EAAs: What They Actually Do, the Dose, and Whether They Are Worth It

A practical breakdown of what EAAs do in muscle, how many grams and when to take them, and the cases where regular protein makes them pointless.

EAAs are the nine essential amino acids your body cannot build on its own, so they have to come from food or a powder. Marketing sells them as a separate tool, but they are just the pieces of the protein you already ate at lunch. The question is not whether they work, it is whether you need them apart from normal eating.

What EAAs actually do

Muscle protein synthesis ramps up when blood levels of essential amino acids spike, and most of that signal is carried by leucine. Your body makes the non-essential ones on its own, so they are not the bottleneck. The practical leucine threshold per feeding is about 2.5–3 g for people under 40 and 3–4 g for people over 60, because muscle gets less responsive to the same signal with age.

The response starts 30–45 minutes after intake, peaks around 90 minutes, and is back to baseline within 3 hours. That points to one thing worth remembering: EAAs do not build muscle by themselves. They raise a signal. Without resistance training and enough total calories and protein, the effect is trivial.

EAAs, BCAAs, and food protein

BCAAs are only 3 of those 9 amino acids (leucine, isoleucine, valine). They raise the signal but leave out the other 6 building blocks, so the response is weaker and shorter than with the full spectrum. If the choice is BCAAs or EAAs, take EAAs. If the choice is EAAs or regular protein, the math usually favours protein.

25 g of whey gives roughly 11–12 g of EAAs and about 2.7 g of leucine.
150 g of cooked chicken breast gives about 45 g of protein and roughly 3.4 g of leucine.
3 large eggs give about 19 g of protein and about 1.5 g of leucine, which is under the threshold.
A 10 g scoop of EAA powder gives about 10 g of EAAs and 2.5 g of leucine, but usually costs 2–4 times more per gram of leucine.

If you can eat a meal, the meal wins almost every time. EAAs solve the case where a meal is not an option.

Dose: how much and when

10–15 g of EAAs per serving, with at least 2.5–3 g of leucine. Servings of 5–6 g are marginal and mostly wasted.
If you train fasted, take one serving 15–30 minutes before or during the first third of the session.
One to two servings a day, maximum. Beyond that you are just paying a premium to replace food.
Total protein is still the main lever: 1.6–2.2 g per kilogram of body weight per day, spread over 4 meals of roughly 0.4 g/kg, every 3–4 hours.
If your session is under 90 minutes and you ate a meal with 30+ g of protein in the last 2–3 hours, an extra serving adds nothing.

When they genuinely make sense

A 6 a.m. fasted session when you physically cannot eat before lifting.
Poor appetite from illness, stress, or an aggressive 500 kcal deficit, when you keep landing below 1.6 g/kg from food.
Immobilisation: a cast, post-surgery, 2–3 weeks without loading that leg. Two servings a day here help slow muscle loss.
People over 65 who eat 2 small meals a day and rarely hit the leucine threshold.
Unplanned plant-based eating, where meals run low in leucine and lysine.

When they are a waste of money

If you already hit 1.6–2.2 g/kg of protein, another 10 g of EAAs will not add measurable muscle. They do not burn fat, do not fix joints, and do not meaningfully reduce next-day soreness. The idea that you need to sip something through every session or you go catabolic does not hold for 45–75 minute workouts.

Safety and side effects

In healthy people, up to 15–20 g a day is well tolerated. Larger doses on an empty stomach can cause nausea, bloating, and loose stools. The taste is rough, so products get heavy sweetener loads that upset some stomachs. Supplements are not regulated like medication, so it is worth picking something with independent lab testing of the label.

When to see a doctor

Chronic kidney or liver disease, or elevated creatinine on a blood panel. Do not start EAAs on your own.
Phenylketonuria or another metabolic disorder, since EAAs contain phenylalanine.
Pregnancy and breastfeeding.
Levodopa therapy, because amino acids reduce its absorption, and unstable insulin-treated diabetes.
Unintentional loss of more than 5% of body weight in 6 months, or losing strength despite 8–12 weeks of consistent training.

The short version

EAAs raise muscle protein synthesis through leucine, but build nothing without training and enough total protein.
The working dose is 10–15 g with 2.5–3 g of leucine, once or twice a day at most.
25 g of whey or 150 g of chicken does the same job, usually for less money.
They earn their place for fasted training, poor appetite, immobilisation, and older adults.
Kidneys, liver, PKU, pregnancy, and levodopa are reasons to ask a doctor first.