Human protein requirements

In 2002, an expert consultation of international amino acid/protein scientists was convened by the United Nations World Health Organization, Food and Agriculture Organization, and University (WHO/FAO/UNU) to evaluate studies to-date and make recommendations for human protein intake (WHO/FAO/UNU Expert Consultation, 2007). That body had previously asked Rand et al. (2003) to prepare a meta-analysis of nitrogen balance studies. The meta-analysis, consisting of 235 individual subjects across 19 studies was used in the 2007 report, along with other research to make these current WHO/FAO/UNU Expert Consultation (2007) recommendations. The amino acid requirements for adults in the previous EAO/WHO/UNU Expert Consultation Report in 1985 (EAO/WHO/UNU Expert Consultation, 1985) had been taken directly from the 1973 EAO/ WHO report (EAO/WHO, 1973). However, since 1985 concern had arisen regarding the previously derived values and that the values for adults were too low (WHO/EAO/UNU Expert Consultation, 2007). 

TABLE 2.2 Comparison of the 1985 FAO/WHO/UNU and 2002 WHO/FAO/UNU Expert Consultations° mean adult indispensable amino acid requirements without the coefficient of variation added 

Amino Acid 2002 (mg/kg body weight/day) 2002 (mg/g protein ) 1985 (mg/kg body weight/day) 1985 (mg/g protein)  

Concerning the major differences in recommendations, the increases of 150% in mg/kg body weight/day adult requirement for lysine and 114% increase in requirement for threonine between the two report recommendations are of particular significance. Cereal proteins are particularly deficient in these amino acids (Young et ah, 1998) and as shown earlier, cereals are the major dietary staple across Africa. 

TABLE 2.3 Amino acid scoring patterns mg/g protein requirements of infants, children, adolescents and adults over 18 (genders combined)° 

Comparison of the actual amino acid composition of rice and lentils with the ideal pattern illustrates the fact that all staple cereals are deficient in lysine while legumes have an inadequate amount of methionine. 

Mixed diets with plenty of animal foods will get fairly high-qnality scores vegetarian diets including rice, beans, and corn may score almost as high but those based on wheat, sorghum, and cassava will, mostly because of relatively low amounts of lysine in those staples, score only around 70, or even as low as 60. In order to ensure adequate amounts of all the essential amino acids, infants given such a low-quality diet would have to consume 40-70% more of the actual dietary protein than if they wonld have access to dairy products, meat, and fish.  

---

Garza, C., Scrimshaw, N. S., and Young, V R (1977). Human protein requirements A long term metabolic nitrogen balance study in young men to evaluate the 1973 FAO/WHO safe level of egg protein intake. /. Nutr. 107,335-352. 

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. 

This chapter sets out the role and importance of protein in human health, human protein requirements, and the measurement of food protein quality. Specifically, focus is given to the need to improve sorghum protein quality and the developments that have already taken place in this area are reviewed. Lastly, the improvements in sorghum protein quality achieved to date in the Biosorghum project are presented and on the basis of these data, the potential of biofortified sorghum to improve children s nutritional status is evaluated. 

Garza C, Scrimshaw NS, Young VR. Human protein requirements the effect of variations in energy intake within the maintenance range. Am J Chn Nutr. 1976 29(3) 280-7. 

Microbial organisms in several instances are not suitable for the production of large therapeutic proteins. Most human proteins require, for activity, glycosylation and other posttranslational modifications (PTM) that bacteria are unable to perform correctly. Mammalian cell lines are the best expression systems for these products. Most recombinant proteins belong to the WHO... 

In order to approximate the total people affected by malnntrition, it is necessary to look first at human protein requirements and at access to food. Contrasting the... 

FAO/WHO/UNU. 1985. Energy and Protein Requirements. Geneva WHO Pellett, P. L. 1990. Protein requirements in humans. American Journal of Clinical Nutrition 51 723-737. Human protein requirements will be detailed in chapter 8. 

The primary cellular function of mRNA is to direct biosynthesis of the thousands of diverse peptides and proteins required by an organism—perhaps 100,000 in a human. The mechanics of protein biosynthesis take place on ribosomes, small granular particles in the cytoplasm of a cell that consist of about 60% ribosomal RNA and 40% protein. 

Twenty different amino acids ate required fot protein synthesis, of which nine ate essential in the human diet. The quantity of protein required is affected by protein quahty, enetgy intake, and physical activity. 

In an early application of in silico approaches to predict human VD, Ritschel and coworkers described an approach using artificial neural networks (ANN), in this case for VDp [34]. However, this was not a truly in silico-only approach as the ANN that yielded accurate predictions of human VD required animal pharmacokinetic data as input parameters, along with in vitro data (protein binding and logP). 

Figure 26.1 Immortalization of human cells Cells enter replicative senescence at mortality stage 1 (Ml Hayflick limit) after about 60 population doublings (PD). The protein p 16 accumulates in senescent cells. The simian virus 40 (SV40) large T antigen as well as the human papilloma virus (HPV) type 16-E6 and E7 proteins sequester the retinoblastoma protein (Rb) and/or p53 constitutively releases the transcription factor E2F. E2F induces expression proteins required for progression through Gl/S transition, thus the cells escape cell cycle arrest. At mortality stage 2 (M2), transformed cells must overcome senescence and crisis before they are immortalized. This is likely to involve the activation of telomerase either by the introduction of hTERT cDNA or by a genetic change that activates telomerase.

The proliferation of cytotoxic T-cells is markedly impaired upon infection with a newly discovered human immunodeficiency virus, designated HIV-V. The defect has been traced to the expression of a viral-encoded enzyme that inactivates a host-ceU nuclear protein required for DNA replication. Which protein is a potential substrate for the viral enzyme ... 

Blake N, Lee S, Redchenko I, Thomas W, Steven N, Leese A, Steigerwald-Mullen P, Kurilla MG, Frappier L, and Rickinson A (1997) Human CD8+ T cell responses to EBV EBNAl HLA class I presentation of the Gly-Ala-containing protein requires exogenous processing. Immunity 7 791-802. 

The second syndrome, characterized by rhinitis, asthma, or both, is an immediate-type airway response mediated by IgE antibodies directed against trimellityl-human protein conjugates. A latent period, ranging from weeks to years, is required between the sensitizing exposure and the onset of symptoms, but once sensitization has occurred, symptoms occur almost immediately on reexposure. 

Schubert U, Anton LC, Badk I, Cox JH, Bour S, Bennink JR, Orlowski M, Strebel K, Yewdell JW (1998) CD4 glycoprotein degradation induced by human immunodeficiency virus type 1 Vpu protein requires the function of proteasomes and the ubiquitin-conjugating pathway. J Virol 72 2280-2288... 

---