Passive Smoking Linked to Lower levels of Some Micronutrients in the Blood.

Researchers from the Johns Hopkins School of Public Health have found that nonsmokers living with smokers tended to have lower serum concentrations of the antioxidants alpha- and beta-carotene than did persons living in households with no smokers. The research also found that passive smoking was associated with lower levels of total carotenoid and of a particular carotenoid known as cryptoxanthin. (Carotenoids are yellow-to-red pigments found in many vegetables and animal fats that are convertible to vitamin A.) The study appeared in the American Journal of Clinical Nutrition.

There has long been controversy about the associations between passive smoking and adverse health outcomes. The Johns Hopkins study helps narrow the debate. According to lead author Anthony Alberg, Ph.D., M.P.H., assistant professor of epidemiology, "The fact that these are the micronutrients already known to be significantly reduced in active smokers indicates that the associations we found with passive smoking are probably genuine." Antioxidant nutrients protect human cells from damage caused by free radicals, highly reactive oxygen compounds circulating in the body.

The researchers analyzed frozen blood samples collected in 1974 from 1,590 residents of Washington County, Maryland, as well as a smoking survey of the same residents conducted in 1975, and compared exposures to passive smoking at home with micronutrient levels in the subjects' blood samples.

Among persons not currently smoking, those living with smokers tended to have lower serum concentrations of total carotenoid, alpha- and beta-carotene, and cryptoxanthin than did those who lived in households with no smokers. The nutrients not associated with active smoking--vitamins E and A, as well as several other carotenoids (lutein, zeaxanthin, and lycopene)--showed little evidence of being associated with exposure to passive smoking.

The results pose questions for future studies: Does passive smoke directly attack and deplete antioxidant micronutrients? Or does the well-known fact that cigarette smokers have poorer diets than nonsmokers mean that households in which someone smokes generally consume fewer fruits and vegetables than do nonsmoking households, resulting in lowered concentrations of micronutrients?