Protein nutrition amino acid requirement

WHO/FAO/UNU Expert Consultation (2007). Protein and Amino Acid Requirements in Human Nutrition. World Health Organization, Geneva Report of a Joint WHO/FAO/ UNU Expert Consultation. World Health Organization Technical Report No. 935. Winick, M. (1979). Hunger disease. Studies by the Jewish Physicians in the Warsaw Ghetto. John Wiley Sons, New York. 

Rama, P. B., Norton, H. W., and Johnson, C. (1964). The amino acid composition and nutritive value of proteins. V. Amino acid requirements as a pattern for protein evaluation. /. Nutr. 82, 88-92. 

University. Protein and amino acid requirements in human nutrition. Report of a joint FAOAVHO/UNU expert consultation (WHO Technical Report Series 935) 2007. 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

Amino acids promote the production of proteins, enhance tissue repair and wound healing, and reduce the rate of protein breakdown. Amino acids are used in certain disease states, such as severe kidney and liver disease, as well as in TPN solutions. (See the last section of this chapter for a more detailed discussion of TPN.) TPN may be used in patients with conditions such as impairment of gastrointestinal absorption of protein, in patients with an increased requirement for protein, as seen in those with extensive bums or infections, and in patients with no available oral route for nutritional intake ... 

When normal enteral feeding in not possible or is inadequate to meet an individual s nutritional needs, intravenous (IV) nutritional therapy or total parenteral nutrition (TPN) is required. Products used to meet the IV nutritional requirements of the patient include protein substrates (amino acids), energy substrates (dextrose and fat emulsions), fluids, electrolytes, and trace minerals (see the Summary Drug Table Electrolytes). 

Not all proteins are nutritionally equivalent. Mote of some than of others is needed to maintain nittogen balance because different proteins contain different amounts of the various amino acids. The body s requirement is for specific amino acids in the correct proportions to replace the body proteins. The amino acids can be divided into two groups essential and nonessential. There are nine essential or indispensable amino acids, which cannot be synthesized in the body histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. If one of these is lacking or inadequate, then—regardless of the total intake of protein—it will not be possible to maintain nitrogen balance since there will not be enough of that amino acid for protein synthesis. 

Dietary protein provides essential amino acids. The quality of a protein is a measure of its ability to provide the essential amino acids required for tissue maintenance. Proteins from animal sources, in general, have a higher quality protein than that derived from plants. However, proteins from different plant sources may be combined in such a way that the result is equivalent in nutritional value to animal protein. 

A mino acid metabolism in vertebrates contrasts sharply with amino acid metabolism in plants and microorganisms. Most striking is the fact that plants and microorganisms can synthesize all 20 amino acids required for protein synthesis whereas vertebrates can only synthesize about half this number. This inability leads to complex nutritional needs for vertebrates. We discuss these needs in light of the pathways for biosynthesis that still exist. 

Young, V. R., and El-Khoury, A. (1995). Can amino acid requirements for nutritional maintenance in adult humans be approximated from the amino acid composition of body mixed proteins Proc. Natl. Acad. Sci. U.S.A. 92,300-304. 

The problem with using plant sources of protein is that they do not provide the proper balance of the amino acids required for human nutrition [70]. Some of the deficient amino acids may be synthesized by the body. But some, the essential amino acids, must be acquired through the diet for proper human nutrition and growth. Commercial production of amino acids has mainly been for animal feed supplementation. However, cereals supplemented with synthetically produced essential amino acids could improve the nutritional value of plant crops to supply the human protein requirement. In this way a proportion of the crops now grown for animal feed could be diverted to human consumption, and more people could be fed from the same area of arable land than would be possible using animal protein. 

Chlorella contains protein, chlorophyll, dietary fiber, and large amounts of minerals and vitamins. The protein of Chlorella contains all the essential amino acids required for the nutrition of animals and humans. 

The nutritive value of a protein depends on its capacity to provide nitrogen and amino acids in adequate amounts to meet the requirements of an organism. Thus, in theory the most logical approach for evaluating protein quality is to compare amino acid content (taking bioavailability into account) of a food with human amino acid requirements. A number of comparisons have been made using reference patterns such as those derived from egg and milk protein. The first major change in procedure was substitution of a provisional pattern of amino acid requirements for the egg protein standard. 

Since biological value is dependent primarily upon essential amino acid constitution, it would seem logical to assess the nutritive value of a protein by determining its essential amino acid constitution and then comparing this with the known amino acid requirements of a particular class of animal. Application of modern chromatographic techniques coupled with automated procedures allows relatively quick and convenient resolution of mixtures of amino acids. However, the acid hydrolysis used to produce such mixtures from protein destroys practically all the tryptophan and a considerable proportion of the cystine and methionine. Tryptophan has to be released by a separate alkaline hydrolysis, and cystine and methionine have to be oxidised to cysteic acid and methionine sulphone to ensure their quantitative recovery. Losses of amino acids and the production of artefacts, which are greater with foods of high carbohydrate content, are reduced if the hydrolysis is carried out in vacuo. Evaluations of proteins in terms of each individual amino acid would be laborious and inconvenient, and several attempts have been made to state the results of amino acid analyses in a more useful and convenient form. 

REQUIREMENTS. Proteins differ in nutritive value mainly due to their amino acid composition. If one essential amino acid is missing from the diet, a certain protein or proteins will not be formed, and an adult will enter a state of negative nitrogen balance while a child or infant will cease to grow. These two facts provide the basis for experimentally determining amino acid requirements. The estimated essential amino acid requirements shown in Table A-2 may serve as a guide for the selection of dietary protein sources. 

Often, individuals subjected to injuries, surgery, and/or infections have a depress food intake which may complicate the nutritive requirements. Once carbohydrate stores of energy (muscle and liver glycogen) are depleted usually within 24 hours energy must be provided by fat and protein stores. Amino acids from the catabolism—breakdown of skeletal muscle are an important energy source. If prolonged, this results in massive tissue wasting. 

---