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The essential amino acid guide

EAA supplements: what the research says

Essential amino acids (EAAs) are the nine amino acids your body cannot make. In studies they are the part of protein that switches on muscle protein synthesis. This guide covers what EAAs may and may not do, the doses researchers used, and how to read a label, with every claim linked to its source.

1LLeuLeucine2IIleIsoleucine3VValValine4KLysLysine5MMetMethionine6FPhePhenylalanine7TThrThreonine8WTrpTryptophan9HHisHistidine
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Skeletal structure of leucine, showing the amino group, the acid group and the branched side chainPLATE 02 LEUCINE, C6H13NO2NH2OOHBRANCHED SIDE CHAINAMINO GROUPACID GROUPα
Fig. 1 Leucine, the most studied of the nine. Every amino acid shares an amino group and an acid group; the side chain sets each one apart.
01 Start here

Three questions most people ask first

Is an EAA worth it, how does it compare with BCAAs and whey, and how much do studies use? Start with whichever fits.

Buying guide01Choose an EAAWhat to look for on the label, which brands sell what, and who EAAs suit.Read the guide Comparison02EAA vs BCAAWhy three amino acids are not the whole story, with the research.Read the guide Dosage03How much to takeThe doses studies used, leucine content, and how to read the grams.Read the guide
02 What we know

The evidence in three lines

What the studies we cite actually measured, in plain language.

  1. EAAs drive the signal

    In older adults, 18 g of EAAs raised muscle protein balance as much as 40 g of mixed amino acids (Volpi 2003). Non-essential amino acids added little.

  2. BCAAs alone fall short

    Building muscle protein needs all nine. A review found no human study of oral BCAAs alone measuring a rise in muscle protein synthesis (Wolfe 2017).

  3. Total protein matters most

    For muscle size, total daily protein predicted results better than timing (Schoenfeld 2013). EAAs are one way to add to it.

03 Finder

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3 What matters most

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04 The science

How EAAs compare

Protein foods differ in how much of their protein is essential. Animal proteins tend to run higher than many plant proteins.

Bar chart of essential amino acids as a percent of protein: whey 43, milk 39, muscle 38, casein 34, egg 32, wheat 22, oat 21, lupin 21 (Gorissen 2018)PLATE 11 ESSENTIAL AMINO ACIDS, % OF PROTEIN01020304050Whey43.0Milk39.0Muscle38.0Casein34.0Egg32.0Wheat22.0Oat21.0Lupin21.0SOURCE: GORISSEN ET AL. 2018ANIMALPLANTMUSCLE
Fig. 2 Essential amino acids as a percent of protein, from Gorissen et al. 2018.

Why it matters. The ISSN position stand on protein says it is the EAAs that are required to stimulate muscle protein synthesis, and that rapidly digested proteins high in EAAs and leucine are most effective at doing so.

Where supplements fit. An EAA powder is all essential amino acids, so a small scoop delivers what a larger serving of food protein would. That can help when appetite is low or calories are tight. EAA vs whey protein.

Leucine. Leucine appears to act as a trigger for muscle protein synthesis, especially in older adults (systematic review, 2021). All nine EAAs explained.

05 Learn

The science, page by page

Benefits, dosing, timing and safety, each with the studies behind it.

