- Proteins are composed of amino acids and are essential building blocks and enzymes in the body. The body requires amino acids from diet as it cannot produce or store them. - Nutrition involves selecting, preparing, and consuming foods that provide nutrients. A balanced diet contains all necessary nutrients in appropriate amounts. - Key components of a balanced human diet include proteins, fats, carbohydrates, vitamins, minerals, fiber and water. Each nutrient has an important role and deficiencies can cause health issues.