ISMNT NEWS: Disease Prevention by Exploring Molecular Mechanisms Linked to Nutrition

ISMNT News #20 demonstrates that an increased beta-carotene (15 mg daily) intake can enhance cell-mediated immune responses relatively shortly, providing a potential mechanism for the anticarcinogenic properties attributed to beta-carotene. It would obviously be of great interest to look into possible effects on cardiovascular diseases which are influenced by the immune system, e.g. myocarditis.

The key reference is by:

Hughes DA, Wright AJ, Finglas PM, Peerless AC, Bailey AL, Astley SB, Pinder AC, Southon S


Department of Nutrition, Diet, and Health, Institute of Food Research, Colney, Norwich, UK. in

J Lab Clin Med 1997 Mar;129(3):309-317

Although there is strong epidemiologic evidence that diets rich in carotenoids such as beta-carotene are associated with a reduced incidence of cancer, the cellular mechanisms underlying this phenomenon remain unknown.

This article describes the effect of dietary beta-carotene supplementation on both the expression of functionally associated surface molecules on human monocytes and on the secretion of the cytokine tumor necrosis factor-alpha (TNF-alpha) by monocytes, all of which are involved in the initiation and regulation of immune responses involved in tumor surveillance.

A double-blind, placebo-controlled, crossover study was undertaken in which 25 healthy, adult male nonsmokers were randomly assigned to receive beta-carotene (15 mg daily) or placebo for 26 days, followed by the alternative treatment for a further 26 days. The expression of functionally related monocyte surface molecules was quantified by flow cytometry, and ex vivo secretion of TNF-alpha was quantified by an enzyme-linked immunosorbent assay, before and after each treatment period.

After dietary supplementation there were significant increases in plasma levels of beta-carotene and in the percentages of monocytes expressing the major histocompatibility complex class II molecule HLA-DR and the adhesion molecules intercellular adhesion

molecule-1 and leukocyte function-associated antigen-3. In addition, the ex vivo TNF-alpha secretion by blood monocytes was significantly increased after supplementation.

These findings suggest that moderate increases in the dietary intake of beta-carotene can enhance cell-mediated immune responses within a relatively short period of time, providing a potential mechanism for the anticarcinogenic properties attributed to beta-carotene.