Carotenes in Cancer Prevention

Population-based epidemiological studies clearly demonstrate a strong inverse cor­relation between dietary carotene intake and a variety of cancers involving epithelial tissues (lung, skin, uterus, cervix, gastrointestinal tract, etcetera). The epidemio­logical association is much stronger for carotene than for vitamin A. This may reflect carotene’s superior antioxidant, immune-potentiating activity and anticarcinogenic activity.

: No one would argue that a diet high in carotenes is not protective against cancer (except, perhaps, Victor Herbert, M.D., a longtime crusader against nutritional sup­plementation). The big question is, can beta-carotene supplementation reduce the risk of cancer? The answer appears to be no, that on its own beta-carotene supple­mentation does not reduce the risk of cancer. Three highly publicized reports on can­cer prevention trials featuring synthetic all-trans beta-carotene in high-risk groups have produced negative results. However, before we close this issue, let’s take a clos­er look at each of these studies to help put things into perspective.

Alpha-tocopherol, Beta-carotene Cancer Prevention Study Group

Here researchers studied 29,000 men in Finland who smoked and drank alcohol.The men took beta-carotene (20 milligrams daily) and/or vitamin E. The results of this study indicated an 18 percent increase in lung cancer in the beta-carotene group. This result was not unexpected. Studies in primates have demonstrated that when animals ingest alcohol and beta-carotene, they experience an increase in liver dam­age as a result of oxidative damage. Other researchers have pointed out that beta- carotene is very susceptible to oxidative damage. To protect against oxidative damage of beta-carotene, other antioxidant nutrients need to be present. Absence of these protective nutrients could result in the formation of cancer-causing compounds, which further stresses the importance of relying on foods and broader-spectrum nutritional antioxidant support. For example, the group that received both beta- carotene and vitamin E did not show an increase in cancer. In addition, the group that did not receive beta-carotene supplements demonstrated a strong protective effect of high dietary beta-carotene and blood carotene levels against lung cancer. All together this data strongly suggests that the protection offered by beta-carotene is apparent only when other important antioxidant nutrients are present.

Source: Encyclopedia of Nutritional Supplements