CORRECTION: Carotenoids may lower diabetes risk in nonsmokers

[Corrects story posted May 23, 2006. Deletes redundant word (nonsmokers) from first sentence, and revises paragraph for clarity.]

NEW YORK (Reuters Health) - For people who don't smoke, the risk of developing diabetes is lower in those with higher levels of carotenoids in their blood, according to a new report. The effect is not seen in smokers, however.

Carotenoids -- plant-derived antioxidants found in vegetables such as carrots, tomatoes and spinach -- may reduce the risk of diabetes by cutting oxidative stress, the authors of the study explain in the American Journal of Epidemiology. Likewise, high levels of carotenoids may help reduce the oxidative stress caused by cigarette smoking.

Previous reports have linked smoking with low levels of carotenoids. Moreover, in other studies, high carotenoid levels have been tied to a reduced risk of diabetes. However, it was unclear if the rare smoker with a high carotenoid level still enjoyed a decreased risk of diabetes.

To investigate, Dr. David R. Jacobs, from the University of Minnesota School of Public Health in Minneapolis, and colleagues analyzed data from 4493 subjects, between 18 and 30 years of age, enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study. The study focused on the 148 cases of diabetes that arose during follow-up from 1985 to 2001.

In nonsmokers, increasing carotenoid levels at the start of the study were associated with decreasing risk of developing diabetes. In smokers, however, this was not seen and high carotenoid levels were actually associated with a slight increase in risk.

The findings "suggest that smoking may nullify the protective effect (of high carotenoid levels), supporting the concept that antioxidant metabolism and the oxidative defense system behave differently in smokers than in nonsmokers," the authors conclude.

SOURCE: American Journal of Epidemiology, May 15, 2006.