Essential amino acids (EAA)

The amino acids the body cannot make, in a small scoop. A reasonable second choice for people whose meals fall short of protein and who cannot take a protein powder, including many on weight-loss injections.

At a glance

Our verdict	Second line, only when meals fall short and you cannot take whey or another protein powder.
Best use	Protein when powders are not tolerated
How sure the evidence is	Low for muscle outcomes (tiny trials)
Cost a month	About $70 to $75 at 1 serving a day; $140 to $150 at 2

Written for adults in Canada. It explains the evidence; it is not advice for you personally. Last reviewed 20 October 2026.

Supplement Check

Is it right for you?

EAA only make sense if your meals fall short of protein and a powder does not suit you. Your check works out both, and checks your kidneys, levodopa and rare inherited conditions first. Our Supplement Check looks at:

Phenylketonuria or maple syrup urine disease: never
Kidney disease, kidney stones, kidney function below normal (eGFR under 60), or kidney function not known
Severe liver disease or hepatic encephalopathy
Pregnancy and breastfeeding
Cancer under treatment
Every medicine you take

Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.

$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check

Tell me when it opens

What it is

Free-form essential amino acids: leucine, isoleucine, valine, lysine, threonine, methionine, phenylalanine, histidine and tryptophan, usually with extra leucine. They are the parts of protein the body cannot make.

The product in our review: an essential amino acid powder licensed by Health Canada (your report names it). One serving gives about 3.8 g of essential amino acids, including 1,250 mg of leucine; the licensed dose for adults is 1 serving once or twice a day. Retail listings describe it as NSF Certified for Sport; we confirm that on the register at each order. Other licensed EAA powders exist in Canada, but we found no third-party testing or published contaminant results for them.

Structure of Essential amino acids (EAA) — Structure: PubChem (public domain).

How it acts

Muscle building after a meal is driven by the essential amino acids, with leucine as the trigger. About 20 g of whey (about 8.6 g of essential amino acids) gives the most muscle building after exercise in young men. Free amino acids are absorbed fast and give a sharp rise in the blood from a small dose, and muscle building follows that peak. [1] Whole protein and mixed meals give a longer response and also supply the non-essential amino acids. [2] This explains why a small dose can match whey in the short term; it is not proof of more muscle over months.

Diagram: how Essential amino acids (EAA) acts

Outline of a person showing where Essential amino acids (EAA) acts in the body

What it is used for, and what the evidence says

Used to support muscle building when whole protein cannot be eaten in enough quantity. Most of the evidence measures muscle building over a few hours, not muscle or strength over months.

Use	What the trials found	How sure we are
Muscle building over a few hours, older women	3 g of leucine-rich EAA stimulated muscle building as much as 20 g of whey, at rest and after exercise; [3] 1.5 g and 6 g were similar to 40 g of whey over the first 2 hours, though whey and the 6 g dose lasted longer. [4] About 8 people a group.	Low
Lean mass over 3 months, older women	15 g of EAA a day raised lean body mass; strength did not change. 7 people a group. [5]	Low
Young adults	An EAA-plus-whey mix gave 3 to 6 times the whole-body protein balance per gram of a whey drink; the authors were linked to industry, and this was whole body, not muscle. [6]	Low
Leucine on its own	9 trials in older people: muscle building rose but lean body mass did not. [7] Whey beat leucine-matched collagen for muscle size over 10 weeks. [8] Leucine without the other amino acids, or without enough protein overall, does not build muscle.	Moderate (no lean mass)
Eating too little (energy deficit)	Whey with added EAA kept muscle building up after exercise while underfed, where whey with carbohydrate did not. [9] A review suggests EAA may protect muscle building better than whole protein in deficit. [2]	Low
People on GLP-1 weight-loss medicines	No trial. A 2026 review calls EAA an add-on supported only indirectly. [10]	No evidence (no trial)
Head to head with whey over months	No trial of EAA against whey for lean mass over months. Leucine-matched pea or soy protein did match whey over 12 weeks, [11] which is why a plant powder comes before EAA.	No evidence (no trial)

How sure we are: High means further research is very unlikely to change the answer; Moderate, it might; Low, it may well change; Very low, we are very unsure. These follow the GRADE method that guideline panels use.

Benefits

Short-term muscle building equal to whey from a much smaller dose (low certainty). [3]
A small gain in lean mass in one 14-person trial; no strength gain shown (low certainty). [5] For comparison, whole protein with training adds about 0.3 kg of lean mass. [12]
Small volume and not filling: useful when a powder makes you feel too full or sick, as is common on weight-loss injections.

Risks and side effects

Bitter taste; nausea at larger doses.
Far less protein: one serving is about 4 g of amino acids against about 20 g in a scoop of whey. It does not replace eating enough protein.
Less filling than whole protein: an advantage on weight-loss injections, a disadvantage for appetite control.
High blood levels of branched-chain amino acids go with insulin resistance in population studies (an association only, not proof of harm).

