An Egg a Day May Be Too Much

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Egg consumption and risk of type 2 diabetes in men and women, by Luc Djoussé and colleagues. Diabetes Care 32:295–300, 2009

What is the problem and what is known about it so far?

Eggs are high in cholesterol, but also contain minerals, vitamins, protein, fats, and other nutrients. While cholesterol and saturated fat may raise the risk for getting diabetes, some of the other nutrients in eggs may lower that risk. Some studies have suggested that eating eggs frequently may have bad health effects (such as raising the risk of heart or blood vessel disease) for people who already have type 2 diabetes. However, it is not known whether eating eggs raises the risk of getting diabetes for people who don't already have it.

Why did the researchers do this particular study?

The researchers wanted to find out whether eating eggs frequently raises a person's risk of getting type 2 diabetes.

Who was studied?

The study used data from more than 20,000 men and more than 36,000 women who had participated in two previous large medical studies.

How was the study done?

Researchers learned from the previous study's questionnaires and results about how many eggs participants ate per week and how many participants developed diabetes over the next 20 years for men or 11 years for women. They looked at the results to see if there was a link between the number of eggs eaten and later development of diabetes.

What did the researchers find?

The more eggs a person ate per week, the higher the chance that he or she would get diabetes. Eating eggs once a week or less often did not raise the risk of diabetes. But compared to people who don't eat eggs, men who eat more than seven eggs each week were 58 percent more likely to get diabetes, and women who ate more than seven eggs each week were 77 percent more likely to get diabetes. Eating eggs frequently raised the risk even after researchers took diabetes risk factors, high cholesterol (blood fat) levels, and other diet information into account.

What were the limitations of the study?

The researchers were unable to repeatedly test blood glucose and other measures during the follow-up period, so they couldn't learn exactly how eggs may increase the risk for diabetes. The study design, which involved looking at existing data, might have affected the results. Also, participants' reports of how many eggs they ate each week and whether they later got diabetes may not have been accurate. There was no information about whether participants ate whole eggs including yolks, which have more cholesterol, and only limited information about the other foods they ate, which could have affected results. Finally, the participants all had similar characteristics and most were white. Therefore, the findings might not hold true for everyone.

What are the implications of the study?

Although more study is needed, people who currently eat one or more eggs each day may want to eat eggs less frequently to help prevent diabetes.

FOR MORE INFORMATION

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