Plant-based foods such as vegetables, fruits and grains are low in protein, while animal products such as meats, cheese, milk and eggs are rich in protein. Some foods, such as beans, have larger amounts of protein than most vegetables, but it is not as easily absorbed as protein from animal-based foods.
A diet rich in protein is not harmful to most people and may have benefits. However, people with liver or metabolic disorders must eat smaller amounts of protein. The body requires protein for synthesizing essential amino acids and for other vital biological processes.
For individuals with kidney disorders, excess protein results in unsafe levels of the chemical urea. In healthy people, the kidneys quickly move urea out of the body, but excessive levels of this chemical can cause appetite loss, fatigue and other symptoms. Those with metabolic disorders cannot eat large amounts of protein, as doing so causes the build-up of other undesirable chemicals.
Because protein is an essential nutrient, even for people with damaged kidneys or metabolic disorders, these individuals must carefully incorporate small amounts of protein into their diets. Substituting vegetables for protein or using vegetable-based meat and dairy substitutes gives those on low-protein diets the necessary nutrients while preventing harmful chemicals from accumulating.