Background: More than 20 studies have investigated the relation between meat and dairy food consumption and breast cancer risk with conflicting results. Our objective was to evaluate the risk of breast cancer associated with meat and dairy food consumption and to assess whether non-dietary risk factors modify the relation.
Methods: We combined the primary data from eight prospective cohort studies from North America and Western Europe with at least 200 incident breast cancer cases, assessment of usual food and nutrient intakes, and a validation study of the dietary assessment instrument. The pooled database included 351,041 women, 7379 of whom were diagnosed with invasive breast cancer during up to 15 years of follow-up.
Results: We found no significant association between intakes of total meat, red meat, white meat, total dairy fluids, or total dairy solids and breast cancer risk. Categorical analyses suggested a J-shaped association for egg consumption where, compared to women who did not eat eggs, breast cancer risk was slightly decreased among women who consumed < 2 eggs per week but slightly increased among women who consumed > or = 1 egg per day.
Conclusions: We found no significant associations between intake of meat or dairy products and risk of breast cancer. An inconsistent relation between egg consumption and risk of breast cancer merits further investigation.