Dietary Reference Intakes for the micronutrients: considerations for physical activity.

The Dietary Reference Intakes (DRIs) are a set of recommendations for healthy persons. For the most part, recommendations are determined experimentally under controlled conditions of light activity. During increased physical activity, it is expected that micronutrient requirements would increase relative to the inactive state. Micronutrients of interest to athletes are those associated with oxygen handling and delivery, such as iron, and vitamin D, a newly emerging function of which is to maintain muscle strength. The DRI report on electrolytes (including water) is the most recent set of recommendations. In addition to recommendations for intakes to meet needs, many micronutrients have an upper level that indicates caution in consuming a large amount. We illustrate the process of setting DRI values for the micronutrients (including electrolytes and water), and provide a summary of instances where physical activity needs were considered when DRI values were derived. Understanding the origin of DRI values for micronutrients will assist in understanding how to use the values in assessment and planning.

High-performance liquid chromatographic assay of lactic, pyruvic and acetic acids and lactic acid stereoisomers in calf feces, rumen fluid and urine.

To facilitate clinical investigation of metabolic acidosis, a high-performance liquid chromatographic method was adapted and validated for the chiral separation of D-(-) and L-(+)-lactic acid in calf feces, rumen fluid and urine. A non-chiral method was also adapted and validated for the separation of pyruvic, acetic and DL-(+/-)-lactic acids in calf feces and DL-(+/-)-lactic and pyruvic acids in rumen fluid. Separation and quantification were achieved using a reversed phase sulphonated polystyrenedivinylbenzene analytical column for pyruvic, acetic and racemic lactic acids and by a 3 microm octadecylsilane (ODS) packed analytical column coated with N,N-dioctyl-L-alanine as the chiral selector for the separation of lactic acid enantiomers with Cu(II)-containing eluents by stereoselective ligand exchange chromatography. Endogenous analytes were present in validation samples over a range of concentrations (0.2-14.8 mmol/l). For the stereoselective assay, mean intra-day accuracy ranged from 90.6 to 108.4% and intra-day precision from 0.3 to 13.8%. For the non-stereoselective assay, mean intra-day accuracy ranged from 90.4 to 108.8% and intra-day precision from 1.5 to 11.1%. The limit of quantitation was 1.0 mmol/l for D- and L-lactic acid, 0.06125 mmol/l for pyruvic acid, 1.0 mmol/l for DL-lactic acid and 1 mmol/l for acetic acid. These assays can be used to study the role of the gastrointestinal tract and kidney in metabolic acidosis.