Although eggs are lumped into an overall healthier dietary pattern in some prospective studies (chicken, eggs, legumes, nuts), there are other studies suggesting concern around egg consumption and increased cancer risk. For prostate cancer in particular, there are several studies which found an increased risk. According to a prospective study published in Cancer Prevention Research, healthy men who consumed 2.5 or more eggs per week had an 81% increased risk of lethal prostate cancer compared with men who consumed less than 0.5 eggs per week (28). The authors hypothesized that this was due to a high level of cholesterol and choline in the eggs, which are both highly concentrated in prostate cancer cells. In 2012, the authors looked specifically at choline content and found that men in the highest quintile of choline intake (471 mg/day) had a 70% increased risk of lethal prostate cancer (38). Although choline is found in all animal foods it is more highly concentrated in eggs at 250 mg per egg.
A meta-analysis published in 2015 showed a modestly elevated risk for not only prostate cancer but also breast and ovarian cancers for those with the highest intake of eggs, more than 5 per week, as compared to those with no egg consumption at all (39). These authors also suggest that the choline and cholesterol were causative. Choline may increase the proliferation and progression of prostate cancer (1), while cholesterol serves as a pre-cursor for the biosynthesis of sex hormones and a primary metabolite of cholesterol acts as an estrogen receptor agonist in breast cancer cells (39). Another 2015 meta-analysis showed an association between egg consumption and increased risk for ovarian cancer (40). Cohort studies have also shown an association between egg consumption and increased breast cancer risk; especially for post-menopausal women (41). This seemed to be true for those consuming 2-5 eggs/week.