Which Are Healthier — Egg Yolks or Egg Whites?

Eggs are naturally divided into two parts — the white and the yolk. Egg yolks are healthier than egg whites because they contain more lipids, vitamins, minerals, and other nutrients.

Eggs are a popular food. Many people eat them for breakfast, lunch, dinner, or snacks, and people trying to build muscle eat several daily for their high-quality protein. Eggs are naturally divided into two parts — the white and the yolk. The yolk got a bad reputation for a time for its cholesterol and fat content. People have been eating egg whites and throwing away the yolks for some years now. But both parts have valuable nutrients, and you should eat the whole to get the full health benefits of eggs.

Egg shells are made of calcium carbonate. Their color is commonly white or brown but may be blue or green. The color of an egg has no relation to its nutritional and health benefits. 

Egg white, also known as albumen, makes up about 60 percent of an egg by weight. It consists of 90% water and 10% protein. An average-sized egg has about 6 grams of protein, of which about 4 grams is in the white. A 100-gram portion of egg white contains:

Energy: 52 calories

Protein: 10.9 grams

Total fats: 170 milligrams

Carbohydrates: 0.73 grams

Dietary fiber: none

Iron: 0.08 milligrams

Calcium: 7 milligrams

Phosphorus: 15 milligrams

Vitamin A: none

Vitamin B1: 0.004 milligrams

Vitamin B2: 0.439 milligrams

Vitamin B12: 0.00009 milligrams

Folate: 0.004 milligrams

Vitamin C: none

Vitamin D: none

Cholesterol: none

Egg white is packed with protein but not much else. It provides only minute amounts of most vitamins and minerals and no lipids. 

Eggs whites are a concentrated source of complete protein (has all the essential amino acids) and is easily digested and used by the body. One egg white provides you with 4 grams of protein and only 17 to 20 calories. 

The protein in eggs is a high-quality protein with all the amino acids your body needs and in proportions that allow for efficient utilization. Consuming such protein is helpful if you're trying to build muscle. Including egg whites in your snacks or meals is also a good idea if you're trying to lose weight, as they contain protein but few calories. Proteins are the most satisfying of the major nutrients and keep you from feeling hungry for longer. Satiety is a critical component of a weight loss diet plan.

Cholesterol is a nutrient of concern. High blood levels of cholesterol and low-density lipoprotein (LDL) are linked to heart disease and hypertension. Eggs contain significant cholesterol, but it is all in the yolk. Consuming only egg whites would seem to save you from the dangers of cholesterol. But cholesterol is at its most dangerous when consumed along with an unhealthy diet with excessive amounts of saturated fats. Recent guidelines do not advise limiting cholesterol intake to a number but recommend a healthy eating pattern with as little cholesterol as possible.

Egg white has bioactive proteins like lysozyme, ovalbumin, ovotransferrin, and avidin. Lysozyme kills bacterial cells and protects against infections. Ovalbumin is about half the protein content of egg white and provides amino acids. The functions of most proteins in egg white are not known yet. Egg allergy is usually caused by sensitivity to these proteins in the egg white.

Omega-3 fatty acids

Omega-3 fatty acids have essential actions in the body. The recommended daily intake is 0.25 grams a day. The major dietary sources of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are oily fish or fish oil. But whole eggs also contain omega-3 fatty acids, though in small amounts.

Omega-3 fatty acids are polyunsaturated fatty acids. They reduce blood cholesterol levels. They're also needed to form phospholipids that are necessary for cell membranes. Among the omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) reduce your risk of heart disease, nervous system disorders, and mental health diseases. They also reduce inflammation and prevent chronic diseases.

Cholesterol

Egg yolk contains significant amounts of cholesterol. A 100-gram portion of eggs (which would be about two average-sized eggs) has 372 milligrams of cholesterol. 

Fats

One egg contains about 4.6 grams of fat (approximately one teaspoonful). Only about a quarter of this is saturated fat. Most fats are monounsaturated and polyunsaturated fats that aren't harmful.

Vitamins

Eggs are a good source of vitamins D, B2, and B12. All the vitamins are in the yolk. The vitamin D content varies widely depending on how the hens are housed (outdoors or indoors) and can be increased by feeding the hens vitamin D or exposing them to ultraviolet light. 

Minerals

Egg yolks contain calcium, iodine, iron, magnesium, phosphorus, potassium, selenium, sodium, and zinc. The amounts of minerals in eggs vary depending on the hen's diet.

Choline

Choline is an essential nutrient needed for the building of cell membranes. It is also needed to make acetylcholine, an important signaling chemical for the nervous system. Choline is vital for early brain development. Eggs are an important source of choline in human nutrition. One large boiled egg provides 147 milligrams of choline, which is 27 percent of the daily value (DV). 

