Relationship of vitamin D and parathyroid hormone with obesity and body composition in African Americans

P>Background Obesity disproportionately affects African Americans (AA) (especially women), and is linked to depressed 25-hydroxyvitamin D (25-OH D) and elevated parathyroid hormone (PTH). The relationship of 25-OH D and PTH with body composition and size in AA is not well known. Objective To determine the relationship of 25-OH D and PTH levels with body composition and anthropometric measures. Design A cross-sectional study was conducted in 98 healthy, overweight, adult AA enrolled in an NIH/NIEHS-sponsored weight loss/salt-sensitivity trial. Measurements Multivariable linear regression analyses were used to explore the relationship of 25-OH D and PTH with body composition, determined by dual-energy X-ray absorptiometry, and anthropometric measures. Body composition and size were contrasted across vitamin D/PTH groups using general linear models: (i) normal (25-OH D > 50 nmol/l, PTH < 65 pg/ml), (ii) low 25-OH D and normal PTH and (iii) low 25-OH D and high PTH. Results Age, gender and season-adjusted regression analyses showed that PTH was directly correlated with total (P = 0 center dot 02), truncal (P = 0 center dot 03) and extremity (P = 0 center dot 03) fat mass, while 25-OH D was inversely related to truncal fat mass (P = 0 center dot 02). Total fat mass in groups 1-3, respectively, was 30 center dot 0, 34 center dot 0 and 37 center dot 4 kg (P = 0 center dot 008); truncal fat mass was 13 center dot 4, 15 center dot 9 and 17 center dot 6 kg (P = 0 center dot 006) and extremity fat mass was 15 center dot 8, 16 center dot 9 and 19 center dot 7 kg (P = 0 center dot 02). Lean mass did not differ across the three groups. Conclusions Our findings show that lower 25-OH D and raised PTH are both correlated, though in opposite directions, with fat mass, fat distribution and anthropometric measures in adult AA.