Egg white vs Yolk - Health impact and Nutrition Comparison

Introduction

Egg whites and egg yolks serve separate, distinct purposes in nature. Because of this they have very different nutritional profiles. In this article, we will dive into their specific differences or similarities, and see how they affect our health.

Egg yolk functions as the main source of nutrients for the chicken embryo. Egg whites, on the other hand, primarily play a protective role for the embryo, being situated between the embryo and the hard eggshell, while also providing additional nutrition. Egg whites are also often called albumen, based on the protein it contains most of.

Taste and Use

Because of the nutritional differences, yolk tastes richer than egg white. Egg white is often used to add airy texture and foam to a dish, while yolk can act as an emulsifier.

Egg white is often separated from the yolk to make meringue, macaroon or just egg white omelettes.

Egg yolk can also be used on its own to make mayonnaise, custard and hollandaise sauce.

Interestingly, egg whites have been used not only in the kitchen, but also as a binding agent in photography, in bookbinding and wine making, while yolk has been used in painting and microbiology.

Sizes

Naturally, different sizes of eggs contain different amounts of the same nutrients. The USDA has divided egg sizes into five groups (1).

• Small: 43g (1.5oz)
• Medium: 50g (1.75oz)
• Large: 57g (2oz)
• Extra-large: 64g (2.25oz)
• Jumbo: 71g (2.5oz)

Of this, egg white accounts for about 67% of the liquid weight, whereas yolk makes up the 33% (2).

Nutrition

We know that yolk and egg white are both highly nutritious, but which one provides more macronutrients, minerals and vitamins?

Macronutrients and Calories

Egg yolk is a lot more dense in nutrients, containing only 52% water, whereas egg white consists 88% of water.

One average size of egg white is considered to be 33g, while yolk’s serving size is equal to 17g.

Calories

Egg yolk alone is a very high calorie food, containing 322 calories per 100g. However, yolk is usually not consumed in those amounts. One serving size of yolk contains 55 calories.

Egg white has much less calories with 52 calories in a hundred grams.

Protein and Fats

Yolk is much higher in both protein and fats compared to egg white.

The protein found in yolk and egg white is highly nutritious, containing large amounts of all essential amino acids. Yolk protein is a little richer in most of those amino acids.

The predominant fat type in yolk is monounsaturated fat, closely followed by saturated fat, leaving polyunsaturated fatty acids in last place. 

Egg yolk also contains large amounts of cholesterol. We will discuss the effects of this substance on our cardiovascular health in the “Health Impact” section.

One of the most important fats found in yolk is called lecithin. This fat is partially responsible for many health effects and physicochemical properties of egg yolk, including the yellow colour.

Egg white contains only a negligible amount of fats.

Carbohydrates

Yolk also contains higher amounts of carbohydrates. However, both egg white and yolk do not contain fiber and are very low in sugars.

Vitamins

Yolk is much richer in all vitamins except for one. Egg white contains more vitamin B3.

Four vitamins can be found in yolk that are completely absent in egg whites. Those are vitamin A, vitamin E, vitamin D and vitamin K. The reason for this difference is the fact that these vitamins are all fat-soluble and cannot exist in the fat-free environment of egg whites.

Other vitamins that yolk is higher in include vitamins B1, B2, B5, B6, B12 and the folate form of vitamin B9.

Both egg white and yolk completely lack vitamin C.

Minerals

Egg yolk is higher in almost all minerals as well. Yolk contains higher amounts of iron, phosphorus, calcium, selenium, zinc, copper, manganese and choline. Yolk is also much lower in sodium.

Egg white, on the other hand, is richer in magnesium and potassium.

Glycemic Index

Both egg white and yolk contain so little carbohydrates that measuring the glycemic index would be exceedingly difficult.

Eating egg white or yolk alone should not have much effect on your blood glucose levels (3).

Acidity

Egg white is a naturally alkaline food with a pH value that can range from 7.6 to 9.2. The alkaline properties of the egg white increase as the egg ages (4).

Egg yolk, on the other hand, has a pH value ranging from 6 to 6.9, making it acidic. The acidity of egg yolk also increases during the egg storage (4).

The acidity of the whole egg tends to be neutral.

Another way to look at the acidity of foods is the potential renal acid load (PRAL). The PRAL shows us how much base or acid the given food produces in our bodies.

The PRAL value for egg white has been calculated to be 2.1, making it acidic. Egg yolk has a higher acidic PRAL value of 18.1 

Weight Loss

Egg whites are much lower in calories, as well as all macronutrients, compared with yolk. However, one serving of yolk, containing 55 calories, can also provide the body with many essential minerals and vitamins.

Eggs, overall, have been found to enhance weight loss, when they were incorporated in energy-deficit diets (5). So even with the high calorie yolk, they can be a great addition to a weight management diet.

It has been studied that dietary egg white protein reduces body fat mass in rats by accelerating certain liver functions (6).

