Hair, skin, muscle, and organs like the heart and liver and their associated enzymes are all manufactured from amino acids. Digestion breaks down proteins to amino acids, which are absorbed and used for building blocks and even for energy production.
Some amino acids are essential to the diet.
Ten of the common amino acids cannot be synthesized by the body in adequate amounts and are classified as essential dietary ingredients, while the rest of the amino acids are made by cells and are generally made in the adequate amounts. Amino acids requirements increase during periods of growth, with pregnancy and lactation, and even with strength training. People relying on reduced calorie diets or incomplete vegetable protein, those who limit protein intake due to sensitivities, and those with imbalanced digestion or absorption may need extra amino acids.