OBJECTIVE AND CONCLUSIONS: This article gives an overview of observational and experimental epidemiological studies relating
beta-carotene to risk of
cancer and
cardiovascular disease. Observational epidemiological studies have consistently shown that a diet rich in
beta-carotene-rich fruits and vegetables or high blood levels of
beta-carotene are associated with a reduced risk of
cancer at a number of common sites, such as lung and stomach. For other
cancer sites, such as prostate and breast, the observational evidence is not very consistent or absent altogether. For
cardiovascular disease, observational studies are less numerous but do point to a protective effect of high
beta-carotene intake. The associations from observational epidemiology may indeed be ascribed to
beta-carotene, since a number of plausible preventive mechanisms have been demonstrated for
cancer as well as
cardiovascular disease. However, observational epidemiology cannot resolve the question whether other constituents from fruits and vegetables or other factors may explain the findings from the case-control and cohort studies. The results of intervention studies undertaken so far are disappointing and do not indicate a preventive potential for
beta-carotene. Further intervention trials with longer follow-up may be needed to elucidate whether
beta-carotene is protective against certain forms of
cancer and against
cardiovascular disease.