Vernon Young (deceased) was born in Wales in 1937. After graduating from the University of Reading (England), he moved to the United States where he obtained a Ph.D. in Nutrition from the University of California, Davis, in 1965. He then became Assistant Professor, Associate Professor and then, in 1977, Professor at M.I.T. in Boston. He was President of the American Institute of Nutrition in 1991 / 1992. He was also Director of the Mass Spectrometry Facility at Shriners Burns Institute in Boston.
Vernon Young was best known for his contributions to the study of protein and amino acid metabolism, how it changes through the human life cycle, and in response to nutritional deficiencies and injuries such as burns. A series of investigations with Nevin Scrimshaw and other collaborators on nitrogen losses in individuals of various ages showed that dietary protein was less effective in balancing such losses than had been previously believed. This led them to question the existing concept of the biological value of dietary proteins and also to re-examine the existing recommendations made by the FAO and WHO for protein intakes in healthy subjects. In individuals aged between 56 and 80, recommended values were found to be at least 25% too low. In the case of children with burns, the group showed an enhanced rate of protein synthesis and breakdown implying a protein requirement far greater than the recommended amount for healthy individuals. Turning to individual amino acids, Prof. Young’s group showed that plasma levels responded to changes in dietary supply.
Studies on tryptophan, threonine, valine and lysine showed that plasma responses are sensitive indicators of the point at which amino acid concentrations become marginal or even inadequate to sustain normal rates of protein turnover. Analyzing published studies of such obligatory nitrogen losses and of whole body turnover convinced Prof. Young’s group that existing recommendations for amino acid requirements were too low. His own studies of 13C-labelled amino acid turnover confirmed this view. They calculated that the minimum requirement for indispensable amino acids for adults was 2-3 times higher than current FAO/WHO recommendations.
Vernon Young also developed novel biochemical techniques and non-invasive methods for the study of protein turnover in skeletal muscle. Much of his group’s pioneering work was on the use of stable isotope probes such as 15N, 2H, 18O and 13C for the study of nitrogen metabolism in premature infants and in children with burns as well as for determining quantitative amino-acid needs in older individuals. Prof. Young’s group also developed a method for assessing muscle protein turnover by measuring the daily urinary output of 3-methylhistidine. This remains the only non-invasive method for the assessment of muscle protein degradation in man.
Prof. Young’s research also extended to the study of the metabolism of iron, zinc, copper and selenium in man. In collaboration with M. Janghorbani, the group developed methods for measuring the stable isotopes of these metals in blood, urine and feces.
They found that separate mechanisms exist for the absorption of zinc and copper and that the absorption rate increases following dietary restriction. Extending the technique to selenium gave a valuable measure of the turnover of this element.
In addition, a major interest of Pr. Young’s research team was the question of protein quality. Their research concluded, amongst other things, that soybean proteins could serve as the sole source of nitrogen and essential amino acids. This work did much to encourage the adoption of a method of assessing the nutritional value of food proteins based on estimates of amino acid requirements in the United States.