β-Carotene and selenium supplementation enhances immune response in aged humans
Steven M. Wood PD, RDa, Carla Beckham BA, BS, SM1, , b, Ayako Yosioka PD2, , b, Hamid Darban PD, CCP3, , b and Ronald R. Watson PD, , b
a Committee of Nutritional Sciences, University of Arizona, Tucson, AZ, USA
b College of Public Health, University of Arizona, Tucson, AZ, USA
Available online 14 September 2000.
Background: Nutritional research has focused on the effects of specific nutrients' ability to cause or prevent cancer. While β-carotene and selenium (both important for antioxidant systems) have cancer prevention capabilities, their antineoplastic mechanism(s) remains to be elucidated. Methods: In a prospective, randomized study design we evaluated immunological changes in free-living, healthy aged humans (57–84 years of age) given a placebo, β-carotene (45 mg/day), and/or selenium (400 μg/day) supplement for 6 months and after 2 months of discontinuation. Peripheral blood lymphocytes were evaluated and subtyped using flowcytometry. Natural killer (NK) cell cytotoxicity was determined by a fluorescent method. Plasma diene conjugates were assessed to evaluate changes in oxidative stress. Results: Selenium and selenium plus β-carotene supplementation caused an increase in total T cells by 27% and 31%, respectively (p < .05). The only group that was different (in T lymphocytes) from the controls (placebo group) after 6 months of supplementation (p < .05) was the selenium-supplemented group (+65%). Much of this increase was the result of an increase in CD4+ T-cell subsets. Selenium or β-carotene supplementation for 3 months increased NK cell cytotoxicity over pretreatment levels by 58% and 34%, respectively; however, these levels returned to +12% and −6% of pretreatment levels after 6 months supplementation. Selenium plus β-carotene supplementation caused an increase in the percentage of NK cell by 121% and 161% at 3 and 6 months, respectively. However, the increased numbers of NK cells were not correlated with NK cell activity. Conclusions: We found that selenium enhanced immune function (NK cell cytotoxicity) and phenotypic expression of T-cell subsets, whereas β-carotene affected only immune function. Increased NK cell cytotoxicity may last for only a short period of supplementation and was not sustained throughout the 6 months of supplementation. Supplemental selenium and β-carotene seemed to affect immune function in aged subjects by different mechanisms.
Author Keywords: β-carotene; selenium; aged; immune function
1 Current address: Biogen Inc., 12 Cambridge Center, Cambridge, MA 02142, USA.
2 Current address: Shokei-Gakuen University, Department of Domestic Sciences, Kumamoto, Japan.
3 Current address: Duquesne University, Department of Clinical Sciences, 125 Health Sciences Building, Pittsburgh, PA 15282, USA.
Address reprint requests to: Dr. Ronald R. Watson, Professor of Public Health Research, PO Box 245155, 1501 N. Campbell Ave., University of Arizona School of Medicine, Arizona Health Science Center, Tucson, AZ 85724, USA; Fax: (520) 626-6093; email: email@example.com