Objective: To clarify the effects of nutrient/food intake and lifestyle, especially exercise, on calcaneal bone mass in both male and female high school students.
Methods: A total of 798 healthy Japanese high school students (281 boys and 517 girls) were recruited, and their calcaneal bone was assessed by ultrasound using Lunar Achilles. The subjects were thereby divided into a lower bone mass group and a normal bone mass group according to stiffness at the cut-off level of 90 for the boys, and 77 for the girls. Information on lifestyle including frequency of food consumption and regular exercise during the period at junior high school and high school was collected by questionnaire. Nutrient intake was assessed by a semi-quantitative food frequency questionnaire.
Results: 1. The intake of total energy and fat in the lower bone mass group was lower than in the normal bone mass group in both sexes. 2. The frequency of subjects not consuming milk in the lower bone mass group was higher than in the normal bone mass group in both sexes. In the boys, the frequency of the subjects who liked to eat green vegetables in the lower bone mass group was lower in the normal bone mass group. 3. The mean stiffness for subjects undertaking exercise during junior high school was higher than in subjects not exercising, even after adjustment for age in both sexes. The frequency of subjects with a habit of sun bathing in the lower bone mass group was significantly lower than in the normal bone mass group in the girls. 4. An analysis using a logistic model was performed to select the factors related to lower bone mass without being confounded with other factors. Lower energy intake in boys and lower fat intake, no exercise during high school life and no milk consumption in girls were each independently related to lower bone mass.
Conclusion: These results suggest that nutrition and exercise habit affect calcaneal bone mass in high school students of both sexes, especially milk consumption being an important factor related to bone mass in girls.