Br J Nutr. 2015 Oct 14;114(7):1099-107. doi: 10.1017/S0007114515002135. Epub 2015 Aug 21.
Egg intake and cancers of the breast, ovary and prostate: a dose-response meta-analysis of prospective observational studies.
Keum N1, Lee DH1, Marchand N1, Oh H1, Liu H2, Aune D3, Greenwood DC4, Giovannucci EL1.
1Department of Nutrition,Harvard T.H. Chan School of Public Health,Boston,USA.
2Department of Epidemiology and Health Statistics,Zhejiang University,Zhejiang,People’s Republic of China.
3Department of Public Health and General Practice,Faculty of Medicine, Norwegian University of Science and Technology,Trondheim,Norway.
4Division of Biostatistics,University of Leeds,Leeds,UK.
Evidence suggests that egg intake may be implicated in the aetiology of sex hormone-related cancers.
However, dose-response relationships between egg intake and such cancers are unclear.
Thus, we conducted a dose-response meta-analysis to summarise the dose-response relationships between egg consumption and the risk of breast, prostate and gynaecological cancers.
A literature search was performed using PubMed and Embase up to April 2015 to identify relevant prospective observational studies. Summary relative risk (RR) and 95% CI were estimated using a random-effects model.
For breast cancer, the linear dose-response meta-analysis found a non-significantly increased risk (RR for an increase of 5 eggs consumed/week: 1·05, 95% CI 0·99, 1·11, n 16,023 cases).
Evidence for non-linearity was not statistically significant (P non-linearity= 0·50, n 15,415 cases) but consuming ≥ 5 eggs/week was significantly associated with an increased risk of breast cancer compared with no egg consumption, with the summary RR being 1·04 (95% CI 1·01, 1·07) for consuming 5 eggs/week and 1·09 (95% CI 1·03, 1·15) for consuming about 9 eggs/week. For other cancers investigated, the summary RR for an increase of 5 eggs consumed/week was 1·09 (95% CI 0·96, 1·24, n 2636 cases) for ovarian cancer; 1·47 (95% CI 1·01, 2·14, n 609 cases) for fatal prostate cancer, with evidence of small-study effects (P Egger= 0·04).
No evidence was found for an association with the risk of total prostate cancer. While our conclusion was tempered by the potential for publication bias and confounding, high egg intake may be associated with a modestly elevated risk of breast cancer, and a positive association between egg intake and ovarian and fatal prostate cancers cannot be ruled out.