Vitamin A and retinol intakes and the risk of fractures among participants of the Women's Health Initiative Observational Study.
BACKGROUND
Excessive intakes of vitamin A have been shown to have adverse skeletal effects in animals. High vitamin A intake may lead to an increased risk of fracture in humans.


OBJECTIVE
The objective was to evaluate the relation between total vitamin A and retinol intakes and the risk of incident total and hip fracture in postmenopausal women.


METHODS
A total of 75,747 women from the Women's Health Initiative Observational Study participated. The risk of hip and total fractures was determined using Cox proportional hazards models according to different intakes of vitamin A and retinol.


RESULTS
In the analysis adjusted for some covariates (age; protein, vitamin D, vitamin K, calcium, caffeine, and alcohol intakes; body mass index; hormone therapy use; smoking; metabolic equivalents hours per week; ethnicity; and region of clinical center), the association between vitamin A intake and the risk of fracture was not statistically significant. Analyses for retinol showed similar trends. When the interaction term was analyzed as categorical, the highest intake of retinol with vitamin D was significant (P = 0.033). Women with lower vitamin D intake (< or =11 microg/d) in the highest quintile of intake of both vitamin A (hazard ratio: 1.19; 95% CI: 1.04, 1.37; P for trend: 0.022) and retinol (hazard ratio: 1.15; 95% CI: 1.03, 1.29; P for trend: 0.056) had a modest increased risk of total fracture.


CONCLUSIONS
No association between vitamin A or retinol intake and the risk of hip or total fractures was observed in postmenopausal women. Only a modest increase in total fracture risk with high vitamin A and retinol intakes was observed in the low vitamin D-intake group.
Caire-Juvera
Graciela
G
Nutrition Department, Centro de Investigación en Alimentación y Desarrollo, Hermosillo, Sonora, Mexico. gcaire@ciad.mx
Ritenbaugh
Cheryl
C
Wactawski-Wende
Jean
J
Snetselaar
Linda G
LG
Chen
Zhao
Z
D000368:Aged; D000428:Alcohol Drinking; D015992:Body Mass Index; D002110:Caffeine / Q000008:administration & dosage; D002136:Calcium, Dietary / Q000008:administration & dosage; D015331:Cohort Studies; D004044:Dietary Proteins / Q000008:administration & dosage; D015914:Estrogen Replacement Therapy; D005260:Female; D050723:Fractures, Bone / Q000453:epidemiology*; D006620:Hip Fractures / Q000453:epidemiology*; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000453:epidemiology; D017698:Postmenopause; D016016:Proportional Hazards Models; D012307:Risk Factors; D012907:Smoking; D014801:Vitamin A / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives; D014807:Vitamin D / Q000008:administration & dosage; D014812:Vitamin K / Q000008:administration & dosage
D002136:Calcium, Dietary; D004044:Dietary Proteins; D014801:Vitamin A; D014812:Vitamin K; D014807:Vitamin D; D002110:Caffeine