Associations of calcium and dairy product intakes with all-cause, all-cancer, colorectal cancer and CHD mortality among older women in the Iowa Women's Health Study

Abstract

Ca and dairy product intakes may be inversely associated with all-cause and cause-specific mortality, and non-Ca components of dairy products, such as insulin-like growth factor-1, may be independently associated with mortality. We investigated associations of Ca and dairy product intakes with all-cause, all-cancer, colorectal cancer (CRC) and CHD mortality among 35 221 55- to 69-year-old women in the prospective Iowa Women's Health Study, who were cancer-free in 1986. We assessed diet using a Willett FFQ, and associations using multivariable Cox proportional hazards regression. We estimated residuals from linear regression models of dairy products with dietary Ca to investigate total and specific dairy products independent of their Ca content. Through 2012, 18 687 participants died, including 4665 from cancer (including 574 from CRC) and 3603 from CHD. For those in the highest relative to the lowest quintiles of intake, the multivariable-adjusted hazard ratios (HR) and 95 % CI for total Ca (dietary plus supplemental) were 0·88 (0·83, 0·93; P trend=0·001) for all-cause mortality, 0·91 (0·81, 1·02; P trend=0·34) for all-cancer mortality, 0·60 (0·43, 0·83; P trend=0·002) for CRC mortality and 0·73 (0·64, 0·83; P trend <0·0001) for CHD mortality. The corresponding HR for associations of whole milk, whole milk residuals, and low-/non-fat milk residuals with all-cause mortality were 1·20 (95 % CI 1·13, 1·27), 1·20 (95 % CI 1·13, 1·28) and 0·91 (95 % CI 0·86, 0·96), respectively. These results suggest that Ca may be associated with lower risk of all-cause, CRC and CHD mortality, and that non-Ca components of milk may be independently associated with mortality.

Keywords: CRC colorectal cancer; HR hazard ratio; ICD International Classification of Diseases; IGF-1 insulin-like growth factor-1; Calcium; Cohort studies; Colorectal cancer; Dairy products; Mortality.