BACKGROUND: Immune cells generate free radicals as part of their normal activity, fighting bacteria and destroying virus-infected cells. Although the body produces a variety of protective antioxidant enzymes, free-radical stresses can overwhelm these antioxidants. Previous research has shown that dietary antioxidants can enhance the immune response.
RESEARCH: In this review article, researchers focused primarily on the immune enhancing effects of beta-carotene and lutein, natural antioxidant carotenoids found in a variety of vegetables. Information on some mechanisms of carotenoids' anti-tumor activity also was presented.
RESULTS: Animal and human studies have found that beta-carotene can enhance many aspects of immunity. Some of this research has shown that beta-carotene boosts the activity of "natural-killer" cells, a type of immune cell that fights cancer. Similarly, animal studies have shown that large dosages of lutein can inhibit tumor growth in breast tissue in laboratory animals. Beta-carotene, lutein, and other carotenoids work in a variety of ways, such as by maintaining normal cell-membrane function and cell-to-cell communication. These carotenoids also influence gene activity. For example, lutein increases the activity of the p53 gene.
IMPLICATIONS: This review article describes many of the beneficial roles that carotenoids play in maintaining normal immunity and reducing excess levels of free radicals. The researchers observed that recent studies on carotenoids "have advanced our knowledge on the possible mechanism by which carotenoids regulate immune function and cancer."
Chew BP, Park JS. Carotenoid action on the immune response. Journal of Nutrition, 2004;134:257S-261S.
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