Besides beef liver, eggs are the richest source of choline in human nutrition. Choline deficiency can cause nervous system disorders and fatty liver disease. People with good choline intakes have better memory, cognitive performance, and speed of perception. Choline intake could slow the progression of dementia like Alzheimer's disease. 

Phospholipids

The yolk of one egg contains about 5 grams of fat, 30 percent of which are phospholipids. The most abundant is phosphatidylcholine which has anti-inflammatory effects. People eating whole eggs have a reduction in c-reactive protein and tumor necrosis factor alpha (TNFα), markers of inflammation. Another phospholipid in egg yolk is phosphatidic acid. This compound stimulates muscle protein synthesis and increases muscle mass.

Antioxidants

Oxidative stress is a significant cause of chronic disease. Heart disease and some cancers are associated with oxidative stress. Egg yolks contain selenium, carotenoids, and vitamin E. These antioxidants reduce free radicals, prevent age-related degeneration, and reduce the oxidation of fats. These actions reduce the risk of heart disease.

Egg yolks have no dietary fiber and very little carbohydrate. 

Cholesterol content has been seen as a worrying factor in regard to health. The American Heart Association recommended (in 2000) that cholesterol consumption should be 300 milligrams a day or less. Since egg yolks contain cholesterol, eating egg whites and avoiding the yolk became popular.

Recent guidelines don't use such a number but recommend a balanced, healthy diet with as little cholesterol and saturated fats as possible. Most foods rich in cholesterol like dairy and fatty meats also have large amounts of saturated fats. Eggs (and shellfish) are unusual — they contain cholesterol but low amounts of saturated fats.

Eating an egg a day won't raise your blood cholesterol levels. Limiting the saturated fats in your diet is much more important for keeping your blood cholesterol levels low. People eating an egg daily have no higher risk for stroke or heart disease. 

Eating three whole eggs a day is also safe. It doesn't increase heart disease or the risk of death. But some athletes and physically active people eat more eggs than this. The safety of such high egg consumption is unknown.

The body actually needs cholesterol. It is necessary for making steroid hormones. Cholesterol is a raw material for forming vitamin D in the skin through sun exposure. The liver needs cholesterol to make bile which helps in fat digestion in the intestines. 

Eggs contain about 6 grams of complete protein containing all nine essential amino acids needed by the human body (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine). The proteins in eggs are easily digested and absorbed, and the body can use the amino acids. 

The proteins in eggs are considered high-quality because all the amino acids are in adequate amounts. 

These amino acids are needed to produce enzymes, hormones, hormone receptors, DNA components, muscle proteins, and other components required for growth, maintenance, and metabolism.

Besides protein, eggs provide choline, vitamin B12, phosphorus, and riboflavin (vitamin B2). Eggs also contain iodine and selenium. These minerals are not widespread in human food. The protein content of eggs is divided between the white and the yolk, but the lipids, vitamins, minerals, and other nutrients are all concentrated in the yolk.

Eating eggs is popular when building muscle with resistance exercise. Eating whole eggs yields a greater muscle mass increase than eating only egg whites. This is perhaps because the yolk provides energy, too. Increased energy contributes to positive nitrogen balance and greater muscle protein synthesis.

Eggs should be eaten whole to get all their considerable health benefits. Most of the nutrients are in the yolk, but much of the protein is in the white. Whole eggs are a good source of protein, iodine, and vitamins A, D, B2 (riboflavin), B9 (folate), and B12 (cobalamin).

There's no recommendation about the number of eggs you can have. Eat eggs as part of a healthy, balanced diet, and cook them without adding salt or oil. Boiled or poached eggs are best if you don't add salt. Scrambled eggs without butter and using low-fat milk in place of cream are also safe. Frying your eggs increases their fat content by about 50 percent.

Raw or undercooked eggs (eggs with runny yolks) are a hazard. Eggs infected with bacteria, viruses, or parasites look and smell the same as healthy eggs. Always cook them well, ensuring the insides reach a temperature of 160°F (71°C) to avoid foodborne illnesses such as salmonella infection. 

Store eggs in a cool, dry place or a refrigerator. Avoid using eggs that are past their best-before dates. Don't use eggs with cracked shells — bacteria might have got inside them. Always wash your hands before and after handling eggs.

Eggs are inexpensive, easy to store and cook, and a valuable source of high-quality protein, minerals, vitamins, and other nutrients needed for a healthy diet and life. Both the whites and yolk have beneficial components, and the health benefits of eggs are best obtained by consuming them whole.