Eggs. Eggs' protein content makes them a satisfying breakfast option as well as a good supply of nitrogen. The egg yolk, on the other hand, still contains protein. It is also high in other nutrients. Eating one whole egg daily provides about 6 grams of protein. Egg whites have less protein than the yolks, but they are also low in fat and high in vitamin D. One large egg white has only 4 grams of protein while the yolk has 50 grams. People who follow a vegan diet (without any animal products at all) have been known to survive on nothing but plants for several years. However, such a diet is difficult to maintain for more than a few months without some type of protein intake. Beans, peas, nuts, and soy products are all good sources of protein for those who don't eat meat. Nitrogen is found in foods of natural origin such as meats, vegetables, fish, milk, etc. Therefore, eggs meet this requirement for protein. Milk contains varying amounts of protein depending on the product. For example, milk produced from cows fed grain-based diets will usually have less protein than milk produced from cows given grasses as part of their diet. Eggs are a great source of protein, with one large egg having six grams of protein.