Effect of age, lifestyle and dietary factors on bone health and weight in young women

Osteoporosis and obesity are two major health problems in the U.S. In these studies, the age of attaining peak bone mass and the impact of dietary factors, especially calcium and magnesium, in young women were studied. The influence of dietary intake of micronutrients, including calcium, on change in body weight and body composition was also investigated. Bone mineral density (BMD) at spine, femoral neck, greater trochanter, Ward\u27s triangle, and bone mineral content (BMC) and bone surface area (BSA) at spine were assessed in 300 healthy females (aged 6–32 years). At the spine, femoral neck, greater trochanter, and Ward\u27s triangle, 99% of peak BMD is attained by the age of 23.0 ± 1.4, 18.5 ± 1.6, 14.2 ± 2.0, and 15.8 ± 2.1 years, respectively. The age of attaining peak BMC and BSA at spine cannot be estimated as slight, yet significant, increases in these two measures were observed throughout this age group. Age, weight, and height, but not calcium intake, were all significantly associated with all these bone measurements. Diet records from 174 healthy Caucasian females, aged 18–31 years, originally recruited for an exercise intervention study were used in the analysis for the relationship between magnesium intake and bone health. Cross-sectionally, magnesium intake was positively associated with spine BMC and BSA as well as BMD at femoral neck even after controlling for weight and/or age. In 52 subjects who completed the two-year exercise intervention, there was a non-significant positive association between magnesium intake and changes in spine and femoral neck BMD over two years in the exercising subjects. Therefore magnesium intake may have a positive effect on bone health in Caucasian females. The relationships between nutrients, including dairy calcium, and changes in body weight and composition over two years was investigated in the same cohort. Total calcium/kilocalories and vitamin A together were associated with (negatively and positively, respectively) changes in body weight (R 2 = 0.19) and body fat (R2 = 0.27). There was an interaction of calcium and energy intake associated with changes in body weight, such that only at lower energy intakes, calcium intake was related to change in body weight