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Keep perspective when assessing research studies on links between food and health

As consumers who want to make wise food choices for ourselves and our families, it’s easy to become confused—even frustrated—as we try to make sense of everything we read about the link between our diet and our health.

Mainstream and online media are full of reports on the latest studies examining the health benefits and risks of consuming specific foods and beverages. Beyond dealing with the volume of information, we’re often unsure about the “facts”; frequently, the scientific research we read about today contradicts another study that made headlines last month.

I would offer one general piece of advice—understand that a single study doesn’t constitute “a scientific body of evidence.” Like all science, the science of nutrition evolves over time. Along the way to developing the best evidence of a link between food and health, we will run into unusual and contradictory findings—signalling a need for further investigation.

It’s also helpful to dig deeper when assessing new research and media reports about it. I recognize that it’s difficult to give the full picture in a news item—all the nuances associated with a study, and the cautions that researchers may express about drawing conclusions.

In this vein, I’d like to provide some additional perspective on a column by Leslie Beck called “Good eggs, bad eggs,” published in the Life section of The Globe and Mail on June 13, 2013.

Ms. Beck discusses a study recently published online in the American Journal of Clinical Nutrition. This study was a “meta-analysis”—analysis of the combined results of a number of published studies. The authors said their review suggested that:

Eating one egg a day was not associated with a higher risk of cardiovascular disease in the general population (i.e., in healthy people). This finding is not new or surprising; it is consistent with decades of research showing that daily egg consumption is not linked to development of heart disease in the general population, as well as among people with existing high blood cholesterol.

People with type 2 diabetes who ate one egg per day had a 69 per cent higher risk of cardiovascular disease, than did those with diabetes who ate fewer than one egg per week or none. Previous studies have indicated that people with diabetes do have a greater risk of developing heart disease when eating more eggs, and we know that more research is needed in this area to fully understand why this is the case.

Healthy individuals consuming one egg a day (again, compared to fewer than one a week or none) were 42 per cent more likely to develop type 2 diabetes. This suggestion is indeed surprising, as I have never before seen results indicating that higher egg consumption could increase the risk of developing diabetes.

The authors themselves note the findings don’t allow assessment of other factors contributing to development of diabetes. As we know, diabetes stems from a number of complex factors, such as age, weight, inactivity and heredity—and this analysis could not show other risk factors the “egg eaters” might have had in common. No cause-and- effect relationship can be established.

According to the authors, “The results should be interpreted with caution and may not justify changes in current dietary advice on egg consumption until more scientific data becomes available”.

Additional perspective can be found in the Canadian Diabetes Association’s 2013 Clinical Practice Guidelines, which recommend that people with diabetes follow Canada’s Food Guide—in which two eggs are considered a serving of Meats and Alternatives. In addition, the guidelines suggest that a high-protein, low-saturated fat, calorie-reduced diet that includes two eggs a day can be beneficial for people with diabetes.