Years ago, medical professionals noticed that peculiar disease states were directly related to food intake. These diseases were found in the presence of adequate calorie and protein intake.
Scientists also noticed that these diseases were absent among people who consumed certain foods. For example, sailors who consumed citrus fruits on long sea voyages did not develop scurvy.
Thus, researchers reasoned, there must be other important substances in the foods. Eventually, they discovered that compounds only obtained from foods could prevent and cure these diseases. Keep Reeding