The objective of the present study was to investigate the nutritional status from the aspect of bone metabolism in Japanese elite male athletes with increased
bone resorption. Urinary levels of a
bone resorption marker, cross-linked N-terminal telopeptide of
type 1 collagen (NTX), were measured in 71 professional baseball players (age, 18-39 years); the mean urinary NTX level was 65.6 (range, 17.5-269.0) nM BCE/mM Cr. Of 71 athletes, 9 with high levels of urinary NTX (greater than mean + 1 SD) were examined by measuring serum
biochemical markers and nutritional assessment (simple food frequency questionnaire). Serum
biochemical marker analysis showed that 7 of these 9 athletes had
vitamin D insufficiency, as indicated by low serum levels of
25-hydroxyvitamin D, and that all 9 athletes showed
vitamin K insufficiency as indicated by low levels of
vitamins K(1) and K(2). Nutritional assessment revealed high intakes of
protein and low intakes of
calcium and
vitamin D based on adequate intake (AI). However, daily
vitamin K intake achieved the AI. These results suggest that there exist elite male athletes who show increased
bone resorption and
calcium and
vitamin D insufficiency. However, there was a discrepancy between
vitamin K intake and serum levels of
vitamins K(1) and K(2). The present study raised an issue regarding the nutritional status from the point of view of bone metabolism in elite male athletes such as professional baseball players.