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[Purpose] The current study aimed to determine the association between serum uncarboxylated osteocalcin (ucOC) levels and dietary vitamin K intake in female Japanese athletes.[Methods] The nutritional profile and food group intake of 52 Japanese female athletes were investigated using a digital photographic method with data obtained from 3-day dietary records. The food groups were categorized into 18 groups in line with the standard tables of food composition in Japan. Fasting blood samples were collected for serum ucOC levels, and dual-energy X-ray absorptiometry (DXA) evaluated body composition and bone parameters.[Results] The results showed that dietary vitamin K intake level was 235 ± 148 µg/day, and approximately 70% (n = 36) of participants consumed more than the adequate intake (AI) level, based on the Dietary Reference Intakes for Japanese females aged 18–29. Serum ucOC levels were negatively associated with daily vitamin K intake (r = −0.388, <i>P</i> = 0.004) and calcium (r = −0.596, <i>P</i> = 0.004) after adjusting for energy intake.[Conclusion] Our study revealed that serum ucOC levels were negatively associated with dietary vitamin K intake in female Japanese athletes. Serum ucOC levels reflected dietary vitamin K intake in female athletes. In summary, female athletes consume more vitamin K than the general population to maintain bone health. Furthermore, our results indicated that serum ucOC levels might be linked to dietary calcium intake.

The aim of the present study was to clarify the influence of inulin and lactulose-fortified prebiotic food intakes on bone metabolism turnover among Japanese female athletes. The participants included 29 female athletes aged 18–25 years. They were requested to consume their habitual foods or drinks with one pack of prebiotic food every day for 12 weeks. Dietary intake, training time, body composition, blood sample, and fecal microbiota were assessed during this intervention period. Body composition, total energy intake, and training time of the participants revealed no significant changes during the intervention period. The occupation ratio of Bifidobacterium spp. was significantly increased at 3 and 4 weeks (18.0 ± 8.3% and 17.6 ± 8.5%, respectively) compared to that of pre-intervention (11.7 ± 7.3%) (p = 0.019 and p = 0.035, respectively). The serum TRACP-5b level was significantly decreased at 12 weeks (363 ± 112 mU/dL) compared to that at baseline (430 ± 154 mU/dL) (p = 0.018). These results suggest that the prebiotic food used in this study might have beneficial effects on bone health and gut microbial environment among female athletes. Further studies are warranted to identify the mechanism of the prebiotics–gut–bone axis.

Objectives:The aim of the present study was to identify the habitual dietary intake and stress fractures history among sport types and to determine the factors related to the risk of stress fractures among Japanese female collegiate athletes. Methods: This study involved 589 Japanese female collegiate athletes. We investigated habitual dietary intake (food frequency questionnaire), eating attitude (EAT-26), demographics, training status, participation in sports events, history of injury in their career, and menstrual status using a self-reported questionnaire. A multivariate logistic regression analysis was conducted to determine the risk factors associated with stress fractures. Results: Thirty percent of the total participants had a history of stress fractures, although most participants had no risk of eating disorders. Most Japanese female collegiate athletes consumed less than the dietary reference intake levels for the general Japanese female population aged 18-29 years and the athletes' dietary guideline for key bone-health nutrients such as calcium and vitamin D. The multivariate logistic regression analysis revealed body mass index (BMI; OR, 0.91; 95% CI, 0.82-0.99) and energy intake (EI; OR, 0.99; 95% CI, 0.99-0.99) as significant and independent factors in the history of stress fractures among Japanese female collegiate athletes (p ¼ 0.047 and p ¼ 0.039, respectively). Conclusions: Japanese female collegiate athletes failed to meet energy and nutrient recommendations; BMI and EI were significantly associated with stress fractures, a diet that includes an appropriate amount of energy is essential.

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