[Relationship between dietary calcium and bone mineral density before menopause]

To study the relationship between dietary calcium intake and bone mineral density (BMD) among young Japanese females, we recruited 1298 females under 40 years living in Yokohama city for BMD measurement by Computed X-ray densitometer (CXD method) and dietary questionnaire. 1. The average of BMD was 2.75 mm/AI and was highest in the 35 to 39 year old group. 2. Calcium intake (Ca) and protein intake (Protein) were highest in 35 to 39 year old group. 3. BMD, Ca, and Protein were significantly higher in those who had regular dietary habits than those with irregular habits. 4. Among those who had lower Ca, (less than 600 mg per day), the amount of small fish consumed whole was negatively correlated with BMD (p = 0.035), and those with higher consumption of small fish than average had significantly (p = 0.018) lower BMD than those with lower small fish consumption adjusting for age and Ca and protein intake. These findings imply a possibility that small fish accompanied by higher salt intake may influence BMD adversely in this population by an interaction with calcium urinary excretion, which has been suggested by experimental and epidemiologic studies. Dietary composition of Ca may be important for prevention of osteoporosis.