Evidence of a role for fat-free body mass in modulation of plasma carotenoid concentrations in older men: Studies with hydrodensitometry

We examined the relationship between body composition and changes in plasma carotenoid concentration in response to dietary carotenoid restriction or beta-carotene (beta C) supplementation in healthy older men. Subjects (mean age 65 y) were assigned randomly to supplement (30 mg beta C/d) or placebo groups, and all subjects consumed a standard low carotenoid basal diet plus 1.5 mg beta C/d as carrots. Body composition was measured at baseline by hydrodensitometry, and plasma carotenoids were measured at baseline and after 28 d of treatment by HPLC. Baseline plasma total carotenoid concentration was significantly and negatively correlated with body mass index (BMI) and fat-free mass (FFM) but not with fat mass, whereas baseline beta C concentration was negatively associated with all three variables. The increase in plasma beta C concentration in response to beta C supplementation was significantly and inversely correlated with BMI and FFM but not with fat mass. Likewise, the decline in plasma total carotenoid concentration in the placebo group was also significantly and inversely related to BMI and FFM but not to fat mass. Thus, FFM seems to be an important determinant of plasma carotenoid concentrations and to explain a substantial portion of the often-observed relationship between BMI and blood carotenoid levels. Fat-free mass seems to represent a dynamic reservoir that dampens short-term changes in plasma carotenoid concentrations during fluctuation in carotenoid intake.