The blood level of an enzyme called cholecystokinin increases after egg yolk consumption. This may be the reason for the property of whole eggs or egg yolk to induce greater satiety and reduce short-term food intake compared to other foods with the same amount of calories (7). 

Egg white is the right choice between these two for low calorie, low carb and low fat diets.

Health Impact

As we can see egg white and yolk are rich in different macronutrients, minerals and vitamins. In this section we will focus on what that means for our health.

Health Benefits

Cardiovascular Health

Egg white contains an insignificant level of fats, while yolk is high in cholesterol. We’ve all heard how cholesterol can be dangerous for our cardiovascular health. However, a moderate amount of cholesterol, consumed in a healthy diet, is not only harmless, but also necessary for many functions of the organism (8).

Scientists have found that moderate egg or egg yolk consumption is not associated with an increased risk of cardiovascular disease or stroke among healthy individuals (9). But for people with already existing cardiovascular health issues, in need of controlling their cholesterol levels, it is better to opt for egg whites only or reduce whole egg consumption (10).

Diabetes

Even though both egg white and yolk have very low glycemic indices, their consumption is overall not advised for people at risk of diabetes.

High levels of whole egg consumption has been found to have an association with increased risk of diabetes mellitus type 2, as well as heart disease risk for people with diabetes (11, 12).

Possible mechanisms for these effects are the oxidative and inflammatory effects of choline found in yolk and slower carbohydrate absorption from chemicals found in egg whites (13).

In contrast to this, some studies found there to be either inverse or no association between high egg consumption and diabetes (14, 15).

Downsides and Risks

Cancer

Quite a few studies have suggested a correlation between egg consumption and certain types of cancers.

One research in particular, found high egg consumption to increase the risk of several cancers: oral cavity and pharynx, upper respiratory and digestive tracts, colorectal, lung, breast, prostate and bladder (16).

Another study found that the agents causing lymphosarcomas and lung adenocarcinomas were present in both egg white and yolk, whereas mammary carcinogens were only found in egg yolk (17).

Allergy

Egg allergies are one of the most common allergies in the world, especially in children. Some people may also have intolerance towards egg whites. People are more often allergic to egg whites than yolk, as most allergenic egg proteins are found in egg white (18).

Egg allergy symptoms can range from mild rash, indigestion and coughing to an anaphylactic reaction (19).

Biotin deficiency

Consuming raw egg white for a prolonged period of time can cause biotin deficiency. A protein present in egg white, avidin, tightly binds biotin, also known as vitamin B7, making it unavailable for intestinal absorption. This problem does not occur with cooked eggs as high heat changes the structure of avidin (20).

Salmonella poisoning

Even though 1 in every 20000 eggs may be contaminated with Salmonella bacterium, eating raw eggs may still be hazardous for health (21). Fully cooking eggs kills the bacteria.

Salmonella poisoning symptoms may include nausea, vomiting, diarrhea, fever and stomach cramps. This is particularly dangerous for children, pregnant women and elderly people.

Summary

In summary, egg yolk is much higher in calories and most nutrients, including protein, fats, carbohydrates, vitamin A, vitamin D, vitamins E and K, vitamins B9 and B12, as well as iron, phosphorus and calcium and more. Egg whites are very high in protein, also being richer in vitamin B3, potassium and magnesium.

Moderate consumption of eggs can provide substantial nutrients necessary for overall health, however, excessive intake may lead to detrimental effects, such as diabetes and cancer.

The choice between egg white vs yolk entirely depends on the preferences and needs of the consumer.

Sources.

1. https://www.ams.usda.gov/sites/default/files/media/Shell_Egg_Standard%5B1%5D.pdf
2. https://afs.ca.uky.edu/files/1-composition_of_the_egg.pdf
3. https://www.glycemicindex.com/faqsList.php#8
4. https://www.incredibleegg.org/professionals/manufacturers/real-egg-functionality/ph-stability
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2755181/
6. https://pubmed.ncbi.nlm.nih.gov/28980893/
7. https://www.aeb.org/images/website/documents/food-manufacturers/order-aeb-resources/Short_Term_Effect_of_Eggs_on_Satiety.pdf
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6682969/
9. https://jamanetwork.com/journals/jama/fullarticle/189529
10. https://www.hsph.harvard.edu/nutritionsource/food-features/eggs/
11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2628696/
12. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3683816/
13. https://www.pcrm.org/news/health-nutrition/egg-consumption-increases-risk-diabetes
14. https://pubmed.ncbi.nlm.nih.gov/25832339/
15. https://pubmed.ncbi.nlm.nih.gov/26404366/
16. https://pubmed.ncbi.nlm.nih.gov/20104980/
17. https://journals.sagepub.com/doi/abs/10.3181/00379727-112-28254
18. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3069662/
19. https://acaai.org/allergies/types-allergies/food-allergy/types-food-allergy/egg-allergy
20. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/biotin-deficiency
21. https://extension.umn.edu/preserving-and-preparing/handling-eggs-prevent-salmonella