diet medical National Center for Biotechnology Information NCBI NLM MEDLINE review humans pubmed abstract nih national institutes of health national library of medicine dietary supplements vitamins / administration & dosage body composition / physiology United States practice guideline societies environment fluid therapy altitude dietary proteins / administration & dosage dietary fats / administration & dosage energy metabolism / physiology physical endurance / physiology investigators=[] affs=[]) athletic performance / physiology* pmid:19225360 doi:10.1249/mss.0b013e31890eb86 collabauthor(name='american dietetic association' collabauthor(name='dietitians of canada' susie langley amino acids / administration & dosage vegetarian muscle strength / physiology nutritional requirements* physical education and training trace elements / administration & dosage