Purpose: Previous epidemiological studies on egg consumption and the risk of gastrointestinal (GI) neoplasms suggest a positive association; however, data are limited and the evidence remains controversial. This study aims to investigate and quantify the potential dose-response relationship with an evaluation of cancer site-specific differences.
Methods: Relevant studies were identified after the literature search via electronic databases until January 2014. Subgroup analysis for serving portions was performed using two standardized classification methods: (1) less than 3, or 3 or more eggs per week; (2) less than 3, 3-5, or more than 5 eggs per week. Method two excludes studies that only reported consumption frequency. Pooled adjusted odds ratios (ORs) comparing highest and lowest categories of dietary pattern scores were calculated using a random-effects model.
Results: Thirty-seven case-control and seven cohort studies were included for meta-analysis, which contained a total of 424,867 participants and 18,852 GI neoplasm cases. The combined odds ratio (OR) was calculated to 1.15 (95% CI 1.09-1.22; p value heterogeneity <0.001), showing only a slight increase in risk. The correlation was stronger for colon cancers 1.29 (95% CI 1.14-1.46; p value heterogeneity <0.22). Dose-response analysis revealed similar results with stratification methods, and the ORs for an intake of <3 and ≥3 eggs per week were 1.14 (95% CI 1.07-1.22; p value heterogeneity = 0.38) and 1.25 (95% CI 1.14-1.38; p value heterogeneity = 0.25), respectively. With method 2, the ORs for an intake of <3, 3-5, and >5 eggs per week were 1.13 (95% CI 1.06-1.21; p value heterogeneity = 0.25), 1.14 (95% CI 1.01-1.29; p value heterogeneity = 0.06), and 1.19 (95% CI 1.01-1.39; p value heterogeneity <0.001), respectively.
Conclusion: This study provides evidence that egg consumption is associated with a positive dose-response association with the development of GI neoplasms.