Dairy foods, calcium, and colorectal cancer: a pooled analysis of 10 cohort studies.
BACKGROUND
Studies in animals have suggested that calcium may reduce the risk of colorectal cancer. However, results from epidemiologic studies of intake of calcium or dairy foods and colorectal cancer risk have been inconclusive.


METHODS
We pooled the primary data from 10 cohort studies in five countries that assessed usual dietary intake by using a validated food frequency questionnaire at baseline. For most studies, follow-up was extended beyond that in the original publication. The studies included 534 536 individuals, among whom 4992 incident cases of colorectal cancer were diagnosed between 6 and 16 years of follow-up. Pooled multivariable relative risks for categories of milk intake and quintiles of calcium intake and 95% confidence intervals (CIs) were calculated. All statistical tests were two-sided.


RESULTS
Milk intake was related to a reduced risk of colorectal cancer. Compared with the lowest category of intake (<70 g/day), relative risks of colorectal cancer for increasing categories (70-174, 175-249, and > or =250 g/day) of milk intake were 0.94 (95% CI = 0.86 to 1.02), 0.88 (95% CI = 0.81 to 0.96), and 0.85 (95% CI = 0.78 to 0.94), respectively (P(trend)<.001). Calcium intake was also inversely related to the risk of colorectal cancer. The relative risk for the highest versus the lowest quintile of intake was 0.86 (95% CI = 0.78 to 0.95; P(trend) =.02) for dietary calcium and 0.78 (95% CI = 0.69 to 0.88; P(trend)<.001) for total calcium (combining dietary and supplemental sources). These results were consistent across studies and sex. The inverse association for milk was limited to cancers of the distal colon (P(trend)<.001) and rectum (P(trend) =.02).


CONCLUSIONS
Higher consumption of milk and calcium is associated with a lower risk of colorectal cancer.
Cho
Eunyoung
E
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. eunyoung.cho@channing.harvard.edu
Smith-Warner
Stephanie A
SA
Spiegelman
Donna
D
Beeson
W Lawrence
WL
van den Brandt
Piet A
PA
Colditz
Graham A
GA
Folsom
Aaron R
AR
Fraser
Gary E
GE
Freudenheim
Jo L
JL
Giovannucci
Edward
E
Goldbohm
R Alexandra
RA
Graham
Saxon
S
Miller
Anthony B
AB
Pietinen
Pirjo
P
Potter
John D
JD
Rohan
Thomas E
TE
Terry
Paul
P
Toniolo
Paolo
P
Virtanen
Mikko J
MJ
Willett
Walter C
WC
Wolk
Alicja
A
Wu
Kana
K
Yaun
Shiaw-Shyuan
SS
Zeleniuch-Jacquotte
Anne
A
Hunter
David J
DJ
D000236:Adenoma / Q000453:epidemiology / Q000517:prevention & control; D000328:Adult; D000368:Aged; D000818:Animals; D002136:Calcium, Dietary / Q000008:administration & dosage*; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control*; D003611:Dairy Products / Q000706:statistics & numerical data*; D004435:Eating; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008892:Milk; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012107:Research Design; D018570:Risk Assessment; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology
D002136:Calcium, Dietary