Essential amino acids are the building blocks for proteins. For mammalian organisms, amino acids are the only dietary source of nitrogen for protein synthesis. Malnutrition due to protein-calorie insufficiency is one of the major nutritional problems worldwide. In young children, protein-calorie malnutrition is the worlds most important and devastating nutrition problem causing diseases such as kwashiorkor, which is caused by a deficiency of protein or certain amino acids, and marasmus, which is essentially a lack of calories which affects protein utilization and function. Protein intakes vary widely in various parts of the world. The wide range in total protein intakes is probably because of differing consumptions of meat protein, which is linked to the economy of different regions in the world. In addition, individuals suffering from a lack of protein or those who may have variations in intakes of dietary protein either because of choice or due to physiological impairment or disease, deficiencies may be seen in chronic alcoholics with abnormal diets, those who abuse drugs, those with various behavior abnormalities, or those dealing with food fads.
Protein deficiencies affect many aspects of metabolism. Foreign substances, together with endogenous compounds, e.g., steroid hormones, all may be metabolized in vivo. Subsequently, hormonal balance, pharmacological activity of substances, acute toxicity, and carcinogenesis all may affect the metabolism of toxicants. Lack of protein affects enzymes, including enzymes responsible for toxicant metabolisms. The reactions that these enzymes catalyze are affected, because of the amino acids quality or quantity required for protein synthesis that goes into the production of metabolizing enzymes. Lack of protein may lead to changes in amino acid composition of enzymes, which, in turn, may affect substrate binding or interaction with the enzyme.
Examples of enzymes; Cytochrome P450-dependent mixed-function oxidase, primarily located in the liver, is generally considered to be the predominant enzyme involved in detoxification. Also important are various conjugation enzymes, which help form products that are more water soluble and excretable.
Protein intakes are variable in different parts of the world. Industrial nations consume twice the recommended levels. The answer to the question of whether such consumption is detrimental to health is still being debated. Some stress concern that high-protein diets may increase renal stress and subsequently impair function. Bone demineralization, increased colon cancer because of changes in lower gut bacteria, and obesity are other concerns that may be related to high-protein diets. Also, there is the fear that amino acid supplements may result in amino acid imbalances.
High-protein diets enhance oxidative drug metabolism in humans. High protein diets may result in lower toxicity of chemicals.