The nine essential amino acids drawn as element tiles, with the three branched-chain amino acids highlightedPLATE 01 THE NINE ESSENTIAL AMINO ACIDS 1 L Leu Leucine 2 I Ile Isoleucine 3 V Val Valine 4 K Lys Lysine 5 M Met Methionine 6 F Phe Phenylala. 7 T Thr Threonine 8 W Trp Tryptophan 9 H His HistidineBRANCHED-CHAIN (BCAA)OTHER ESSENTIALThe scienceWhat are the 9 essential amino acids?Comparison: an EAA supplement supplies all nine essential amino acids, a BCAA supplement supplies threePLATE 03 EAA VS BCAA 1 L Leu Leucine 2 I Ile Isoleucine 3 V Val Valine 4 K Lys Lysine 5 M Met Methionine 6 F Phe Phenylala. 7 T Thr Threonine 8 W Trp Tryptophan 9 H His Histidine 1 L Leu Leucine 2 I Ile Isoleucine 3 V Val Valine 4 K Lys Lysine 5 M Met Methionine 6 F Phe Phenylala. 7 T Thr Threonine 8 W Trp Tryptophan 9 H His HistidineEAA: ALL 9BCAA: 3 OF 9leucine, isoleucine, valine+ six more essentialsleucine, isoleucine, valineonlyThe scienceEAA vs BCAA: which is better?Comparison of a scoop of whey protein, which contains essential and non-essential amino acids, and a smaller scoop of EAAsPLATE 04 WHEY VS EAA, PER SCOOP WHEY PROTEINEAA POWDERESSENTIALNON-ESSENTIALESSENTIAL ONLYA full protein: all 20 amino acids,plus more calories per servingJust the nine essentials,smaller dose, fewer caloriesPROPORTIONS ILLUSTRATIVEThe scienceEAA vs whey proteinIllustrative curve of muscle protein synthesis rising after an amino acid dose and returning to baseline, not dataPLATE 05 MUSCLE PROTEIN SYNTHESIS, ILLUSTRATIVEBASELINEDOSETIME (HOURS)SYNTHESIS RATESHAPE ONLY, NOT DATAThe scienceEAA benefits: what studies supportAn example supplement facts panel for an EAA powder, showing grams per amino acid, as a layout example onlySupplement FactsServing size 1 scoopAmountEAA blendX gL-LeucineX gL-IsoleucineX gL-ValineX gL-LysineX gL-ThreonineX gL-PhenylalanineX gL-MethionineX gL-HistidineX gL-TryptophanX gOther ingredients: flavors, sweetenerTOTALEAASEXAMPLELAYOUTThe scienceEAA dosage: how much to takeA day timeline with meals, a workout, and the windows where people commonly take EAAsPLATE 06 A DAY, AND WHERE A DOSE FITS6AM9NOON36PM9MEALMEALMEALWORKOUTBEFOREDURINGAFTERDaily protein total matters most; timing is a smaller leverThe scienceWhen to take EAAsA clipboard checklist: pregnancy, kidney or liver conditions, medications, talk to your doctor firstPLATE 07 BEFORE YOU STARTPregnant or nursingKidney conditionLiver conditionTake medicationUnder 18ASK YOUR DOCTOR FIRSTThe scienceEssential amino acid side effects and safety
06 For you

Guides for your situation

Women, older adults, vegans and people who fast each have different questions.

A kettlebell beside a shaker bottle and a scoop of amino acid powderPLATE 08 STRENGTH AND RECOVERY8 KG For youEssential amino acids for womenStairs with a light dumbbell, representing strength and everyday function with agePLATE 09 STRENGTH FOR EVERYDAY LIFEFor youEssential amino acids for older adultsA leaf beside a scoop of plant-based amino acid powderPLATE 10 PLANT-BASED FERMENTED ORPLANT-DERIVEDFor youVegan EAA supplementsA 24 hour clock with a 16 hour fasting window shaded and an 8 hour eating windowPLATE 12 A 16:8 FASTING DAYMIDNIGHT6AMNOON6PMEATFASTFor youDo EAAs break a fast?A row of generic, unbranded supplement tubs in different colorsPLATE 15 MANY LABELS, ONE QUESTION: WHAT IS INSIDE? EAA EAA EAA EAA EAA BrandsEAA brands comparedA generic, unbranded tub of EAA powder with a scoop EAA BrandsKaged EAA and Amino SynergyA generic, unbranded tub of EAA powder with a scoop EAA BrandsTransparent Labs Intra EAAA generic, unbranded tub of EAA powder with a scoop EAA BrandsThorne Amino ComplexA generic bottle of amino acid tablets with loose tablets AMINOTABLETSBrandsBodyHealth PerfectAmino
07 Shop

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08 FAQ

Questions people ask

What is an EAA supplement?

An EAA supplement supplies the nine essential amino acids as free amino acids, usually as a powder or capsules. "Essential" means your body cannot make them, so they must come from food or supplements. The nine are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

Do EAA supplements work?

In short-term lab studies, essential amino acids raise muscle protein synthesis, and studies in older adults suggest they are what drive that response. Long-term results are mixed and small. Most experts see EAAs as a convenient protein source, not a replacement for enough total protein from food.

Are EAAs better than BCAAs?

BCAAs are three of the nine EAAs. Building muscle protein needs all nine, and a 2017 review found no human study showing BCAAs alone raise muscle protein synthesis when taken orally. If you choose one of the two, research favors EAAs.

Are EAAs better than whey protein?

Not necessarily. Whey is a complete protein rich in EAAs, and it costs less per gram of EAA in many cases. EAAs suit people who want a smaller, lower-calorie dose, a drink to sip during training, or an option without dairy.

Are EAA supplements safe?

For healthy adults at the doses used in studies, amino acid supplements are generally well tolerated, but long-term safety data are limited. Talk to your doctor first if you are pregnant or nursing, have a kidney or liver condition, or take medication.

Sources: MedlinePlus, Volpi 2003, Wolfe 2017, ISSN 2017, Gorissen 2018, Schoenfeld 2013. We have not tested these products; see how we choose.