The present prospective study was designed to investigate the association between meat, egg, and dairy product consumption and risk of breast cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) study cohort. Information concerning diet was collected from 319,826 women during the period 1992 - 2003. During a median follow-up period of 8.8 years, 7,119 breast cancer cases were diagnosed. Multivariate Cox proportional hazard models were used to calculate disease hazard ratios. No consistent overall association was found between risk of breast cancer and consumption of any of the food groups under study. High consumption of processed meat was associated with a modest increase in breast cancer risk in the categorical model (hazard ratio: 1.10; 95% CI: 1.00 - 1.20; highest versus with lowest quintile: P for trend = 0.07). An association of breast cancer risk with butter consumption for premenopausal women was suggested in subgroup analysis (hazard ratio: 1.28; 95% CI: 1.06 - 1.53; highest compared with lowest quintile: P for trend = 0.21). Between-country heterogeneity was found for red meat consumption (Q statistic = 18.03; P = 0.05) and was significantly explained by the proportion of meat cooked at high temperature (P = 0.023). The authors conclude that they had not consistently identified intakes of meat, eggs, or dairy products as risk factors for breast cancer.

The current case-control study was designed to determine the associations between diet in early life and the risk of breast cancer in adulthood. The study was conducted among participants in the Nurses' Health Study who completed a questionnaire about their diets during high school. 843 eligible cases were matched with controls on the basis of age. It was found that women who had consumed more eggs, vegetable fat and fiber during high school had a lower risk of breast cancer. Women who consumed more butter had a higher risk.

Conjugated linoleic acid (CLA), which is present in milk and meat from ruminants, has been shown to have anticarcinogenic activity against breast cancer in animal and in vitro experiments. The present study was designed to evaluated the association between intakes of CLA and other fatty acids and the risk of breast cancer in the Netherlands Cohort Study. Information obtained by means of a validated 150-item food-frequency questionnaire was linked to an existing database with information on specific fatty acids in European foods. There were 941 new cases of breast cancer during a follow-up period of 6.3 years. Associations were calculated for energy-adjusted intakes of fatty acids and CLA-containing food groups (e.g., butter, cheese, milk, other milk products, and meat). CLA intake was found to have a weak, positive association with breast cancer incidence (rate ratio for highest compared with lowest quintile: 1.24, 95% CI: 0.91, 1.69; P for trend = 0.02). Statistically significant positive associations also were found with total trans fatty acids and with saturated fatty acids (borderline). Significant inverse relations were found with monounsaturated and cis-unsaturated fatty acids, whereas the total fat and energy intake of CLA-containing food groups were found not to be related to breast cancer incidence. The authors conclude that the apparent anticarcinogenic properties of CLA in animal and tissue culture models was not confirmed in this epidemiological study of humans.

Here, the effects of diet and body weight in 472 women diagnosed with early-stage breast cancer during 1982 to 1984 were studied with respect to eventual breast cancer recurrence and death. The most powerful effects were observed in premenopausal women. It was found that increasing consumption of butter, margarine, and lard (risk ratio (RR)=1.67; 95% confidence interval (CI)=1.17–2.39) and beer (RR=1.58; CI=1.15–2.17) increased the risk of recurrence, after accounting for disease stage and age. An increased risk of recurrence was also found for consumption of red meat, liver, and bacon, corresponding to approximately a doubling of risk for each number of times per day that foods in this category were consumed (RR=1.93; CI=0.89–4.15). Body weight also increased risk at the rate of 9% (RR=1.09; CI=1.02–1.17) for each kg/m2 (equivalent to about 5.8 pounds for a woman 54 inches tall). For risk of death, the results were similar, but relative body weight was more strongly correlated, increasing risk by 12% per kg/m2 (RR=1.12; CI=1.03–1.22).