Vitamin C, vitamin B12, folate and the risk of osteoporotic fractures. A case-control study.

Water-soluble vitamins influence the development of an adequate structure of bone tissue, but there is scant information relating them with osteoporotic fractures. We analyze whether serum vitamin C, vitamin B12, and erythrocyte folate, or dietary intake of vitamin C and folate, are related with osteoporotic fractures in the elderly. A hospital-based case-control study was carried out at the Hospital of Jaén (167 cases, 167 controls), Spain. Cases were defined as patients aged 65 or more years with a low-energy fracture. Controls were people without fracture, matched for age and sex with cases. Diet was assessed by a semi-quantitative food frequency questionnaire. Serum vitamin C was measured using high-performance liquid chromatography (HPLC). Folic acid and vitamin B12 were measured using procedures of competitive or immunometric immunoassay. Multivariable analyses were also fitted to adjust for confounding using analysis of covariance (for the comparison of adjusted means) and conditional logistic regression (for estimating adjusted odds ratios). A statistically significant difference between cases and controls for vitamin C blood levels was found, being higher for controls (p = 0.01). Analysis of the association between serum vitamin C and fracture risk showed a linear trend (p = 0.03) with a significantly reduced risk for the upper quartile (OR = 0.31; 95% CI 0.11-0.87). The intake of vitamin C, folic acid, and B12 was not related to fracture risk, nor was there any association with erythrocyte folate or serum vitamin B12. In conclusion, serum vitamin C levels were lower in cases with osteoporotic fractures than in controls.