What are BCAAs? The 9 essential amino acids, EAA, glutamine, and whether you need them with whey

BCAAs are the three branched-chain amino acids: leucine, isoleucine and valine. All three belong to the 9 essential amino acids the body cannot make and must get from food. People who already eat enough protein over the day, from food and whey for example, get their BCAAs in it, and there is little evidence that a separate BCAA supplement adds more. This page explains EAAs, BCAAs and glutamine as the research reports them.

What are essential amino acids?

Proteins are built from amino acids. MedlinePlus, from the U.S. National Library of Medicine, sorts them into three groups: essential amino acids cannot be made by the body; nonessential ones the body can make even if they are not in the diet; and conditionally essential ones are usually not essential but become essential during illness and stress.

The 9 essential amino acids are:

Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine

MedlinePlus says you do not need to eat all of them at every meal; what matters is getting a balance over the whole day.

BCAA vs EAA

EAAs (essential amino acids) are all 9 essential amino acids; BCAAs are the 3 of them with a branched structure. Leucine gets the most attention because it signals muscle to start building protein.

A 2017 review by Wolfe in the ISSN's journal explains that muscle protein synthesis is limited by having all the essential amino acids available, so taking only BCAAs cannot create an anabolic state in theory: the signal is not enough if the other 6 building blocks are missing. Wolfe found only 2 human studies of BCAAs alone, both given intravenously, and in both muscle protein synthesis and breakdown fell, with the breakdown state persisting throughout. He found no human studies of BCAAs taken alone by mouth. His conclusion is that BCAA supplements alone do not promote muscle building. Leucine alone has a limit too: as leucine rises, blood valine and isoleucine fall.

The ISSN's protein position stand (Jäger and colleagues, 2017) says about 6–15 g of EAAs stimulates muscle protein synthesis, with about 10 g as a rough optimum, and that leucine should not be taken alone, because balanced EAAs give the largest effect.

Whey already contains BCAAs and EAAs

The ISSN says whey and casein are high in leucine and that whey digests fast. The proteins that work best for muscle building are rapidly digested, high in essential amino acids and contain enough leucine. Each meal should provide about 20–40 g of protein with 700–3,000 mg of leucine, and total daily protein should be about 1.4–2.0 g per kg of body weight.

A study cited by Wolfe shows the difference clearly: adding 5 g of BCAAs to 6.25 g of whey gave a result comparable to 25 g of whey, because whole protein supplies every essential amino acid. If you already get enough protein, the extra money spent on BCAAs brings back little. Compare protein value with the price-per-gram calculator and see every whey brand.

What is glutamine, and does it help muscle?

L-glutamine is an amino acid the body can make itself; MedlinePlus also lists it as conditionally essential. A systematic review and meta-analysis in Clinical Nutrition (2019) gathered 47 studies and pooled 25 of them. It concluded that, overall, glutamine had no effect on athletes' immune system, aerobic performance or body composition, so the evidence that it builds muscle is weak.

When to take BCAAs

We found no study we could verify showing a best time for BCAAs. What has evidence is total daily protein split into meals of 20–40 g; the method is in how and when to take whey. If you already take BCAAs or EAAs, treat them as an add-on to a protein meal, not a replacement. See amino acids in our store.

Who should be careful

RxList, citing the Natural Medicines database, lists these precautions for BCAAs:

Pregnancy or breastfeeding: not enough safety information, so avoid
ALS (amyotrophic lateral sclerosis): do not use until more is known
Maple syrup urine disease: do not use
Chronic alcohol use: linked with liver disease
Surgery: stop at least 2 weeks before, as they may affect blood sugar control
Reported side effects are fatigue and loss of coordination, so take care with driving