A single large egg packs 6.3 grams of complete protein and over a dozen essential vitamins and minerals into just 78 calories. Few foods deliver this much nutritional variety in such a small, affordable package. Eggs are especially rich in protein, choline, vitamin B12, selenium, iodine, and several fat-soluble vitamins that many people don’t get enough of.
Complete Protein With a Perfect Score
Egg protein has an amino acid score of 100, the highest possible rating, meaning it contains all nine essential amino acids in the proportions your body needs. It also has the highest net protein utilization rate of any whole food, which means your body wastes very little of what it absorbs. A single large hard-boiled egg delivers 6.3 grams of protein split roughly between the white and the yolk.
Cooking matters more than you might expect. Your body absorbs about 91% of the protein in a cooked egg, compared to only 51% from a raw egg. Heat unfolds the tightly wound protein structures, making them far easier to digest. So blending raw eggs into a smoothie gives you roughly half the usable protein of a scrambled or boiled egg.
Choline: A Nutrient Most People Lack
One large egg contains 147 milligrams of choline, about 27% of the daily value for adults. Choline supports brain function, liver health, and cell membrane integrity, yet most people fall short of the recommended 550 milligrams per day. Eggs are one of the richest food sources available. Two eggs at breakfast get you more than halfway to your daily target, something that’s hard to achieve from most other common foods.
Vitamin B12 and Selenium
A single egg provides roughly 1.2 micrograms of vitamin B12, which is significant considering adults need about 2.4 micrograms daily. B12 is essential for nerve function and red blood cell production, and it’s found almost exclusively in animal foods. For people who eat limited meat or fish, eggs are a practical way to maintain adequate levels.
Eggs also supply about 16 micrograms of selenium per egg, a mineral that supports thyroid function and acts as an antioxidant in your cells. Two eggs cover a meaningful portion of an adult’s daily selenium needs, which range from 55 to 70 micrograms depending on the country’s guidelines.
Iodine for Thyroid Function
One large hard-boiled egg contains 31 micrograms of iodine, about 21% of the daily value. Iodine is a building block for thyroid hormones, which regulate your metabolism, energy levels, and body temperature. Without enough iodine, the thyroid enlarges as it tries to compensate. While iodized salt is the most common source for many people, eggs contribute a steady baseline, especially if you’ve been cutting back on salt.
Eye-Protecting Antioxidants
Egg yolks get their deep yellow color from lutein and zeaxanthin, two antioxidants that accumulate in the macula of your eye, the region responsible for sharp central vision. These compounds help filter damaging blue light and protect against age-related macular degeneration. What makes eggs stand out isn’t the total amount of these antioxidants (spinach and kale contain more per serving) but their bioavailability. The fat in the yolk helps your body absorb them efficiently. One study found that adding egg yolk to the diet increased blood levels of lutein by 28 to 50% and zeaxanthin by 114 to 142%, depending on the background diet.
Healthy Fats and Omega-3 Variations
A large egg contains 5.3 grams of total fat, with only 1.6 grams of saturated fat. The rest comes from heart-friendlier monounsaturated and polyunsaturated fats. However, not all eggs are equal when it comes to omega-3 fatty acids. Pasture-raised hens that forage on grass and insects produce eggs with roughly three times more omega-3s than conventional cage-free eggs. One comparison found that the ratio of omega-6 to omega-3 fats was 51:1 in cage-free eggs but dropped to between 6:1 and 11:1 in pasture-raised eggs. A lower ratio is generally associated with less inflammation.
If boosting omega-3 intake is a priority for you, pasture-raised or omega-3 enriched eggs offer a real advantage over standard grocery store eggs.
Vitamin D in the Yolk
Egg yolks are one of the few natural food sources of vitamin D, which is critical for calcium absorption and bone health. A standard egg provides a modest amount, typically around 1 to 1.5 micrograms (40 to 60 IU). That’s a small fraction of the 600 IU most adults need daily, so eggs won’t solve a vitamin D deficiency on their own. But they contribute to your total intake alongside sunlight exposure and other dietary sources. Eggs from hens fed vitamin D-enriched diets can contain significantly higher levels, sometimes several times the standard amount.
What About Cholesterol?
A single large egg contains about 186 milligrams of dietary cholesterol, all of it in the yolk. For decades, this made eggs a nutritional villain. That picture has shifted considerably. The American Heart Association supports daily consumption of one whole egg for healthy individuals with normal cholesterol levels. The U.S. Dietary Guidelines removed the longstanding cap of 300 milligrams of dietary cholesterol per day, recognizing that for most people, dietary cholesterol has a smaller effect on blood cholesterol than once believed.
Research on large populations generally supports one egg per day as safe for the general public. The evidence gets less clear at two or more eggs daily, and people with high cholesterol or existing heart disease should be more cautious with very high intake levels. For the average healthy person, though, the nutrient benefits of a daily egg comfortably outweigh the cholesterol concern.
Nutrient Summary at a Glance
- Protein: 6.3 g (complete, with all essential amino acids)
- Choline: 147 mg (27% daily value)
- Vitamin B12: 1.2 mcg (roughly half the adult daily need)
- Selenium: 16 mcg (about 23% of the adult recommendation)
- Iodine: 31 mcg (21% daily value)
- Total fat: 5.3 g (mostly unsaturated)
- Calories: 78
Eggs also supply smaller but meaningful amounts of vitamin A, folate, phosphorus, and riboflavin. The yolk carries the vast majority of these micronutrients, so eating only egg whites means losing most of the nutritional value beyond protein.