Eggs are a very good source of low-cost, high-quality protein. Since eggs are high in cholesterol and public health advocates have long recommended that cholesterol consumption be limited to no more than 300 milligrams per day, people with high cholesterol levels have been recommended to avoid eggs. However, several recent studies suggest that instead of contributing to heart disease, eggs actually lower the risk. These results highlight the exceptional nutritional profile of eggs and the fact that saturated fat in the diet, not dietary cholesterol, is what influences blood cholesterol levels most.
A statistical analysis of 224 dietary studies carried out over the past twenty-five years that had investigated the relationship between diet and blood cholesterol levels in over 8,000 subjects clearly demonstrated that saturated fat is more significant in raising blood cholesterol levels than dietary cholesterol.
In addition, in a study published in the the journal of the american medical association, it was shown that people who reported eating four eggs per week had a significantly lower mean serum cholesterol concentration than those who reported eating one egg per week (193 milligrams per deciliter versus 197 milligrams per deciliter). The bottom line from all of the existing research is that most people can eat 1 to 2 eggs a day without measurable changes in their blood cholesterol levels.
Eggs are rich in several nutrients that promote heart health. For example, they are a rich source of betaine. Researchers found that betaine can reduce levels of homocysteine, a metabolite of the amino acids methionine and cysteine. Homocysteine can damage the blood vessel walls. Not surprisingly, elevated homocysteine levels are linked to increased risk for heart disease as well as other chronic diseases, including neural tube defects, osteoporosis.
Like folic acid, betaine plays a role in converting homocysteine to nondamaging forms. Folic acis is the primary agent in the conversion of homocysteine in all cells, while betaine's methylation activity is confined mainly to the liver.
Eggs are also a rich source of choline, a key component of many fat-containing structures in cell membranes, providing flexibility and structural integrity. Two fat-like molecules in the brain, phosphatidylcholine and shingomyelin, account for an unusually high percentage of the brain's total mass, so choline is particularly important for brain function and health.
One large egg provides 300 micrograms of free choline (allin the yolk) and also contains 315 milligrams of phosphatidylcholine.
During pregancy and breast-feeding, an adequate supply of choline is particularly inportant, since choline is essential for normal brain development.
In traditional Chines medicine, eggs are recommend to strenghten one's blood and energy by enhancing digestive and kidney function.