An inverse association between calcium and adiposity in women with high fat and calcium intakes.

Objectives: To assess the association between calcium intake and body composition in African Black and White women.

Design: Cross-sectional survey.

Setting: Metabolic unit.

Participants: A convenience sample of 106 White and 102 Black healthy urban women, 20-50 years old, stratified for body mass index (BMI).

Main Outcome Measures: Dietary calcium intake, fat intake, BMI, percentage body fat, fasting plasma glucose and insulin, homeostasis model assessment of insulin resistance (HOMA-IR), oral glucose tolerance test (OGTT), blood pressure.

Methods: After an overnight fast, weight, height and blood pressure were measured, subjects underwent a 75-g OGTT, and blood samples were taken. Food frequency questionnaires were completed, and body composition was measured by anthropometry and air displacement plethysmography.

Results: Mean calcium and fat intakes were significantly higher in White women (1053.8 mg/day and 103.1 g/day, respectively) than in the Black women (523 mg/day and 69.2 g/day), resulting in higher calcium:fat-intake ratio in White women. After adjustment for age and total energy intake, significant negative correlations were found between calcium intake and fasting insulin (r = -.337, P = .01) and HOMA-IR (r = -.334, P = .01) in the White subjects. The calcium:fat ratio correlated negatively with BMI (r = -.328, P < .012), percentage body fat (r = -.336, P = .01), fasting insulin (r = -.374, P = .004), postprandial insulin (r = -.328, P = .01), and HOMA-IR (r = -.365, P = .005). In the Black subjects, a significant negative correlation was found between calcium intake and blood pressure.

Conclusion: The association between calcium intake and percentage body fat, BMI, fasting glucose, and insulin were significant only with high intake of fat and calcium, which is not characteristic of the habitual diet of African women.