The building blocks that make up all proteins are called amino acids. Various combinations of the same twenty two- amino acids, put together as are the letters of the alphabet that can form a whole dictionary of words with different meanings, make all of the proteins in nature. Proteins are found in all foods derived from animals and plants, unless they have been removed or altered by refining processes. Only eight of the twenty-two amino acids are essential to us, because they cannot be made in human metabolism. These eight essential amino acids must be present in sufficient quantities in our food for us to enjoy good health.
Water makes up a large part of our foods.
Although it yields no energy, for many reasons water is an essential element for life. Approximately 60 percent of body weight is water. Because the four nutrients discussed above - carbohydrates, fats, proteins, and water make up the largest portion of any foodstuff by weight, they are often referred to as macronutrients. Vitamins are organic compounds that are synthesized for the most part only by plants and bacteria. Thus, our supply of vitamins must come from plant foods and our own bowel bacteria.