There's a widespread nutritional belief that egg whites are the good part of the egg and that the yolk is bad — the egg white has benefits like protein, whereas the yolk has fat and cholesterol. But maybe it's not as simple as all of that.
Yes, egg whites are a great source of protein with little fat or calories. But despite common misconceptions, they alone might not be as healthy as the whole egg.
The new message that many doctors and dietitians are sending is that the egg yolk might not be as bad as once believed and that it may even have a few health benefits that the whites lack.
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A Brief History on Cholesterol
Eggs were once thought of as one of the primary causes of high cholesterol, a type of fat your body uses to build healthy cells. While cholesterol is useful in the body, the problem is that, with the wrong diet, you can end up with too much cholesterol in your blood. This builds up fatty deposits in your blood vessels, making it difficult for your blood to flow and potentially leading to a heart attack or stroke.
But the Mayo Clinic explains that even though chicken eggs are high in cholesterol, the cholesterol you consume in your diet doesn't necessarily affect the cholesterol in your blood — at least, not as much as people once thought it did. Blood cholesterol is more likely due to excess amounts of trans fat and saturated fat in the diet.
It's for this reason that guidelines for egg consumption have changed over the years. Throughout the '80s and '90s, and even as recently as 2000, people were told to use eggs and egg yolks in moderation, with the emphasis being put on egg whites. It wasn't until 2010 that people were told one egg yolk per day would not raise blood cholesterol levels, and in 2015, recommendations about egg yolks were dropped completely.
The bigger problem egg eaters might face is not necessarily the eggs themselves but the other foods that are served with eggs in the traditional American breakfast, like sodium-heavy meats and trans-fatty oils used for frying, both of which contribute to heart disease risk.
Read more: Should I Be Eating Egg Yolks Every Day?
Comparing the Whites and Yolk
If you compare the nutrients of whole eggs and egg whites only, you'll find whole egg calories are 72 versus egg white calories that are only 17. The whole egg has 186 milligrams of cholesterol while the egg white has none; the whole egg has some fat, including saturated fat, which the whites have only in marginal amounts.
From these numbers, it would seem that egg white benefits outweigh the benefits of the whole egg, with the exception of the protein amount — but to get more protein, you could simply eat more whites. Egg white calories are so much fewer than whole egg calories that if you ate two egg whites, you'd have more protein and half the calories of one whole egg.
Egg white benefits extend beyond these simple numbers too. The American Egg Board notes that the egg white has a lot of nutrients: They have half of the egg's protein, plus most of its niacin, riboflavin, choline, magnesium, potassium, sodium and sulfur. Egg whites have also been shown to aid in satiety, thus helping weight loss efforts. And to make it easier (and less wasteful), you can buy egg whites separately from the yolk in cartons.
According to an October 2012 study published in Nutrients, adding egg white protein to your diet could play a role in protein metabolism. The study looked at the effects of consuming egg white protein or carbohydrates prior to exercise on 30 female athletes over 8 weeks. Egg white protein was not superior to carbohydrates in regards to fat-free mass or one-repetition maximum muscle strength. However, it did contribute to changes in protein metabolism that helps boost overall daily protein intake.
But this isn't the whole picture. Whole eggs, compared with egg whites, are also a rich source of vitamin A and vitamin D. The American Heart Association notes that yolks are good for the eyes because they have amino acids that reduce the risk of cataracts and macular degeneration.
Furthermore, whole egg protein might be better than egg white protein. In a December 2017 study published in the American Journal of Clinical Nutrition, test subjects consumed 18 grams of protein, with one group getting all the protein from egg whites and another group getting it from whole eggs, after engaging in resistance exercise. The study found that protein synthesis was 40 percent greater in those who ate whole eggs.
It's not clear what about whole eggs is better for muscle building and repair, as the same amount of amino acids were available in the blood. The total energy content was different because whole eggs have 17 grams of fat per 18 grams of protein (egg whites have no fat), but the study noted that previous trials showed adding fat to a protein source in a diet doesn't benefit protein synthesis.
Rethinking Eggs and Nutrition
Even though egg white calories and fat are minimal, many people are now willing to consume the extra calories and fat that come with whole eggs because of the added nutritive benefits — and most sources agree that the yolks are not as bad as people once believed.
The American Heart Association emphasizes that people who have heart disease, who have diabetes or who have had a heart attack should still pay close attention to the cholesterol in their diet. If they are not consuming cholesterol from other sources, such as red meat, eggs could be an acceptable inclusion.
Harvard Medical School points out that although eggs (yolks and all) are better than sugary, refined breakfast cereals, muffins and pancakes, they are still not as healthful as a bowl of steel-cut oats with nuts and berries because whole grains and fruit can lower the risk of heart disease. Furthermore, plant sources of protein are linked to lower cardiovascular disease and overall mortality.
Egg whites were once hailed as a healthier alternative to whole eggs, but as more and more people start to understand the nutrients the yolk has to offer, all of that can be expected to change. Still, as many sources point out, it's never a bad thing to practice moderation.
- American Egg Board: “Refrigerated Liquid/Frozen Egg White”
- National Institute of Food and Agriculture: “Whole Eggs Better for Muscle Building and Repair than Egg Whites, Researchers Find”
- American Journal of Clinical Nutrition: “Consumption of Whole Eggs Promotes Greater Stimulation of Postexercise Muscle Protein Synthesis Than Consumption of Isonitrogenous Amounts of Egg Whites in Young Men”
- Nutrients: “Effects of Egg White Protein Supplementation on Muscle Strength and Serum Free Amino Acid Concentrations”
- Mayo Clinic: “Eggs: Are They Good or Bad for My Cholesterol?”
- American Heart Association: “Are Eggs Good for You or Not?”
- Harvard School of Public Health: “Eggs”
- Harvard Medical School: “Eggs and Your Health”
- Mayo Clinic: "High Cholesterol"