Site-specific differences in bone mineral density in black and white premenopausal South African women.

SUMMARY: We examined ethnic differences in bone mineral density (BMD) and the contribution of body composition, lifestyle and socioeconomic factors in South African women. Femoral neck and total hip BMD were higher, but lumbar spine BMD was lower in black women, with body composition, lifestyle and socioeconomic status (SES) factors contributing differently in ethnic groups. INTRODUCTION: There is a paucity of data on the relative contribution of body composition, lifestyle factors and SES, unique to different ethnic groups in South Africa, to BMD. We examined differences in femoral neck (FN), total hip (TH) and lumbar spine (LS) BMD between black and white premenopausal South African women and the associations between BMD and body composition, lifestyle factors and SES in these two ethnic groups. METHODS: BMD and body composition were measured in 240 black (27 ± 7; 18-45 years) and 187 white (31 ± 8; 18-45 years) women using dual-energy X-ray absorptiometry. Questionnaires were administered to examine SES, physical activity and dietary intake. RESULTS: After co-varying for age, FN and TH were higher in black than white women (FN 0.882 ± 0.128 vs. 0.827 ± 0.116 g/cm(2), P < 0.001; TH 0.970 ± 0.130 vs. 0.943 ± 0.124 g/cm(2), P = 0.018). When adjusting for ethnic differences in body composition, LS was higher in white than black women. In black women, fat-free soft tissue mass, SES and injectable contraceptive use explained 33-42% of the variance in BMD at the hip sites and 22% at the LS. In white women, fat-free soft tissue mass and leisure activity explained 24-30% of the variance in BMD at the hip sites, whereas fat mass, leisure activity and oral contraceptive use explained 11% of the variance at the LS. CONCLUSION: FN and TH BMD were higher, but LS BMD was lower in black than white South African women with body composition, lifestyle and SES factors contributing differently to BMD in these women.

The tumor necrosis factor-α gene -238G>A polymorphism, dietary fat intake, obesity risk and serum lipid concentrations in black and white South African women.

BACKGROUND/OBJECTIVES: This study explored interactions between dietary fat intake and the tumor necrosis factor-α gene (TNFA) -238G>A polymorphism (rs361525) on adiposity and serum lipid concentrations in apparently healthy premenopausal black and white South African (SA) women. SUBJECTS/METHODS: Normal-weight (N=107) and obese (N=120) black, and normal-weight (N=89) and obese (N=62) white SA women underwent measurements of body composition, fasting lipids and dietary intake, and were genotyped for the -238G>A polymorphism. RESULTS: Black women had a higher -238GA genotype frequency than white women (P<0.001), but there were no differences between body mass index groups. Black women with the -238A allele had a greater body fat % than those with the GG genotype (P<0.001). Further, in black women, with increasing polyunsaturated:saturated fat ratio and omega-6 (n-6):omega-3 (n-3) ratio, high-density lipoprotein-cholesterol (HDL-C) concentrations decreased, and total cholesterol (T-C):HDL-C ratio increased in those with the GA genotype but not the GG genotype. In addition, with increasing n-3 polyunsaturated fatty acid intake (percentage of total energy intake, %E), T-C:HDL-C ratio decreased in those with the GA genotype, but not in those with the GG genotype. In white SA women, with increasing eicosapentaenoic acid (%E) intake, low-density lipoprotein-cholesterol concentrations decreased in those with the GG genotype but not the GA genotype. CONCLUSIONS: The -238G>A polymorphism was associated with body fatness in black women. Interactions between -238G>A genotypes and dietary fat intake on serum lipids and adiposity differed depending on dietary fat intake, but those for serum lipids were not the same in black and white SA women.