JAMA.  Journal of the American Medical Association
March 6 1996 Vol 275 No.9 pp 699-703

Mortality Associated With Low Plasma Concentration of Beta Carotene and the Effect of Oral Supplementation
E. Robert Greenberg, MD; John A. Baron, MD; Margaret R. Karagas, PhD; Therese A. Stukel, PhD;  David W. Nierenbergl. MD- Marguerite M. Stevens, PhD; Jack S. Mandel, PhD, Robert W. Haile, PhD
From the Dartrmouth Medical School and Norris Cotton Cancer Center. Lebanon. NH (Drs Greenberg. Baron. Karagas. Stuke~. Nierenberg. and Stevens): University of Mnnesota School of Public Health. Minneapolis (Dr Mandel): and University of California. LosAngeles. School of Medicine and University ol Southern California School of Medicine (Dr Haile).D

One possibility is that beta carotene is a marker for other dietary or lifestyle factors and that these factors account for the benefit suggested in our population and in other investigations. We lacked detailed dietary information from our study participants, but higher blood concentrations of carotenoids are characteristic of  persons who eat large amounts of vegetables and fruits, and many compounds other than beta carotene in these foods perhaps could reduce risk of cancer and heart disease. For example, fruits and vegetables contain vitamins, selenium. fiber, and other substances that have antioxidant properties or anticarcinogenic effects in laboratory experiments. It is conceivable that the decrease in mortality risk associated with higher initial plasma beta carotene concentrations in our study was actually a manifestation of the conjoint beneficial effects of a number of factors related to diet. If so, programs to change dietary patterns toward consumption of more vegetables, fruits, and grains may prove more effective than altering intake of individual micronutrients such as beta carotene.

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