|Cupples, L adrienne|
Submitted to: Journal of Bone and Mineral Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/29/2008
Publication Date: 1/5/2009
Citation: Sahni, S., Hannan, M.T., Gagnon, D., Blumberg, J., Cupples, L., Kiel, D.P., Tucker, K. 2009. Protective effect of total and supplemental vitamin C intake on the risk of hip fracture - A 17-year follow-up from the Framingham Osteoporosis Study. Journal of Bone and Mineral Research. DOI:10.1359/JBMR.090102. Interpretive Summary: More than 1.5 million Americans experience osteoporotic fractures each year with an annual cost of nearly $14 billion to the US healthcare system. Among 50-year old Caucasian women, the lifetime risk of hip, spine, or forearm fracture is approximately 40%. Of these fractures, hip fractures are the most serious, as they almost always result in hospitalization, lead to permanent disability in about 50% of the cases, and are fatal in approximately 20% of the cases. Studies have consistently shown that higher fruit and vegetable intake has positive effects on bone mineral status. There is evidence that reactive oxygen intermediates may be involved in the bone-resorptive process and that dietary antioxidants such as vitamin C, are capable of decreasing this oxidative stress. In addition, bone matrix contains over 90% of protein as collagen and vitamin C is an essential cofactor for collagen formation. Therefore, vitamin C may help in strengthening bone and preventing fractures. We evaluated associations between intake of total, supplemental and dietary vitamin C and the risk of hip fracture as well as non-vertebral osteoporotic fracture in the Framingham Osteoporosis Study. We found protective associations for higher levels of total and supplemental vitamin C with hip fracture and non-vertebral osteoporotic fracture over 17-y of follow-up in this population of elderly Caucasian men and women. No statistically significant associations were observed with dietary vitamin C intake, after adjusting for supplement use. More studies are needed to examine these associations in other populations.
Technical Abstract: Dietary antioxidants such as vitamin C may play a role in bone health. We evaluated associations of vitamin C intake (total, dietary and supplemental) with incident hip fracture and non-vertebral osteoporotic fracture, over a 15 to 17-y follow-up, in the Framingham Osteoporosis Study. 366 men and 592 women (mean age 75 +/- 5 y) completed a food frequency questionnaire (FFQ) in 1988-89 and were followed for non-vertebral fracture until 2003 and hip fracture until 2005. Tertiles of vitamin C intake were created from estimates obtained using the Willett FFQ, after adjusting for total energy. Hazard ratios (HR) were estimated using Cox-proportional hazards regression, adjusting for covariates. A total of 100 hip fractures occurred over a 17-y follow-up. Subjects in the highest tertile of total vitamin C intake had significantly fewer hip fractures (HR T3: 0.56, P = 0.04, P trend = 0.04) and non-vertebral fractures (HR T3: 0.64, P = 0.04, P trend = 0.04) as compared to subjects in the lowest tertile of intake. Subjects in the highest tertile of supplemental vitamin C intake had a significantly fewer hip fractures (HR T3: 0.31, P = 0.007, P trend = 0.02) and tended to have fewer non-vertebral fractures (HR T3: 0.58, P = 0.10, P trend = 0.06) compared to subjects in the lowest tertile of intake. Although a similar directional trend was observed for dietary vitamin C and risk of fracture, this did not reach significance (P > 0.10). These results suggest a possible protective effect of vitamin C on bone health in older adults.