SAN JUAN, PUERTO RICO—That smokers have low vitamin C levels is well known. Research now confirms that children exposed to environmental tobacco smoke (ETS) also have markedly decreased ascorbic acid levels—even when they live in well-ventilated homes.[1]

Two years ago, data from the Third National Health and Nutrition Examination Survey (NHANES III) demonstrated that among the estimated 43% of all children in the US who live in homes with a smoker, plasma vitamin C levels are inversely associated with ETS exposure and levels of cotinine, a marker for tobacco smoke exposure.[2] A new study suggests that even low levels of ETS exposure may detrimentally affect ascorbic acid levels. The study focused on children in Cataño, Puerto Rico, where one might expect household smoke exposure to be milder than in mainland communities. “The kids that we sampled … don’t have a lot of intensive smoke concentration in the same way we would in the States or other northern-climate countries,” explained primary author Alan M. Preston, PhD, Professor of Biochemistry at the University of Puerto Rico in San Juan. “We are in an almost ideal type of environment [in] a tropical setting—we have open windows, we have fans.” Yet, said Dr. Preston, “We’re seeing about a fourth of the effect of reduction of plasma vitamin C in very mildly exposed kids compared to the reduction in adults who are smoking full time—which is kind of remarkable.”

Dr. Preston and colleagues studied 512 healthy children ages 2 to 12 who visited the Pediatric Care Clinic of the Cataño Health Center. Surveys examined dietary intake of vitamin C as well as the smoking status of the children’s parents. As a measure of smoke exposure, urine samples were tested for cotinine, and blood samples revealed plasma ascorbic acid levels.

Fifty percent of the children lived in households with one or more smokers; as expected, these children excreted significantly more cotinine than did children of nonsmokers. Mean dietary intakes of vitamin C for all groups were above the recommended daily allowance (RDA) for children ages 2 to 12, and they did not differ between children from smoking and nonsmoking households.

However, plasma vitamin C levels among ETS-exposed children were significantly lower than those among children from nonsmoking homes—by an average of 3.2 mmol/L. A previous study had found levels in smoking and nonsmoking adults to differ by 11.4 mmol/L, on average.[3]

Because intakes were generally well above the RDA, even children of smokers were probably not deficient in vitamin C. But, said Dr. Preston, “Our concern is that if the kids are getting marginal levels of vitamin C—say, below 40 mg/d—then this lowering might have a substantial effect” on antioxidant status and health. He and his coworkers therefore recommend that children who live with adults who smoke eat a diet high in vitamin C–rich foods or take a vitamin supplement.

—Mimi Zucker, PhD