Just like a car needs different kinds of oils for its various functioning like fuel for running, brake oil for proper brake functioning, engine oil for engine lubrication and functioning, our bodies too needs different kinds of foods for different needs. However like cars, our nutrient sources are not segregated; some of the foods have higher content of one nutritional ingredient than other. Proteins, the body building and muscle building foods are found in certain kinds of foods, which if not taken sufficiently can lead to poor muscular functioning and strength. It is especially essential for growing children and body building aspirants. It is best had directly from food and not via supplements. You can learn about the top food sources of proteins in the article shared below.