Interactions with medicines

EAA do not change how the liver clears medicines: no enzyme induction or inhibition is known. The one interaction that matters is with levodopa.

Medicine	What can happen	What to do
Levodopa (carbidopa-levodopa, Sinemet, Duodopa, benserazide-levodopa)	Amino acids compete with levodopa for absorption and entry into the brain (the same applies to whey and high-protein meals)	Take levodopa at least 30 to 60 minutes before; your prescriber sets the timing
Medicines that act on serotonin	The tryptophan content (20 mg) is too small to matter	None

Who should not take it

Phenylketonuria or maple syrup urine disease: never.
Kidney disease, kidney stones, kidney function below normal (eGFR under 60), or kidney function not known: held, as for protein powder; the protein target is set by a doctor or kidney dietitian.
Severe liver disease or hepatic encephalopathy: the doctor decides.
Pregnancy and breastfeeding: no data; food protein instead.
Cancer under treatment: no specific concern found; the oncology dietitian decides.
Not as a first choice: meals first, then whey, then a leucine-matched pea or soy powder.
Drug-tested athletes. We ask by example, because few people know the term: a national or provincial team, carded athlete or Canada Games; university or college sport (U SPORTS, the CCAA, NCAA); junior hockey (QMJHL, OHL, WHL); a professional or minor-professional league (AHL, ECHL and others); or anyone told they can be tested. “Not sure” counts as yes. Then only a product on the NSF Certified for Sport or Informed Sport register, batch-tested, and the report goes to Dr. French before release.
Under 18: outside the Supplement Check.

Dose and timing

Who: fewer than 3 protein meals a day, and whey and plant powders do not suit you (milk allergy, whey upsets your stomach and plant powders do too), or powders make you feel too full or sick.
Dose, as on the label: The product, 1 serving once or twice a day, with or between meals, and after strength exercise. Two servings give about 7.6 g of essential amino acids and 2.5 g of leucine.
Trials used from 3 g of leucine-rich EAA in a single dose up to 15 g of EAA a day; [3, 5] our earlier review suggested 10 to 15 g a day. We use the licensed label dose and do not go above it.
Always with strength exercise on 2 or more days a week: that is what keeps muscle.
Store dry, sealed, at room temperature.
How to tell it is working: protein intake reaching the target on a 3-day food record; grip strength and body composition steady or rising at 8 to 12 weeks with training; you tolerate it.

What we know about Canadians

No Canadian data on EAA use in our review. On protein in general: Canadian adults eat about 80 g of protein a day on average, two-thirds of it from animal foods, and few fall below the official requirement; the group most often below it is women over 70, at about 1 in 10. [13] No Canadian survey has reported how many fall below the higher targets now advised for older adults.

Canada has no count of people on GLP-1 medicines, but public drug plans spent $807 million on semaglutide in 2024, the single largest driver of growth in public drug spending. [14]

Most at risk of eating too little protein: women over 70, people with a poor appetite or living alone, people losing weight (including on GLP-1 medicines), and plant-only diets.

How sure are we: moderate. National nutrition survey (2015) for the official requirement; no Canadian data for EAA use or for the higher protein targets.

An honest comparison: muscle when meals fall short of protein

Same outcome, cost a month in Canadian dollars.

Option	Effect	How sure we are	Cost a month (CAD)
Whey isolate 20 to 30 g a day	+0.30 kg lean mass and +2.49 kg strength with training [12]	Moderate	About $39
Leucine-matched pea or soy isolate	Same lean mass (+1.54 kg in both groups) and strength as whey over 12 weeks [11]	Low to Moderate	About $35 to $50
EAA powder, 1 to 2 servings a day	Short-term muscle building equal to whey; lean mass up, strength not, in one tiny trial [3, 5]	Low	About $70 to $150
Strength training, 2 to 3 days a week	About +0.8 to +1.1 kg of lean mass [15, 16]	Moderate	$0 to $60
Food protein at every meal	The reference: what the target is built on	Moderate	Food
None	No medicine is approved to keep or build muscle	—	—

Read honestly: strength training does the most, food protein comes next, and a powder only fills a gap. EAA cost the most per gram of protein and have the thinnest evidence, which is why they come last.

Our verdict

Recommended only for adults whose meals fall short of the protein target and who cannot take whey or a plant protein powder, or who find a powder too filling (common on weight-loss injections). Always alongside strength exercise.

Not for anyone with phenylketonuria or maple syrup urine disease, and held for kidney disease or unknown kidney function. On levodopa, take it at least 30 minutes before the amino acids.

Dr. French's ruling: if a person cannot tolerate whey or other protein powders, offer essential amino acids instead. The evidence supports that as a second line: a small dose matches whey for muscle building over a few hours, but the trials are tiny, measure short-term building rather than muscle over months, and show no strength gain. A leucine-matched pea or soy powder gave the same muscle and strength as whey over 12 weeks and supplies more protein for less money, so it comes first. Strength training is what keeps muscle; amino acids only support it.