title: Vitamin A intake and hip fractures among postmenopausal women.
abstract: BACKGROUND
  Ingestion of toxic amounts of vitamin A affects bone remodeling and can have adverse skeletal effects in animals. The possibility has been raised that long-term high vitamin A intake could contribute to fracture risk in humans.
  
  
  OBJECTIVE
  To assess the relationship between high vitamin A intake from foods and supplements and risk of hip fracture among postmenopausal women.
  
  
  METHODS
  Prospective analysis begun in 1980 with 18 years of follow-up within the Nurses' Health Study.
  
  
  METHODS
  General community of registered nurses within 11 US states.
  
  
  METHODS
  A total of 72 337 postmenopausal women aged 34 to 77 years.
  
  
  METHODS
  Incident hip fractures resulting from low or moderate trauma, analyzed by quintiles of vitamin A intake and by use of multivitamins and vitamin A supplements, assessed at baseline and updated during follow-up.
  
  
  RESULTS
  From 1980 to 1998, 603 incident hip fractures resulting from low or moderate trauma were identified. After controlling for confounding factors, women in the highest quintile of total vitamin A intake (>/=3000 microgram/d of retinol equivalents [RE]) had a significantly elevated relative risk (RR) of hip fracture (RR, 1.48; 95% confidence interval [CI], 1.05-2.07; P for trend =.003) compared with women in the lowest quintile of intake (<1250 microgram/d of RE). This increased risk was attributable primarily to retinol (RR, 1.89; 95% CI, 1.33-2.68; P for trend <.001 comparing >/=2000 microgram/d vs <500 microgram/d). The association of high retinol intake with hip fracture was attenuated among women using postmenopausal estrogens. Beta carotene did not contribute significantly to fracture risk (RR, 1.22; 95% CI, 0.90-1.66; P for trend =.10 comparing >/=6300 microgram/d vs <2550 microgram/d). Women currently taking a specific vitamin A supplement had a nonsignificant 40% increased risk of hip fracture (RR, 1.40; 95% CI, 0.99-1.99) compared with those not taking that supplement, and, among women not taking supplemental vitamin A, retinol from food was significantly associated with fracture risk (RR, 1.69; 95% CI, 1.05-2.74; P for trend =.05 comparing >/=1000 microgram/d vs <400 microgram/d).
  
  
  CONCLUSIONS
  Long-term intake of a diet high in retinol may promote the development of osteoporotic hip fractures in women. The amounts of retinol in fortified foods and vitamin supplements may need to be reassessed.
authors.affiliation: Channing Laboratory, 181 Longwood Ave, Boston, MA 02115. diane.feskanich@channing.harvard.edu
authors.forename: Diane
authors.initials: D
authors.lastname: Feskanich
authors.forename: Vishwa
authors.initials: V
authors.lastname: Singh
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.forename: Graham A
authors.initials: GA
authors.lastname: Colditz
mesh_terms: D000328:Adult; D000368:Aged; D019587:Dietary Supplements / Q000009:adverse effects; D005260:Female; D006620:Hip Fractures / Q000453:epidemiology*; D006801:Humans; D008875:Middle Aged; D015596:Nutrition Assessment; D010024:Osteoporosis / Q000453:epidemiology; D017698:Postmenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D014801:Vitamin A / Q000008:administration & dosage / Q000009:adverse effects; D019207:beta Carotene
chemical_list: D019207:beta Carotene; D014801:Vitamin A