con®rm results from a previous clinical trial, which had demonstrated enhanced peripheral blood cell phagocytic activity and production of the cytokine interferon-alpha among elderly subjects (aged 60 ± 83 y) following consumption of B. lactis (Arunachalam et al, 2000).…”

Low-dose supplementation with lycopene or β-carotene does not enhance cell-mediated immunity in healthy free-living elderly humans

“…An increase in the percentage NK cells was reported in a non-controlled trial of men aged 35 ± 79 with either oral leukoplakia or Barrets oesophagus, who were supplemented with 30 mg b-carotene daily for 3 months . In contrast, several controlled studies in healthy young or elderly volunteers have reported no effect of supplementation with b-carotene (Ringer et al, 1991;van Poppel et al, 1993;Daudu et al, 1994;Santos et al, 1996), or indeed vitamin E (Meydani et al, 1995), on lymphocyte subsets. The results from the studies of disease groups should be interpreted with care, bearing in mind the dif®culty in controlling these trials adequately.…”

“…Several studies have shown that the immune response of healthy elderly volunteers is also enhanced by supplements containing dietary antioxidants (Meydani et al, 1990;Chandra, 1992;Santos et al, 1996).…”

The prevalence and risk factors for age-related macular degeneration in rural–urban India, Sankara Nethralaya Rural–Urban Age-related Macular degeneration study, Report No. 1

“…Santos et al (127) showed that neither short-term, high-dose (90 mg/day for 3 weeks) nor long-term, moderate-dose (50 mg every 2 days for 12 years) supplementation with β-carotene had a significant effect on in vitro or in vivo indices of T cell-mediated function. However, longterm β-carotene supplementation did increase natural killer cell activity in older people (128).…”