title: Dietary calcium intake and risk of fracture and osteoporosis: prospective longitudinal cohort study.
abstract: OBJECTIVE
  To investigate associations between long term dietary intake of calcium and risk of fracture of any type, hip fractures, and osteoporosis.
  
  
  METHODS
  A longitudinal and prospective cohort study, based on the Swedish Mammography Cohort, including a subcohort, the Swedish Mammography Cohort Clinical.
  
  
  METHODS
  A population based cohort in Sweden established in 1987.
  
  
  METHODS
  61,433 women (born between 1914 and 1948) were followed up for 19 years. 5022 of these women participated in the subcohort.
  
  
  METHODS
  Primary outcome measures were incident fractures of any type and hip fractures, which were identified from registry data. Secondary outcome was osteoporosis diagnosed by dual energy x ray absorptiometry in the subcohort. Diet was assessed by repeated food frequency questionnaires.
  
  
  RESULTS
  During follow-up, 14,738 women (24%) experienced a first fracture of any type and among them 3871 (6%) a first hip fracture. Of the 5022 women in the subcohort, 1012 (20%) were measured as osteoporotic. The risk patterns with dietary calcium were non-linear. The crude rate of a first fracture of any type was 17.2/1000 person years at risk in the lowest quintile of calcium intake, and 14.0/1000 person years at risk in the third quintile, corresponding to a multivariable adjusted hazard ratio of 1.18 (95% confidence interval 1.12 to 1.25). The hazard ratio for a first hip fracture was 1.29 (1.17 to 1.43) and the odds ratio for osteoporosis was 1.47 (1.09 to 2.00). With a low vitamin D intake, the rate of fracture in the first calcium quintile was more pronounced. The highest quintile of calcium intake did not further reduce the risk of fractures of any type, or of osteoporosis, but was associated with a higher rate of hip fracture, hazard ratio 1.19 (1.06 to 1.32).
  
  
  CONCLUSIONS
  Gradual increases in dietary calcium intake above the first quintile in our female population were not associated with further reductions in fracture risk or osteoporosis.
authors: Department of Surgical Sciences, Section of Orthopaedics, Uppsala University, Uppsala, Sweden. eva.warensjo@surgsci.uu.se
authors: Eva
authors: E
authors: Warensjö
authors: Liisa
authors: L
authors: Byberg
authors: Håkan
authors: H
authors: Melhus
authors: Rolf
authors: R
authors: Gedeborg
authors: Hans
authors: H
authors: Mallmin
authors: Alicja
authors: A
authors: Wolk
authors: Karl
authors: K
authors: Michaëlsson
references: J Bone Miner Res. 2009 May;24(5):935-42
references: 19113911
references: J Intern Med. 2009 Nov;266(5):476-83
references: 19570054
references: PLoS One. 2009 Nov 13;4(11):e7747
references: 19915719
references: Epidemiology. 2008 Nov;19(6):860-7
references: 18938655
references: Lancet. 1996 Mar 2;347(9001):587-94
references: 8596324
references: BMJ. 1989 Jan 28;298(6668):205-8
references: 2493864
references: Osteoporos Int. 1994 Nov;4(6):368-81
references: 7696835
references: J Chronic Dis. 1987;40(5):373-83
references: 3558716
references: Am J Epidemiol. 1999 Mar 15;149(6):531-40
references: 10084242
references: BMJ. 2010 Jul 29;341:c3691
references: 20671013
references: Br J Nutr. 2004 Apr;91(4):625-34
references: 15035690
references: J Nutr. 2004 Jul;134(7):1800-5
references: 15226472
references: Eur J Epidemiol. 2008;23(10):661-7
references: 18704705
references: Am J Clin Nutr. 1997 Apr;65(4 Suppl):1220S-1228S; discussion 1229S-1231S
references: 9094926
references: Bone. 2003 Jun;32(6):694-703
references: 12810177
references: J Am Diet Assoc. 1998 Jun;98(6):699-706
references: 9627630
references: Ann N Y Acad Sci. 2010 Mar;1192:45-56
references: 20392217
references: Osteoporos Int. 2008 Aug;19(8):1119-23
references: 18286218
references: Public Health Nutr. 2007 Nov;10(11):1314-20
references: 17381900
references: Eur J Cancer. 2009 Nov;45(17):3042-6
references: 19464165
references: Am J Clin Nutr. 2003 Feb;77(2):504-11
references: 12540414
references: J Nutr. 2007 Nov;137(11 Suppl):2507S-2512S
references: 17951494
references: Public Health Nutr. 2002 Dec;5(6A):969-76
references: 12638598
references: Stat Med. 1997 Apr 30;16(8):901-10
references: 9160487
references: J Clin Endocrinol Metab. 2010 Jun;95(6):2637-45
references: 20332246
references: Am J Epidemiol. 1997 May 15;145(10):926-34
references: 9149664
references: Am J Clin Nutr. 2007 Nov;86(5):1399-404
references: 17991652
references: Public Health Nutr. 2004 Feb;7(1A):227-43
references: 14972062
references: Am J Clin Nutr. 2009 Jan;89(1):277-82
references: 19056569
references: Am J Clin Nutr. 2009 Sep;90(3):556-60
references: 19491389
references: Br J Nutr. 2009 Dec;102 Suppl 1:S38-55
references: 20100367
references: JAMA. 2009 Oct 21;302(15):1666-73
references: 19843901
references: Med Care. 2005 Nov;43(11):1130-9
references: 16224307
references: Am J Clin Nutr. 2007 Dec;86(6):1780-90
references: 18065599
references: Lancet. 2007 Aug 25;370(9588):657-66
references: 17720017
references: J Bone Miner Res. 1997 Sep;12(9):1321-9
references: 9286747
references: Am J Med. 2006 Sep;119(9):777-85
references: 16945613