Closer look at egg studies

“Eating one egg per day increases your risk of diabetes by 60%” reported major news outlet drawing thousands of sharply divided comments.  Before we jump to emotional response (that title like this generates), let’s look at the actual study that created this media sensation. 

The actual result of this study is “Australian researchers who studied a sample of 8,545 Chinese adults found a positive correlation between higher egg consumption and high blood sugar levels.”  “For the study, Dr. Li and her team analyzed data on the 8,545 adults who attended the China Health and Nutrition Survey from 1991 to 2009. China Health and Nutrition Survey is an ongoing survey backed by the US government’s Center for Disease Control and Prevention (CCDC) that aims to examine the effects of the health policies and nutrition in China.” Researchers found that eating 1 egg daily for long time increased risk of developing diabetes by 60%.  The problem with this study is rather simple.  Correlational non-controlled studies have several major weaknesses . They do not account for possible other variables that can and often do bias the results. 

For example, if most of this egg consumption was related to shift from traditional high fruits and vegetables diet to highly processed, often fast food, type of a diet, the higher risk developing diabetes could have been related to eating other foods but not eggs! In biostatistics we often say – correlation is not causation!  

To further discuss this topic, let’s look at 2 prior studies:

First, a 2019 study conducted at a university in Finland showed that eating one egg a day may lower risk of type 2 Diabetes. In this study researches looked at different lipid profiles and found that those men who ate egg daily had a type of profile that is common among men who never develop diabetes.  

Second, a 2009 study found “egg consumption and risk of Type 2 diabetes in men and women”. This prospective study analyzed data from 2 large randomized trials Physicians Health Study. One with over 20k men and Women’s Health Study with over 36k women.  Egg consumption was assessed via questionnaires, with an average follow up of 20 years. Only consumption of over 7 eggs/week was associated with increased risk of diabetes but there was a general trend.  Study conclusion was that confirmation studies are warranted. Authors of this study stated that “in animal experiments, a diet rich in fat has been shown to induce hyperglycemia and hyperinsulinemia.  In addition, a diet enriched in with egg yolk was associated with elevated plasma glucose compared with a control diet in rats. ”  This second study findings are similar to the one Dr. Li and her team published recently.

What is fascinating is that we have rather clear data that ketogenic diets have been shown to not only decrease hyperglycemia and hyperinsulinemia but cure diabetes.  And thinking from very simple biochemical perspective consuming protein vs carbohydrates should have less effect on increasing insulin thus completely negating above study statement. 

Regardless of which camp you believe this recent “anti-egg hype” is coming from it is unlikely to change believers opinions but it adds to the science.  The best possible explanation that in my mind can offer some reasonable mechanism to explain how eggs indeed may increase risk of diabetes is through an impact on gut microbiome.  We do know that imbalance of gut microbiome is one of key risk factors for diabetes type 2, it is possible that eggs can have negative impact there but much more information is needed to understand the actual science of this effect.
However, more controlled studies is needed to clarify this specific point.

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