Smoking, antioxidant vitamins, and the risk of hip fracture

Smoking increases the concentrations of free radicals, which have been sugg ested to be involved in bone resorption, We examined whether the dietary in take of antioxidant vitamins may modify the increased hip fracture risk ass ociated with smoking. We prospectively studied 66,651 women who were 40-76 years of age. Forty-four of the cohort members who sustained a first hip fr acture within 2-64 months of follow-up (n = 247) and 93 out of 873 age-matc hed controls were current smokers. Information on diet was obtained by a va lidated food-frequency questionnaire. The relative risk of hip fracture for current versus never smokers was analyzed in relation to the dietary intak e of antioxidant vitamins stratified into two categories (low/high), where median intakes among the controls were used as cut-off points, After adjust ment for major osteoporosis risk factors, the odds ratio (OR) for hip fract ure among current smokers with a low intake of vitamin E was 3.0 (95% confi dence interval 1.6-5.4) and of vitamin C 3.0 (1.6-5.6). In contrast, the OR decreased to 1.1 (0.5-2.4) and 1.4 (0.7-3.0) with high intakes of vitamin E and C, respectively. This effect was not seen for beta-carotene, selenium , calcium, or vitamin B-6, In current smokers with a low intake of both vit amins E and C, the OR increased to 4.9 (2.2-11.0), The influence of the int ake of these two antioxiddant vitamins on hip fracture risk was less pronou nced in former smokers. Our results suggest a role for oxidant stress in th e adverse effects on the skeleton of smoking, and that an insufficient diet ary intake of vitamin E and C may substantially increase the risk of hip fr acture in current smokers, whereas a more adequeate intake seems to be prot ective.