Optimal intakes of protein in the human diet

For protein, progress is slow in defining quantifiable indicators of adequa cy other than balance and growth. As far as current requirements are concer ned, only in the case of infants and children is there any case for revisio n, and this change is to lower values. Such intakes would appear to be safe when consumed as milk formula. In pregnancy, notwithstanding the concern t hat deficiency may influence programming of disease in later life, there is little evidence of any increased need, and some evidence that increased in takes would pose a risk. For the elderly there is no evidence of an increas ed requirement or of benefit from increased intakes, except possibly for bo ne health. For adults, while we now know much more about metabolic adaptati on to varying intakes, there would appear to be no case for a change in cur rent recommendations. As far as risks and benefits of high intakes are conc erned, there is now only a weak case for risk for renal function. For bone health the established views of risk of high protein intakes are not suppor ted by newly-emerging data, with benefit indicated in the elderly. There is also circumstantial evidence for benefit on blood pressure and stroke mort ality. With athletes there is little evidence of benefit of increased intak es in terms of performance, with older literature suggesting an adverse inf luence. Thus, given that a safe upper limit is currently defined as twice t he reference nutrient intake, and that for individuals with high energy req uirements this value (1.5 g/kg per d) is easily exceeded, there is a case f or revising the definition of a safe upper limit.