Reviews and Information for Leucine
Muscle & Workout Supplements (Creatine and BCAAs)
Find the best muscle and workout supplements with creatine and branched-chain amino acids (BCAAs), tests for contamination with dicyandiamide, evidence for increasing muscle strength and endurance, improving your workout, dosage, safety, side effects and more. Find out which ones passed or failed our tests and why.
Muscle & Workout Supplements (Creatine and BCAAs) Review
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Product Review
Protein Powders and Shakes Review
Find Out Which Protein Products Passed or Failed Our Tests
Product Review
Olive Leaf Extract Supplements Review
Learn What Olive Leaf Does and the Best Brands
Product Review
Lion's Mane and Chaga Supplements Review
Read Labels Carefully -- Many Can Mislead
Product Review
Electrolytes & Sports Drinks Review
See Which Sports Drinks, Powders, and Pills Deliver the Right Electrolytes
Product Review
Lavender and Tea Tree Essential Oils Review
Oils Tested for Authenticity and Purity
Product Review
Multivitamin and Multimineral Supplements Review
32% Failed our Tests. Choose Your Multivitamin Carefully.
CL Answer
Do essential amino acid (EAA) supplements help build muscle better than dietary protein or protein supplements?
Comparison of essential amino acids vs dietary protein and protein supplements for building muscle.
Clinical Update
1/24/2016
Leucine Protects Muscle In Middle-Aged
A recent study found that active, middle-aged people restricted to bed rest for several days lost significantly less muscle mass and function if given a leucine supplement along with their meals. Fat gain was also reduced. Get the details, including our tests of leucine-containing supplements, in the Muscle Enhancers Review >>
Product Review
Red Yeast Rice Supplements Review
Only 2 of 7 Red Yeast Rice Supplements Approved in CL Tests
Product Review
Probiotic Supplements Review (Including Pet Probiotics)
See What's Really in Probiotics and Our Top Picks
Clinical Update
9/15/2020
Preventing Muscle Loss with Leucine?
Do supplements with leucine (a branched-chain amino acid or BCAA) prevent muscle loss when muscles are immobilized (such as in a leg brace)? See what a recent study showed in the What It Does section of our Muscle & Workout Supplements Review.
Clinical Update
2/23/2022
Leucine for Muscle Loss?
Did leucine supplementation improve physical function in people ages 70 and older with age-related muscle loss in a recent study? Find out in the Branched-chain amino acids (BCAAs) section of our Muscle & Workout Supplements Review.
Also see our answer to the question: Which vitamins and minerals should someone over 70 take?
Clinical Update
1/26/2026
Leucine to Prevent Muscle Loss?
Can leucine prevent muscle loss when you’re immobilized? Find out in our Muscle & Workout Supplements Review, which includes our Top Picks for BCAAs and creatine.
Product Review
NAC (N-Acetyl Cysteine) Supplements Review
Choose the Best NAC Supplement and Save Money
Product Review
Glutathione Supplements Review
Learn How Glutathione Products Differ, Which Failed, and Our Top Picks
Product Review
L-Lysine Supplements Review
Read L-Lysine Labels Carefully. Some Can Fool You.
Product Review
PQQ (Pyrroloquinoline Quinone) Supplements Review
Learn What PQQ Does and Which PQQ Supplements are Best
Product Review
Resveratrol Supplements Review (From Red Wine, Knotweed, and Other Sources)
See Which Resveratrol Supplements Were Best In Our Tests and Comparisons. Learn What Resveratrol Can and Can't Do.
Product Review
Weight Loss Supplements Review (7-Keto DHEA, Forskolin and Stimulant Blend Supplements)
Choose the Best Weight Loss Supplement. Be Careful With Weight Loss Supplements — Few Pass Quality Testing and Safety Review.
Product Review
Berberine and Goldenseal Supplements Review
Tests Reveal the Best and Worst Berberine and Goldenseal Products
Product Review
Zinc Supplements, Lozenges, and Melts Review
Find the Best Zinc Supplements, Including Lozenges for Colds.
Product Review
DHEA Supplements Review
Beware of Differences in Dose and Price.
Product Review
Iron Supplements Review (Iron Pills, Liquids and Chews)
See Which Iron Supplements Are CL's Top Picks for Different Needs
CL Answer
What’s the Best Way to Get High-Quality Protein from Food?
Find out the best way to get high-quality protein from animal or plant-based food instead of supplements.
CL Answer
Best Supplements to Prevent Age-Related Muscle Loss
Discover the top supplements to prevent age-related muscle loss after 60. Learn how protein, fish oil, vitamin D, and more can help maintain muscle strength and combat sarcopenia.
Product Review
Turmeric and Curcumin Supplements and Spices Review
See Our Top Picks Among Turmeric Products
Product Review
Magnesium Supplements Review (Including Calcium, Vitamins D & K, and Boron)
Find Out What Magnesium Does, Who Needs It, and Our Top Picks Among Supplements
CL Answer
Does Alpha Brain really improve memory, focus and cognition?
Find out if Alpha Brain really improves memory, focus and cognition. See the clinical evidence and get details about Alpha Brain ingredients, as well as potential side effects and drug interactions. ConsumerLab.com's answer explains.
CL Answer
Which supplements may benefit people with essential tremor, and which should be avoided?
Learn about supplements used for treating essential tremor, including caprylic acid (also called octanoic acid), thiamin (vitamin B1), cannabidiol (CBD), GABA (gamma-aminobutyric acid), and branched-chain amino acids. Find out which work and which don't. Also find out which supplements and food may make essential tremors worse.
Recalls & Warnings
December 15, 2025
Genepro Whey 4th Generation Protein Recalled Due to Allergen Risk
On November 12, 2025, Genepro Protein, Inc. recalled Genepro Whey 4th Generation Plasma Treated Protein (unflavored) because the product is mislabeled and fails to declare milk as an allergen.
Recalls & Warnings
April 29, 2014
Seller of B Vitamins, CoQ10, Amino Acids and Other Supplements Warned for Manufacturing Violations and Drug Claims
On April 1, 2014, the FDA issued a warning letter to Bio-Recovery, Inc.
