Favorable effect of dietary vitamin C on bone mineral density in postmenopausal women (KNHANES IV, 2009): discrepancies regarding skeletal sites, age, and vitamin D status

Dietary vitamin C intake showed significant positive associations with BMD in postmenopausal women, especially with vitamin D deficiency. Introduction Although there is a positive role of vitamin C in osteoblastogenesis, debate remains about the contribution of vitamin C to bone mineral density (BMD) in humans. Methods Data were derived from the Fourth Korean National Health and Nutrition Examination Survey. Dietary information was assessed using a 24-h dietary recall questionnaire. BMD was measured by dual-energy X-ray absorptiometry at the lumbar and hip. Results A total of 1,196 postmenopausal women aged 50 years and older were stratified into tertiles by daily dietary vitamin C intake. After adjusting for traditional confounders, dietary vitamin C intake tertile was significantly positively associated with BMD at all sites (R=0.513 for lumbar spine (LS) and R=0.657 for femoral neck (FN), P < 0.05 for each). The subjects with osteoporosis had significantly lower dietary vitamin C intake than did subjects without osteoporosis (74.4 +/- 66.2 vs 94.1 +/- 78.6 mg/day for LS and 65.5 +/- 56.6 vs 94.3 +/- 79.2 mg/day for FN, respectively, P < 0.001). The multiple-adjusted odds ratio for osteoporosis for dietary vitamin C < 100 mg/day was 1.790 (95 % CI 1.333-2.405, P < 0.001). However, the significant association between vitamin C intake and BMD was only observed in subjects with vitamin D deficiency and aged 50-59 years or > 70 years. Conclusion Dietary vitamin C intake was positively associated with BMD in postmenopausal women, and inadequate vitamin C intake could increase the risk of osteoporosis.