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

Abstract

Vitamin C may play a role in bone health. In the Framingham Study, subjects with higher total or supplemental vitamin C intake had fewer hip fractures and non-vertebral fractures as compared to subjects with lower intakes. Therefore, vitamin C may have a protective effect on bone health in older adults.

Introduction: 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-year follow-up, in the Framingham Osteoporosis Study.

Methods: Three hundred and sixty-six men and 592 women (mean age 75 +/- 5 years) completed a food frequency questionnaire (FFQ) in 1988-1989 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 (residual method). Hazard ratios were estimated using Cox-proportional hazards regression, adjusting for covariates.

Results: Over follow-up 100 hip fractures occurred. Subjects in the highest tertile of total vitamin C intake had significantly fewer hip fractures (P trend = 0.04) and non-vertebral fractures (P trend = 0.05) compared to subjects in the lowest tertile of intake. Subjects in the highest category of supplemental vitamin C intake had significantly fewer hip fractures (P trend = 0.02) and non-vertebral fractures (P trend = 0.07) compared to non-supplement users. Dietary vitamin C intake was not associated with fracture risk (all P > 0.22).

Conclusion: These results suggest a possible protective effect of vitamin C on bone health in older adults.

Fig. 1

Flowchart showing total number of subjects enrolled in the Framingham Heart Study and the final number of subjects included in the analyses ^a Framingham Heart Study ^b Food Frequency Questionnaire

Fig. 2

Inverse association of total vitamin C intake and risk of (a): Hip fracture and (b): Non-vertebral osteoporotic fracture in the elderly men and women of the Framingham Osteoporosis Study a HR is significantly different from HR of tertile 1: * P<0.05 P for trend=0.04 for hip fracture and 0.05 for non-vertebral osteoporotic fracture ^a Full models were adjusted for sex and estrogen use (group 1: men, group 2: never or former estrogen users, group 3: current estrogen users), age at exam 20 (yr), BMI (kg/m²), height at exam 1 (m), total energy intake (MJ), and multivitamin use (yes/no)

Fig. 3

Inverse association of vitamin C intake from supplements a and risk of (a): Hip fracture and (b): Non-vertebral osteoporotic fracture in the elderly men and women of the Framingham Osteoporosis Study b HR is significantly different from HR of tertile 1: * P<0.05, † P=0.1 P for trend=0.02 for hip fracture and 0.07 for non-vertebral osteoporotic fracture ^a Vitamin C from supplements was categorized as (group 1: non-supplement users, group 2: intake < 75 mg/d, group 3: intake ≥ 75 mg/d) ^b Parsimonious models were adjusted for dietary vitamin C intake (mg), sex and estrogen use (group 1: men, group 2: never or former estrogen users, group 3: current estrogen users), age at exam 20 (yr), BMI (kg/m²), height at exam 1 (m), total energy intake (MJ), Physical Activity Index, and multivitamin use (yes/no)