The British journal of nutrition
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Measures of amino acid (AA) digestibility are used widely to estimate bioavailability of AA in feed and food ingredients for monogastric animals. In principle, the digestibility assay is simpler than in vivo assessments of AA bioavailability and allows for simultaneous estimation of the bioavailability of all AA in an experimental diet. It is generally assumed that absorption of intact AA in the hindgut of monogastrics is minimal, even though colonocytes do contain AA transporters and have been shown to absorb AA. ⋯ An implicit assumption when using SID AA coefficients in diet formulation is that the post-absorptive utilization of AA is not influenced by the dietary protein source. This assumption appears inappropriate when using feed or food ingredients that have been over-heated, induce large amounts of EAAL, or contain substantial amounts of fermentable fibre. Improved understanding of processes that contribute to the discrepancy between bioavailability and ileal digestibility will allow a more effective use of AA digestibility coefficients in diet formulation.
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The true ileal digestibility assay provides the most informative measure of digestibility to assess bioavailability of amino acids in foods for humans. To determine 'true' estimates of ileal amino acid digestibility, requires that endogenous amino acids present in digesta at the terminal ileum be quantified. The amounts of endogenous amino acids in ileal digesta can be determined after feeding an animal or human a protein-free diet (traditional approach) or by various methods after giving a protein-containing diet. ⋯ Basal losses should be determined at a defined dry-matter and protein intake. The protein-free diet approach to determining endogenous amino acids is considered unphysiological and basal losses refer to ileal endogenous amino acid flows associated with digesta dry-matter flow, and not including "specific" effects of dietary factors such as non starch polysaccharides and anti nutritional factors. Arguments are advanced that the enzyme hydrolysed protein/ultra filtration method may be suitable for routine application with a cannulated pig model, to obtain physiologically-valid basal estimates of ileal endogenous amino acids to allow calculation of true ileal amino acid digestibility in the pig, and then prediction (via statistical relationships) of true coefficients of amino acid digestibility in humans.
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Review Meta Analysis
Homocysteine-lowering therapy does not lead to reduction in cardiovascular outcomes in chronic kidney disease patients: a meta-analysis of randomised, controlled trials.
The efficacy of homocysteine (Hcy)-lowering therapy in reducing the risk of CVD among patients with chronic kidney disease (CKD) remains controversial. We performed a meta-analysis to determine whether pooling the data from the few small randomised, controlled trials that address this topic would improve the statistical power of the analysis and resolve some of the inconsistencies in the results. Randomised, controlled clinical trials (RCT) were identified from MEDLINE, EMBASE, www.clinicaltrials.gov, the Cochrane Controlled Clinical Trials Register Database and Nephrology Filters. ⋯ The estimated RR were not significantly different for any outcomes, including CHD (RR 1·00, 95 % CI 0·75, 1·31, P = 0·97), CVD (RR 0·94, 95 % CI 0·84, 1·05, P = 0·30), stroke (RR 0·83, 95 % CI 0·57, 1·19, P = 0·31) and all-cause mortality (RR 1·00, 95 % CI 0·92, 1·09, P = 0·98). In the stratified analysis, the estimated RR were not significantly different for cardiovascular events regardless of dialysis or in combination with vitamin B therapy or the degree of reduction in Hcy levels. Our meta-analysis of RCT supports the conclusion that Hcy-lowering therapy was not associated with a significant decrease in the risk for CVD events, stroke and all-cause mortality among patients with CKD.
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Available amino acids are those absorbed from the gastrointestinal tract in a form suitable for body protein synthesis. True ileal digestible amino acids are determined based on the difference between dietary amino acid intake and unabsorbed dietary amino acids at the terminal ileum. The accuracy of ileal digestible amino acid estimates for predicting available amino acid content depends on several factors, including the accuracy of the amino acid analysis procedure. ⋯ Consequently, methionine and cysteine are overestimated if methionine sulphone or cysteic acid are present in the original material. Overall, given the problems associated with the analysis of some amino acids in processed foodstuffs, the available amino acid content may not always be accurately predicted by true ileal amino acid digestibility estimates. For such amino acids specific analytical strategies may be required.
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Cereals and legumes are staple foods in India and are limiting in lysine and sulphur amino acids, respectively. Available lysine loss, due to Maillard-type reactions that may occur during food preparation, exacerbates the problem of lysine deficiency particularly in cereals. Consequently, determining the contents of digestible essential amino acids, particularly lysine, is important. ⋯ True ileal amino acid digestibility varied widely both across ingredients and prepared foods for each amino acid (on average 60-92 %) and across amino acids within each ingredient and prepared food (overall digestibility 31-96 %). Amino acid digestibility was low for many of the ingredients and prepared foods and consequently digestibility must be considered when assessing the protein quality of poorer quality foods. Given commonly encountered daily energy intakes for members of the Indian population, it is estimated that lysine is limiting for adults in many Indian diets.