The nutritional value of plant-based diets in relation to human amino acidand protein requirements

The adequacy of plant-based diets in developed and developing countries as sources of protein and amino acids for human subjects of all ages is examin ed. Protein quantity is shown not to be an issue. Digestibility is identifi ed as a problem for some cereals (millet (Panicum miliaceum) and sorghum (S orghum sp.)) and generally is poorly understood. Direct measurements of bio logical value in children are reviewed and scoring is considered. Various e xisting requirement values for amino acids and especially lysine are review ed, and it is concluded that stable-isotope studies do not yet provide adeq uate alternative values to N balance data, which for lysine are robust afte r recalculation and adjustment. A new maintenance requirement pattern is de veloped, with higher values than those of Food and Agriculture Organization /World Health Organization/United Nations University (1985) but lower value s than the Massachusetts Institute of Technology pattern (Young et al. 1989 ). Calculations of age-related amino acid requirements are based on most re cent estimates of human growth and maintenance protein requirements, a tiss ue amino acid pattern and the new maintenance amino acid pattern. These val ues appear valid when used to score plant proteins, since they indicate val ues similar to or less than the biological value measured directly in young children. When used to score plant-based diets in India, no marked deficie ncies are identified. All regions score >1 for adults, whilst for children scores range from >1, (Tamil Nadhu) from 6 months of age to 0.78 (West Beng al), rising to 0.9 in the 2-5 year old, consistent with reports that high-l ysine maize supports similar weight and height growth to that of casein. In adequate amino acid supply is not an issue with most cereal-based diets.