Branched-chain amino acids are one of the best-known bodybuilding supplements. Promoted by health gurus like Tim Ferriss and Dave Asprey, as well as bodybuilding sites like T-Nation and Bodybuilding.com, branched-chain amino acids have become known as the must-have exercise supplement.
The thing is, the science on BCAAs is shaky at best. Most studies show no benefit whatsoever, and many are performed under unrealistic conditions.
One of the more well-researched early articles advocating supplementation with branched-chain amino acids ends by saying, “it’s clear that BCAAs may improve performance and body composition in certain situations.”
Using the words clear and may in the same sentence is a great way to not say very much at all, especially when combined with the “in certain situations” caveat. That said, the author is correct, but the research has also come a long way in the 14 years since that article was written.
I’m going to take a few minutes to explain what BCAAs are, what they actually do, why they aren’t worth buying, and what you should invest in instead.
What Do BCAAs Do?
Branched-chain amino acids are a group of three amino acids–leucine, isoleucine, and valine. All are numbered among the nine essential amino acids, and leucine is both the most important and the most abundant: proteins generally consist of around 5-10% leucine by weight, with whey protein being 11% leucine.
Like it says in the name, BCAAs have a branched-chain structure, which means they can connect to a lot of other amino acids at once. That makes them crucial, structurally-speaking, for assembling proteins, and it’s why they’re so abundant.
Their importance for hypertrophy (muscle-building) stems from the fact that leucine in particular has been shown to stimulate the production of mTor, an enzyme which acts much like an “on switch” for muscle protein synthesis.
That much is not controversial. What is controversial, and not particularly well-supported, is the idea that supplementing with either leucine or a mix of branched-chain amino acids will stimulate muscle growth above and beyond what you would get from just consuming protein.
The Research On BCAA Supplementation
A few studies have indeed found some benefits of BCAAs. In one study, wrestlers who supplemented with BCAAs were better able to maintain muscle mass in a caloric deficit.
However, what isn’t mentioned in the abstract is that the wrestlers were only consuming 80 grams of protein per day. At an average bodyweight of 150 pounds, and given their high level of activity, they should have been consuming around twice as much protein.
Studies usually do find that BCAA ingestion improves muscle protein synthesis. However, like the wrestler study, these studies usually compare the consumption of BCAAs to the consumption of carbohydrates or nothing at all, or else use subjects who aren’t consuming enough protein to begin with.
Other studies have looked at biochemical markers of muscle synthesis, rather than the end result of muscle growth. One such study found that elderly individuals who consumed 6.7 grams of essential amino acids saw a greater increase in biomarkers of muscle protein synthesis if the blend contained a greater proportion of amino acids.
However, the study did not actually measure muscle growth–and in any case, even for the elderly, a meal should contain far more than 6.7 grams (more like 20-40 grams) of protein!
That same study also found no benefit in young people from consuming 3 vs 1.7 grams of leucine.
Some studies have found an increase in muscle anabolic signaling from BCAAs… but no increase in actual muscle growth, and not even an increase in anabolic signaling beyond 1.6 grams of leucine.
After all, signaling isn’t enough–you need to actually have the raw materials to build muscle. And those raw materials are… all of the amino acids, not just some of them. Leucine alone is not responsible for the anabolic effect of protein.
Studies have sometimes found a slight benefit from BCAAs on post-exercise recovery, but most find no benefit at all.
Several studies have even found that BCAA supplements decrease muscle protein synthesis, net muscle protein synthesis (that is, muscle protein synthesis minus muscle protein breakdown), or total muscular protein turnover. Even to a BCAA skeptic, it’s not clear why this would be.
What about fatigue? A 2019 meta-analysis found that BCAA supplementation had no significant effect on fatigue. It did have statistically significant effects on several chemical markers of fatigue, but the actual effect sizes were minuscule, and again, that didn’t translate to an actual reduction in fatigue.
Okay, But You Need Leucine, Right?
Of course you do. You need all three of the branched-chain amino acids, along with the other six essential amino acids. No one is saying you don’t.
The question is how much of them do you need, and do you need to supplement?
Remember that T-Nation article I referenced in the beginning of this article? The author, Dr. John Berardi, recommends 8-16 grams of leucine per day, albeit only 1-4 for muscle-building and the rest for other purposes.
Now, the research I’ve cited here actually suggests you need more than that for maximum muscular anabolism– around 1.5-3 grams a meal, or 5-10 grams a day. Still, that isn’t a lot. Since protein is usually 5-10% leucine (just leucine alone–that’s not even including the other two BCAAS), anyone who gets the government-recommended 50 grams of protein a day is only getting around 4 grams of leucine, and maybe 8 grams of total BCAAs, since isoleucine and valine combined are about as abundant as leucine.
So, you need more BCAAs. The thing is, you also need more total protein–a whole lot more than 50 grams a day.
Maximizing muscular hypertrophy requires a protein intake of at least 1.6 grams per kilogram of bodyweight per day, which equates to 120 grams of protein for a 165-pound person. That in turn equates to around 8-10 grams of leucine and twice that much in total BCAAs–and remember, that’s the minimum amount of protein the study recommends.
That’s very low by bodybuilding standards; most trainers recommend eating at least a gram of protein per pound of bodyweight per day. Ironically, most of the people recommending BCAA supplements do this too, thus negating any possible need for BCAAs.
Of course, that’s for people who are primarily concerned with maximizing muscle growth. What about people who just want to be active and healthy?
According to Precision Nutrition, they should eat 1.4 to 2 grams of protein per kilogram of bodyweight per day, both for satiety and muscle protein synthesis. Yes, that’s about the same as the other study recommended, although it’s a range rather than a minimum.
Guess who runs Precision Nutrition? Dr. John Berardi, the author of the T-Nation article about how BCAAs are clearly, maybe, sometimes, useful. His protein intake guideline has robust research support, and if you follow it–if you even come close– you’ll have no need for BCAA supplements, ever.
So who should take branched-chain amino acids? Elderly people who don’t consume enough protein, maybe. Especially if they’re also vegans. That’s it really.
Branched-chain amino acids are very important and essential… components of each and every protein source you consume. Branched-chain amino acid supplements on the other hand are the most overhyped supplement on the market today. Save your money.