Serum And Skin Carotenoid Levels In Older Adults With And Without Metabolic Syndrome

PURPOSE: Metabolic syndrome (MetS), a clustering of cardiovascular disease (CVD) risk factors, is associated with increased mortality risk. There is an inverse dose relationship between CVD mortality and fruit and vegetable (FV) intake. The primary aim of this study is to compare serum and skin carotenoid levels in older adults with and without MetS, and the secondary aim is to determine whether total serum carotenoid level is associated with total skin carotenoid score. METHODS: Older adults (68.0 ± 8.4 yrs. vs. 69.6 ± 7.7 yrs, (Mean ± SD), p = 0.278, non-MetS and MetS, respectively) were assessed on serum carotenoid concentration, reflection spectroscopy (RS) skin carotenoid score, self-reported servings of FV, socio-demographic factors, and comorbid conditions. Unadjusted and adjusted linear regressions were used to evaluate differences in outcomes between those with and without MetS (n = 77 and 63, respectively). RESULTS: Compared to the non-MetS group, those with MetS had 52% lower serum alpha-carotene (66.0 ± 79.1 ng/mL vs. 136.7 ± 143.6 ng/mL, p < 0.001), 39% lower serum beta-carotene (301.2 ± 371.9 ng/mL vs. 491.2 ± 404.3 ng/mL, p < 0.001), and 22% lower total serum carotenoid values (1170.5 ± 767.0 ng/mL vs. 1495.6 ± 837.1 ng/mL, p = 0.002). These results remained significant after adjusting for socio-demographic characteristics and known comorbidities. No group differences were found for serum lycopene, lutein, and cryptoxanthin, skin carotenoid score, or FV intake. Total serum carotenoids were significantly associated with skin carotenoid scores (r = 0.58, p < 0.001) even after adjusting for other confounding factors (p = 0.64, p < 0.001). CONCLUSIONS: Older adults with MetS had significantly lower total serum carotenoids than those without MetS. This was primarily driven by differences in alpha-carotene and beta-carotene. Also, serum and skin carotenoid levels were correlated. The clinical significance is RS skin carotenoid scores could be used as a non-invasive marker of carotenoid status in clinical settings.