High- and Low-fat Dairy Intake, Recurrence, and Mortality After Breast Cancer Diagnosis

Candyce H. Kroenke; Marilyn L. Kwan; Carol Sweeney; Adrienne Castillo; Bette J. Caan

Disclosures

J Natl Cancer Inst. 2013;105(9):616-623. 

In This Article

Results

Study participants contributed 21 273 person-years of follow-up. Follow-up ranged from 1.8 to 14.7 years, with a median of 11.8 years.

Women who consumed the greatest amount of high-fat dairy had higher levels of physical activity, lower alcohol intake, higher body mass index, and were less likely to be never-smokers. They also had higher fiber and red meat intake and, as expected, higher consumption of nutrients found within dairy. Disease characteristics were unrelated to high-fat dairy intake. Consumption of high-fat dairy was unrelated to reproductive factors (Table 1).

Consumption of High- and Low-fat Dairy Intake

Consumption of dairy intake was relatively limited (median = 1.4 servings/day) (Table 2). Women reported the largest intake of low-fat milk and butter and relatively limited consumption of low-fat dairy dessert, low-fat cheese, and high-fat yogurt. Overall, low-fat dairy intake (median = 0.7 servings/day) was greater than high-fat dairy intake (median = 0.5 servings/day).

Dairy Intake and Breast Cancer Outcomes

In minimally adjusted analyses, we found no statistically significant associations between overall dairy intake and outcomes, although dairy intake was positively related to overall mortality in multivariate-adjusted analyses (Table 3). Low-fat dairy intake was inversely related to all-cause mortality in minimally adjusted analyses, but it was unrelated to outcomes in multivariable- adjusted analyses (P > 0.05, all associations). By contrast, in minimally and multivariable-adjusted results, high-fat dairy intake was positively related to mortality outcomes. In multivariable- adjusted analyses, compared with the reference (0 to <0.5 servings/day), those consuming larger amounts of high-fat dairy had higher breast cancer mortality (0.5–1.0 servings/day: hazard ratio [HR] =1.20, 95% confidence interval [CI] = 0.82 to 1.77; >1.0 servings/day: HR = 1.49, 95% CI = 1.00 to 2.24; P trend = .05), higher all-cause mortality (P trend < 0.001), and higher non–breast cancer mortality (P trend = 0.007). There was a suggestion of an increased risk of recurrence with 1 or more servings per day of high-fat dairy intake, but the association was not statistically significant (Table 4). Associations with diet assessed as the updated cumulative average were virtually identical to those in Table 3 and Table 4 (data not shown). Tests of proportionality were not statistically significant.

Adjustment for nutrients within dairy, including calcium, vitamin D, and potassium, had little effect on associations. However, high-fat dairy and saturated fat intake were sufficiently correlated (r = 0.70; P < .001) that we were unable to evaluate independent associations.

We attempted to evaluate whether particular dairy foods explained the association between high-fat dairy intake and outcomes. We had limited power to examine these associations, but results suggested that overall associations were not attributable to one or two specific foods (data not shown).

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