You may have heard last week that JAMA released a new study drudging up the age old debate about whether eggs are bad for you. I first became aware of this study when I saw an article about it on the front page of CNN – “Eggs: three or more per week can increase your risk of heart disease”. I was kind of delighted because it gave me a chance to dust off this old post from 2014!
About the egg study
This study is what we call an observational study where participants are given a food recall at the beginning of the study and then they are followed over time to evaluate any health issues that develop. The newest egg study actually just used the following 6 studies to extrapolate data:
- Atherosclerosis Risk in Communities (ARIC study)
- Coronary Artery Risk Development in Young Adults (CARDIA study)
- Framingham Heart Study (FHS)
- Framingham Offspring Study (FOS)
- Jackson Heart Study (JHS)
- Multi-Ethnic Study of Atherosclerosis (MESA)
Something significant about an observational study is that it can only be used to establish a relationship or association. You cannot use an observational to establish a cause-and-effect relationship because there are no control or experimental groups. This is a huge issue with the study and why we cannot say, even if the data was solid, that eggs caused increase CVD events.
Another issue with the study is that when you look at the averages of all of the studies, people were followed for 17.5 years. They filled out 1 food recall in the beginning of the study. Who is to say how eating habits changed over time.
Why are eggs so controversial?
Eggs have been looked at in a negative light because they are high in dietary cholesterol. At one point in time, the recommended daily intake for cholesterol was 200mg… an egg has 185mg. However, studies have shown us that there is a very week association between dietary cholesterol intake and the increase of cholesterol in our bodies (serum cholesterol). This association is so weak that cholesterol was actually removed as a nutrient of concern in the 2015 Dietary Guidelines for Americans.
The egg whites and yolks have different nutrient contents. Let’s take a look:
So you can see above that the yolk contains more healthy fats and nutrients like choline and Vitamin A… but it also contains more saturated fat and cholesterol. The saturated fat is pretty minimal in 1 egg –1.6g- but this could definitely add up if you were making something like an omelet with 5-6 eggs. An egg yolk contains ~180 mg cholesterol. The American Heart Association recommends that we consume < 300 mg cholesterol daily for those without CHD and < 200 mg per day for those with CHD.
There was a time when it was believed that eggs had adverse health effects due to the amount of dietary cholesterol they contained. In the 70s, the American Heart Association actually put a limit on the number of eggs that were recommended in the diet per week. Current research contraindicates this:
This study found that daily egg consumption was non-detrimental to lipid levels in hyperlipidemic adults
This study found that consuming 1 egg per day was “unlikely to have substantial overall impact of the risk of CHD or stroke among healthy men and women”
In terms of cholesterol, it’s important to note that many foods high in cholesterol are also higher in saturated fat (bad fats). Eggs, however, have more monounsaturated and polyunsaturated fat (good fats).
My thoughts on eating egg yolks:
I think that current studies support that daily consumption of 1 egg, including the yolk, is not going to be detrimental to your health. Current studies support that saturated and trans fat consumption will have a greater effect on serum lipid levels.
Having said that, it’s important to note that many studies out there have looked at the consumption of only 1 egg per day. Making a dish with a lot of eggs could quickly turn into something high in calories and fat. For example, if you made an omelet with 6 eggs then that would be 432 calories and 9.6 g saturated fat. If you’re making an omelet, scrambled eggs, or any other dish that uses multiple eggs then I would use 1 whole egg per serving/person and stick with egg whites for the rest.