Branched-Chain Amino Acids (BCAAs)

An umbrella review inherits the primary trials' limitations and cannot fix them, and moderate certainty still means the true effect may differ substantially from the estimate. No pooled effect sizes appear, only the gradings, so nothing here says how big the reduction is. Searches ran only to May 2022.

Low certainty for the encephalopathy benefit, very low for everything else, which is as much the finding as the numbers. No trial compared these preparations against lactulose or rifaximin, the drugs these patients actually get, so nothing here says whether they add to standard care.

This measures what was in the blood, not whether anyone took a supplement, so a powder started after the draw would be invisible. The intervals are wide enough to include modest risk either way, leucine running from 0.57 to 1.33. Estimates below 1 are not evidence of protection.

Only five of twelve studies could be pooled, and the main analysis compares before with after inside the supplemented group rather than against a control, so it cannot separate the supplement from everything else that changed. Cirrhosis is a malnourished state. None of this transfers to a well-fed person.

Ten trials is a small base, and the review reports no pooled effect size at all. Soreness is self-reported. The dose ceiling is where the evidence stops, not where a harm begins, and the review is explicit that it cannot speak to anything above it.

A food-composition database, not a study: it says how much is in what, and nothing about what these amino acids do. Values are averages across sampled products and shift with cut, brand and cooking loss. The figures are per 100 g, not per portion.

Ten men, one four-hour window, and all of them already trained. The comparator was placebo, so this shows branched-chain amino acids beat nothing rather than that they match protein. The authors put the rise at roughly half what intact protein produces in similar designs, which this study never measured directly.

An overview of reviews inherits every weakness of the trials underneath it, and the same small primary studies are counted inside several of the eleven. The authors grade those reviews and report the recurring flaws: no justification for excluding studies, and no funding disclosure for the primary trials.

Fifteen men per group, healthy and aged around 71, at rest with no exercise. The doses are not matched: 6 g of branched-chain amino acids against 30 g of milk protein is the choice a shopper faces, not a gram-for-gram test of which does more. Nothing here was measured beyond five hours.

The abstract never says how many men took part, which is the first thing you would want from a dose-response study. The adverse signal is a blood chemistry change, not a symptom anyone reported. Healthy young men, fed briefly, so nothing here reaches long-term intake.

Nine trials is a small pool and the searches ended in December 2013, so a decade of later work is missing. The two outcomes are measured on different clocks: synthesis takes hours, lean mass takes weeks to months, so part of the contrast is a contrast of study durations. Older adults only.

Eight men per arm, one acute measurement, nothing past four and a half hours and nothing on muscle size. Part-funded and co-authored with a commercial protein-beverage research centre, a direct interest in a result about beverage formulation. A fifth arm added isoleucine and valine, and its value was never published.

Ten men, one four-hour window, no size or strength endpoint. A p value of .039 and an interval running from -0.002 to 0.028 do not agree, and the interval is the more cautious reading. Same laboratory and near-identical design to the same group's 2017 trial, so the two are not independent.

Genetic proxies for circulating levels are not a stand-in for swallowing a supplement, and neither study gave anyone one. Both draw on European-ancestry samples, and the UK Biobank cohort is healthier than the general population. Neither rules out a smaller effect running the other way.

Soreness is self-reported on a visual scale, and it is a symptom rather than a measure of recovery or performance. The abstract reports no publication-bias check, no risk-of-bias grading and no funding disclosure for the trials pooled, in a field where manufacturers fund much of the primary work.

How much BCAAs ease soreness is unsettled. The largest estimate rests on the thinnest base, never checked for publication bias, while three more careful syntheses of the same question land smaller.

No point estimates or confidence intervals appear for either direction, so the size of this is unknown. Genetic proxies for circulating amounts are not a test of taking a supplement. Exposure and outcome samples overlap, which can pull the estimate towards the plain observed association.

Tested in one direction, high blood branched-chain amino acids look like a result of poor metabolic health; tested in reverse, like a cause of worse blood fats. No effect size was given for either, so how much each matters is open.

Fourteen of the 35 trials carried some risk of bias, and the authors report high heterogeneity. Older adults, many of them at risk of undernutrition, so the baseline protein intake is not a well-fed lifter's. Physical performance sat exactly on the significance line, an interval starting at zero.

These numbers come from a programme run under the International Council on Amino Acid Science, a nonprofit funded by the amino acid industry. The review says so itself. Short-term trials in healthy adults only, so nothing about long-term intake or about people with liver or kidney disease.