A new US study reports that low blood concentrations of beta-carotene and vitamin C seem to be associated with increased early indicators for insulin resistance, cardiovascular diseases and cancer in an ethnic group-dependent manner.
To investigate a potential ethnic group-dependent link between micronutrient levels and the risk for chronic diseases, blood concentrations of vitamin A, C, E and beta-carotene as well as early biomarkers of insulin resistance and inflammation (C-reactive protein and leukocytes) were analyzed in 176 non-smoking, healthy, white, and African American adults aged 18–65 years (1). The study results showed that low beta-carotene levels were significantly associated with an increased risk for insulin resistance among African American participants, whereas, these same associations were not significant for whites. Lower vitamin C levels were associated with higher leukocyte count only in African Americans but not whites. For all participants, lower beta-carotene levels were linked to higher C-reactive protein concentrations. The analysis of vitamin con- centrations and adjustment for vitamin supplement use revealed no significant ethnic group differences in vitamin C, vitamin E, and beta-carotene. African-Americans, however, had a significantly lower mean ad- justed concentration of vitamin A.
The researchers commented that whether or not lower levels of micronutrients contribute uniquely to ethnic group health disparities is a worthwhile aim for future research. They speculated that a potential cause for the difference with regard to beta-carotene may be a lower conversion rate of beta-carotene to vitamin A (lower beta-carotene monooxygenase activity) of African Americans, relative to whites. When comparing African Americans to whites, it is clearly evident that African Americans have higher mortality rates from type 2 diabetes and cardiovascular disease (2). It has been reported that cardio-metabolic conditions and various forms of cancers are closely linked to dietary intake and blood levels of micronutrients. The most consistent findings have been reported for carotenoids where both dietary intake and serum concentrations have been inversely related to occurrence of type 2 diabetes and CVD mortality (3). As suggested by a recent meta-analysis, lower levels of carotenoids are also associated with an increased risk of breast cancer (4). Surprisingly, ethnic group differences in early risk factors of cardio-metabolic conditions and some forms of cancer, such as hyperinsulinemia and insulin resistance, have not been associated with ethnic group dif- ferences in dietary intake (2).