Up to an Egg a Day May Ward Off Diabetes: Metabolomic Study

Marlene Busko  

January 15, 2019

New research digs down into why middle-aged Finnish men who ate up to one egg a day (high intake) had a lower risk of developing type 2 diabetes than their peers who ate fewer eggs.

The scientists previously showed that in the prospective, population-based Kuopio Ischemic Heart Disease Risk Factor (KIHD) study of middle-aged men in Finland, those in the highest quartile of egg intake (about 1 egg/day) had a 38% lower risk of type 2 diabetes than men in the lowest quartile (about 1 egg/week).  

Now a technique called "nontargeted metabolomics" enables a broad profiling of chemicals and reveals that men who developed type 2 diabetes had higher baseline serum levels of tyrosine and an unknown hexose-containing compound, regardless of egg intake, say early stage researcher Stefania Noerman, MSc, of the University of Eastern Finland, Kuopio, and colleagues, who report their new work in Molecular Nutrition and Food Research.

Although it is too early to draw causal conclusions from this study, "We now have some hints about certain egg-related compounds that may have a role in type 2 diabetes development," Noerman and senior researcher Jyrki Virtanen, PhD, assistant professor of nutritional epidemiology at the same university, explained in an email to Medscape Medical News.

The findings suggest that "moderate consumption of eggs (up to 1 per day for most people) [can be] part of a healthy dietary pattern and healthy lifestyle [for] preventive action against type 2 diabetes," they add.

Invited to comment, Charles P. Vega, MD, health sciences clinical professor, Family Medicine, University of California, Irvine, said: "There are conflicting data regarding how eggs influence the risk of diabetes, but what is clear in clinical practice is that there are much more salient negative lifestyle habits to target to reduce not only the risk of diabetes but improve the risk of cardiovascular disease overall."

"In the constant negotiation with patients regarding diet," he said in an email to Medscape Medical News, "it seems worthwhile to consider trading an egg here or there for the donut or latest bacon-loaded, maple-enhanced, gravy-filled monstrosity being advertised from a fast food chain."

What Is it About Eggs That May Lower Diabetes Risk?

Egg consumption remains controversial, with mainly US studies reporting that high egg consumption is linked with a higher risk of diabetes, Noerman and colleagues write, in contrast to other studies reporting the opposite or null findings, including their own from the KIHD study.

The US studies may not have fully adjusted for higher intake of meat, higher body mass index (BMI), higher rate of smoking, or lower physical activity in people with a high intake of eggs, they suggest.   

Of note, they write, "eggs are an especially rich source of several bioactive compounds, such as carotenoids and choline, which have been shown to have beneficial effects on, for example, insulin resistance, inflammation, and lipid oxidation and metabolism."

The current study aimed to identify potential metabolites that differed depending on egg intake and whether these were associated with new-onset type 2 diabetes in this cohort using liquid chromatography quadruple time-of-flight mass spectrometry to analyze serum samples.

The study involved 2682 men in the Kuopio area who were 42, 48, 54, or 60 years old in 1984 to 1989. At baseline, the men filled out a 4-day food record, guided by a list of 126 common foods and beverages in Finland at the time.

The researchers then determined the egg intake for each participant, taking into consideration the egg content of certain dishes.

After a mean follow-up of 19.3 years, 432 men developed type 2 diabetes.

The researchers randomly selected 264 participants who had a BMI of 20 to 30 kg/m2 and a daily calorie intake of ≥ 1700 calories/day and divided them into four equal groups for metabolomics analysis.

After excluding men with missing samples, this left 239 men for the analysis:

  • controls with high egg intake (mean 1 egg/day; 61 men);

  • controls with low egg intake (mean 2 eggs/week; 60 men);

  • new-onset diabetes with high egg intake (60 men);

  • new-onset diabetes with low egg intake (58 men).

Men with higher serum levels of tyrosine were around twice as likely to develop type 2 diabetes during follow-up (odds ratio [OR], 1.94; P < .001), as were men with an unknown hexose-containing compound (OR, 2.13; P < .001), regardless of egg intake.

Tyrosine and this unknown compound were positively correlated with several metabolites such as monoglyceride (16:1) that were higher in the participants who ate fewer eggs.

And these two compounds were negatively correlated with other metabolites, such as lysoPC (16:0) that were higher in those who ate more eggs.

However, "other than those two correlations," Noerman and Virtanen noted, "the metabolites that had significant correlation with both tyrosine and the unknown hexose-containing compound remain to be identified."

Dietary Cholesterol in Eggs Unlikely Explanation

Few population studies have enough individuals with high egg intake (> 1 egg/day) to be able to investigate the associations with disease risk with even higher egg intakes than this, the researchers concede.

Therefore, to have information on the health effects of higher intakes (and to have information on causality), clinical trials such as the Diabetes and Egg (DIABEGG) study are needed. In this Australian study, published last year, men who ate more eggs had a higher total intake of cholesterol than their counterparts who ate fewer eggs, but this different intake level was not reflected in their blood cholesterol profiles.

"For most people, dietary cholesterol has only a small impact on blood cholesterol concentrations, so this was not a very unexpected finding," Noerman and Virtanen noted.

"We have also reported this lack of an association [of intake of eggs] with blood lipids before in a larger sample of men from the KIHD study."

Thus, "dietary cholesterol from eggs or endogenous cholesterol most likely does not explain the lower diabetes risk with higher egg intake.”

“Some other compounds in eggs (for example, choline and other bioactive compounds) may have a role, but further investigations are required to explain this relationship."

The researchers have reported no relevant financial disclosures. Vega is a consultant for Johnson & Johnson and speaker for Shire Pharmaceuticals.

Mol Nutr Food Res. Published online December 12, 2018. Abstract

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