Race differences in the relation of vitamins A, C, E, and β-carotene to metabolic and inflammatory biomarkers

Abstract

Using archival data, we conducted a secondary analysis to examine race-differences in the relation of serum vitamins A, C, E and β-carotene to insulin resistance (IR), fasting insulin and glucose, high sensitivity C-reactive protein (hsCRP), and leukocyte count in 176 non-smoking, healthy, white and African American (AA) adults aged 18-65 years (48% women, 33% AA). We hypothesized that micronutrient concentrations would be associated with early risk markers of cardiometabolic diseases in a race-dependent manner. Fasting blood samples were analyzed for micronutrients, insulin, glucose, hsCRP, and leukocyte count. Insulin resistance was estimated using the homeostatic model assessment (HOMA). After adjusting for age, body mass index, gender, educational level, use of vitamin supplements, alcohol intake, leisure time physical activity, menopausal status, and total cholesterol, we observed that β-carotene was significantly associated with insulin resistance and fasting insulin in a race-dependent manner. Among AA, lower β-carotene levels were associated with higher estimates of insulin resistance and fasting insulin; whereas, these same associations were not significant for whites. Race also significantly moderated the relation of vitamin C to leukocyte count, with lower vitamin C being associated with higher leukocyte count only in AA but not whites. For all subjects, lower β-carotene was associated with higher hsCRP. In AA, but not whites, lower levels of β-carotene and vitamin C were significantly associated with early risk markers implicated in cardiometabolic conditions and cancer. Whether or not lower levels of micronutrients contribute uniquely to racial health disparities is a worthwhile aim for future research.

A longitudinal study of pre-pregnancy antioxidant levels and subsequent perinatal outcomes in black and white women: The CARDIA Study

“…This trend was particularly pronounced in Black women. A few studies have found race differences in antioxidant relationships with metabolism: lower β-carotene has been associated with insulin resistance [39] and oxidative stress has been associated with lower insulin sensitivity in African-Americans [40], but these are health-protective, rather than the negative effect we found. Research also suggests that multivitamin use may be particularly protective against low birthweight in Black women [17].…”

β-Carotene Concentration and Its Association with Inflammatory Biomarkers in Spanish Schoolchildren

“…This result highlights the benefit of supplementing with whole foods rather than with individual nutrients to maximise the benefits of nutritional interventions. In addition, in a study involving 176 adult non-smokers aged 18-65, lower levels of serum β-carotene were associated with higher CRP levels [58]. Finally, in another study involving 4,557 non-smokers aged 25-55, the serum levels of 5 carotenoids (α-carotene, β-carotene, β-cryptoxanthin, lycopene, and lutein/zeaxanthin) were significantly lower in those with CRP levels above 0.88 mg/dL ( p = 0.001) [59].…”

Inverse association linking serum levels of potential antioxidant vitamins with C-reactive protein levels using a novel analytical approach

“…In light of suggestions offered by Schwab et al (12) , in relation to the health benefits of combinations of vitamin E and other antioxidants (32) , this study's observed positive association between vitamin E and higher CRP levels is noteworthy. Other small-scale clinical studies have disclosed positive vitamin-E-CRP associations (10,11) , and there is evidence from randomised controlled trials indicating that supplementation of vitamin E may provide no benefit with respect to prevention of cardiovascular events (32) . Indeed, long-term vitamin E supplementation might be predictive of slightly higher risk of heart failure (33) .…”

“…For example, in some studies, lower levels of vitamin C and carotenoids are inversely linked to CRP levels; in other investigations, the estimates are null (5)(6)(7)(8) . Inverse associations of CRP level and vitamin E have been observed, but there are also null estimates, as well as some positive associations (5,7,(9)(10)(11) .…”