In spite of the almost universal advice to limit egg consumption because of their high cholesterol content, we think it is good to eat eggs, because the egg is a nearly perfect amino acid food. Furthermore, the egg, because of its high lecithin content and other nutrients, does not raise blood cholesterol levels by more than 2 percent. To consider cholesterol content only is misleading, because the ratio of cholesterol to other nutrients is what is important. This is the reason why Dr. John Yudkin was able to show that sugar and junk foods raised blood cholesterol levels, despite their low cholesterol content.
Most foods are of lower quality as protein sources than the egg, Which is proportionally the most balanced and best source of the essential amino acids. In each food, only one or two essential amino acids are deficient or totally lacking, and these are called the “limiting amino acids” for that food. The protein will be utilized by the body only to the extent that the limiting amino acid is present. The egg’s superior balance makes its proteins more utilizable than those of most other foods.
Careful study of the effect of egg proteins on plasma amino acids shows that egg, like steak, raises lysine, valine, threonine and leucine to extremely high levels. Yet the ratio to other amino acids is slightly better balanced with the egg than with steak. For example, steak increases the plasma valine-to-plasma methionine ratio to more than five to one, while for egg it is only four to one. The egg is slightly better balanced, but not perfectly balanced. Amino acid formulas are now being studied, which may suggest ways to achieve a more balanced rise in plasma amino acids than food itself can provide. At present, the egg is probably the best amino acid food source.