Associations of Lifestyle Factors with Bone Mineral Density among Male University Students in Japan

To investigate associations of lifestyle factors with bone mineral density among young men in Japan, we measured bone mineral density of the second metacarpal bone in 143 male university students, aged 18-22 years, by the computed X-ray densitometry. The subjects completed a lifestyle questionnaire including a quantitative food frequency questionnaire. Their mean±standard deviation of bone mineral density was 2.61±0.23 mmAl. Body mass index (Spearman’s ρ=0.232, p=0.006), daily walking time (ρ=0.186, p=0.028), and milk consumption at junior (ρ=0.250, p=0.003) and senior (ρ=0.195, p=0.020) high school were significantly correlated with the bone mineral density. For nutritional variables, the bone mineral density was positively correlated with energy-adjusted intakes of calcium (Pearson’s r=0.302, p=0.0002), potassium (r=0.265, p=0.001), saturated fatty acids (r=0.211, p=0.011), and magnesium (r=0.173, p=0.039), and with those of milk and dairy products (r=0.228, p=0.006) and fruits (r=0.205, p=0.014), while being negatively associated with energy-adjusted noodle consumption (r=-0.185, p=0.027). The positive correlation of milk consumption at junior high school with the bone mineral density was not materially altered by adjustment for the body mass index, calcium intake, and walking time. Single-life students had lower bone mineral density compared with those lived with families (p=0.044). Bone mineral density could be increased by modifying dietary habits in young men.