Egg intake and cancers of the breast, ovary and prostate: a dose–response meta-analysis of prospective observational studies

Abstract

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 ¼ 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 ¼ 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.

Dietary Protein Sources and Incidence of Breast Cancer: A Dose-Response Meta-Analysis of Prospective Studies

“…Additionally, this is an updated meta-analysis to investigate the association between total red meat, fresh red meat, processed meat, fish, egg, soy food, and total milk intake and incidence of breast cancer. Although some previous meta-analyses [15,74,75,76,77] have investigated the association between total red meat, fresh red meat, processed meat, fish, egg, soy food, and total milk intake and incidence of breast cancer, many of them were based on highest versus lowest intake. Since then, a number of large-scale prospective studies were performed.…”

“…Third, different studies used different units (such as servings and times). Although we converted these units into grams per day according to standard conversions from the Food Standards Agency [13] and other documents [14,15,16], this could still influence the association.…”

“…Then, we performed a dose-response analysis with the method proposed by Greenland and Longnecker [12] to compute linear trends and 95% CIs from the natural logs of the RRs and CIs across categories of each source of protein intake. When the included studies used different units (such as servings and times), we converted them into grams per day according to standard conversions from the Food Standards Agency [13] and other documents [14,15,16] (for fresh red meat, poultry, and fish, one serving was equivalent to 120 g; for egg and processed meat, one serving was equal to 50 g; for dairy products, the weight of one serving was 200 g; for nuts, it was 28 g). For soy foods and nuts, we used serving/day as units, because most studies used servings as units.…”

Nutrimetabolomics: An Integrative Action for Metabolomic Analyses in Human Nutritional Studies

“…Observational studies help generating hypotheses and exploring associations between diet and health outcomes. These studies, however, cannot categorically prove cause‐and‐effect relationships . Interventional study designs can vary from short‐term studies, when the immediate effect of the intervention is investigated within few hours to as long as 24 or 48 h postprandial (i.e., meal/food item consumed once), to long‐term studies that evaluate the effects of the intervention over a period of weeks, months, or years .…”

Nutrition, Cancer Genetics and Epigenetics

“…In contrast, an increased risk of estrogen receptor-negative breast cancer was observed in women who were committed to a diet high in grains, dairy, and sugar and low in vegetables and fish [30]. A dose-response meta-analysis investigating the relationship between egg consumption and the risk of breast, prostate, and ovarian cancers revealed non-significant increase in breast cancer risk, although it was suggested that a positive association between egg intake and fatal prostate and ovarian cancers with an increase in egg consumption to five eggs per week could not be ruled out [31]. Furthermore, the association between dietary fiber intake and the risk of ovarian cancer was observed in a meta-analysis of 19 studies involving 567,742 participants [32].…”