Abstract
Estrogens have a central role in the etiology of endometrial cancer. Milk and dairy products are a source of steroid hormones and growth factors that might have physiological effects in humans. We hypothesized that high intakes of milk and dairy products are associated with an increased risk of endometrial cancer, particularly among postmenopausal women not using hormone therapy. This was a prospective cohort study with 68,019 female participants in the Nurses' Health Study aged 34-59 in 1980. Milk and dairy consumption were assessed in 1980, 1984, 1986, 1990, 1994, 1998 and 2002 as servings per day and the follow-up continued through 2006. The multivariate relative risks (RRs) of adenocarcinoma of the endometrium across categories of cumulatively averaged total dairy consumption compared with < 1 svg/day were: 0.94 (95% CI = 0.71-1.25) for 1-1.4 svg/day, 1.14 (0.87-1.49) for 1.5-1.9 svg/day, 1.10 (0.84-1.44) for 2-2.9 svg/day, 1.26 (0.94-1.70) for ≥ 3 svg/day (p for trend = 0.06). The association between total dairy intake and endometrial cancer was significant only among the postmenopausal women (for ≥ 3 svg/day RR = 1.41, 95% CI = 1.01-1.98, p for trend = 0.02) and was evident only among those who were not currently using hormone therapy (RR = 1.58, 95% CI = 1.05-2.36, p for trend = 0.003). Total dairy intake was not significantly associated with risk of preinvasive endometrial cancer. In conclusion, we observed a marginally significant overall association between dairy intake and endometrial cancer and a stronger association among postmenopausal women who were not using estrogen-containing hormones.