Vitamin A intake and the risk of hip fracture in postmenopausal women: the Iowa Women?s Health Study

Abstract

Excessive intake of vitamin A is postulated to have a detrimental effect on bone by inducing osteoporosis. This may lead to an increased risk of fracture, particularly in persons who are already at risk of osteoporosis. However, few studies have specifically examined the association of vitamin A intake through diet and supplement use, with fractures in a cohort of older, community-dwelling women. We prospectively followed a cohort of 34,703 postmenopausal women from the Iowa Women's Health Study to determine if high levels of vitamin A and retinol intake through food and supplement use were associated with an increased risk of hip or all fractures. A semiquantitative food frequency questionnaire was used to obtain the participants' baseline vitamin A and retinol intake. Participants were followed for a mean duration of 9.5 years for incident self-reported hip and nonhip fractures. After multivariate adjustment, it was revealed that users of supplements containing vitamin A had a 1.18-fold increased risk of incident hip fracture (n = 525) compared with nonusers (95% CI, 0.99 to 1.41), but there was no evidence of an increased risk of all fractures (n = 6,502) among supplement users. There was also no evidence of a dose-response relationship in hip fracture risk with increasing amounts of vitamin A or retinol from supplements. Furthermore, our results showed no association between vitamin A or retinol intake from food and supplements, or food only, and the risk of hip or all fractures. In conclusion, we found little evidence of an increased risk of hip or all fractures with higher intakes of vitamin A or retinol among a cohort of older, postmenopausal women.

Significance of Vitamin A (Retinol) in Ageing

“…According to multivariate analysis of data, retinol intake was negatively associated with BMD. According to a cox regression analysis the risk of fracture was found to be the highest among men with the highest levels of serum retinol in a population-based (2322 men, 49-51 years) longitudinal cohort study [22]. These results are consistent with the results reported from animal and epidemiologic dietary studies.…”

Vitamins, Are They Safe?

“…It was shown that risk of hip fracture was 1.18 fold in vitamin A supplement users compared to nonusers (95% CI, 0.99 to 1.41), but there was not a greater risk of all fractures among the users of vitamin A supplement. 70 The importance of vitamin A in the bone remodeling process has been shown in various studies. Vitamin A deficiency results in retarded bone growth, but in the other hand hypervitaminosis A leads to accelerated bone resorption, bone fragility, and spontaneous fracture.…”

Serum Retinoids and β-Carotene as Predictors of Hip and Other Fractures in Elderly Women

“…(1)(2)(3)(4)(5)(6)(7)(8)(9)(10) Numerous case studies have shown that overt vitamin A toxicity is associated with increased bone resorption and hypercalcemia. (11)(12)(13) Some studies have found that higher dietary vitamin A intake may account for a component of fracture risk within the general population and that supplemental vitamin A may be harmful even within recommended limits.…”

“…In marked contrast, two recent prospective studies found no association between dietary vitamin A intake and risk of fracture. (5,6) Only one prospective study (4) has addressed exposure to vitamin A using biochemical markers of retinol intake in relation to fracture risk. This cohort study (4) followed 2322 middle-aged Swedish men for 20 years and reported a 64% increase in risk of any osteoporotic fracture for men in the top quintile of serum retinol relative to those in the middle quintile.…”