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What Came First, Diabetes or the Egg?

Despite multiple studies on the topic, it’s still unclear whether eggs increase type 2 diabetes risk.

There are many nutritional and economic benefits associated with the consumption of eggs. They are a low-cost source of vitamins and protein for many people. However, previous observational studies have pointed to the possibility that they may increase the risk of developing type 2 diabetes.

A recent meta-analysis of prospective cohort studies published prior to October 2015 was undertaken to shed some light on this issue. The literature search was restricted to articles written in English and conducted in humans, and was gathered through a search of OVID, Cochrane, Google Scholar and PubMed databases. Close to 2,000 studies were identified, but 1,147 were excluded due to lack of access to original or full text articles. A detailed manual review of titles and abstracts narrowed down the literature search to twelve prospective cohorts pulled from 8 individual studies.  Seven of the cohorts were conducted within the United States. Publication bias was measured and elimination of one study at a time was performed during result analysis to evaluate the presence of influential studies.

A total of 219,979 participants from around the world were included in analysis, 8,911 of which developed diabetes as defined mostly by ADA criteria (fasting glucose >126 mg/dL, non-fasting glucose >200 mg/dL, or hemoglobin A1c >6.5%). Mean patient ages across all 12 cohorts ranged from 38.5 to 73.2 years, and participants were followed over a range of 5 to 20 years.  Food frequency questionnaires (some of these self-administered) and journal records were used to assess patient diets. The primary outcome analyzed the relative risk (RR) of developing diabetes with the consumption of eggs. A P-value of <0.05 was considered significant.

It was found that the overall relative risk associated with egg intake was 1.09 (95% confidence interval (CI): 0.99, 1.20). However, when stratifying the data according to geographic location and looking at only U.S. studies, it was found that there was a 39% increased risk of developing diabetes with high egg consumption compared with low egg consumption (RR = 1.39; 95% CI: 1.21, 1.60). Additionally, there appears to be no additive risk associated with egg consumption in studies done outside of the United States (RR = 0.89; 95% CI: 0.79, 1.02). Secondary analysis of egg consumption across all studies showed that consuming less than 3 eggs per week was not associated with a risk of DM. However, an elevated risk was noted with consumption of 3 or more eggs in a week for U.S. participants only. No evidence of influential studies or publication bias was found upon review, and there appeared to be heterogeneity across the 12 prospective cohorts (I2 = 73.6%; P < 0.001).

According to this worldwide meta-analysis, there is no connection between sporadic egg consumption and the development of diabetes. When consumption increases to 3 or more eggs per week, the risk of diabetes increases, but only in the United States. These findings raise more questions as to whether frequent egg ingestion is associated with other dietary factors and poor food choices available to Americans that may foster the risk for diabetes.

Practice Pearls:

  • Enjoy eggs in moderation to avoid increasing the risk of developing diabetes.
  • Limit egg consumption to less than 3 eggs per week.
  • Additional dietary choices of Americans, not controlled for this study, may differ from that of Europeans, which may have introduced a confounding factor independent of egg consumption.

Researched and prepared by Devon Brooks,  Doctor of Pharmacy Candidate LECOM College of  Pharmacy, reviewed by Dave Joffe, BSPharm, CDE

Djousse L, Khawaja OA, Gaziano JM. “Egg consumption and risk of type 2 diabetes: a meta-analysis of prospective studies.” American Journal of Clinical Nutrition. 103.2 (2016): 474-80. Print.