BCAAs: SUBSTRACTION BY ADDITION

Branched Chain Amino Acids (BCAAs) are one of the most, if the not the most, popular supplement in the resistance training world. For example, a well-known brand of BCAAs sells over 30 million dollars worth of their BCAA product a month on Amazon alone! That’s one brand on a single website!

What is ironic is that BCAAs are now being shown to have no positive impact on muscle protein synthesis; unless your diet is severely deficient in protein (which is likely not the case if you are a serious lifter).

In fact, while BCAAs decrease protein breakdown (which could be a good thing) they also reduce protein synthesis (which is a bad thing). (Wolfe, R.R. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?. J Int Soc Sports Nutr 14, 30 (2017)

The point is that BCAAs, despite their vast popularity and claims that they can help you build more muscle and recover faster from your training, are pretty much worthless unless you are severely deficient in protein.

However, here’s where it gets weird… or rather, interesting.

Leucine, which is one of the three BCAAs (the others being isoleucine and valine), if added to protein on it’s own makes that protein + leucine drink more anabolic! Meaning that it increases muscle protein synthesis and mTOR phosphorylation (which essentially activates the muscle-building process) more than the same amount of protein alone.

In fact, to get the same elevation in protein synthesis as the protein + leucine combo, you have to consume 4 times more protein!

But even more interesting is that when the researchers compared the protein + leucine group to a group receiving protein + the three BCAAs, the later group (leucine, valine, isoleucine + protein group) had less protein synthesis and mTOR phosphorylation than the protein + leucine alone group AND the protein alone group! (Tyler A Churchward-Venne et al, Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: a double-blind, randomized trial)

The reason for this is that isoleucine and valine compete with leucine for transport. The more isoleucine and valine you have, the less leucine you can absorb and the smaller effect it has. In fact, leucine, isoleucine and valine compete for absorption (Szmelcman S, Guggenheim K. Interference between leucine, isoleucine and valine during intestinal absorption. Biochem J 1966;100:7–11), transport and signaling (Hyde R, Taylor PM, Hundal HS. Amino acid transporters: roles in amino acid sensing and signalling in animal cells. Biochem J 2003;373:1–18).

Now, if leucine was equally as worthless as BCAAs that would not be an issue: reducing the efficacy of something with no benefits doesn’t matter.

However, the thing is that leucine by itself DOES have benefits when it comes to increasing muscle protein synthesis and growth.

For example, a recent study has shown that the consumption of leucine pre-exercise by athletes increased muscle protein synthesis and mTOR phosphorylation (trigger for muscle growth). Heck, it even increased time to exhaustion (the athletes were able to train for longer). (Wen, J., Fan, C., Liu, M. et al. Leucine‑enriched essential amino acids promote muscle protein synthesis and ameliorate exercise-induced exhaustion in prolonged endurance exercise in rats. Nutrire 47, 7 (2022).)

This is in line with the study I mentioned earlier about leucine + protein increasing muscle protein synthesis more than protein by itself.

WHAT DOES THIS MEAN?

Well, the take home message is pretty simple; BCAAs are not worth the money when it comes to building more muscle. BUT adding leucine by itself to a pre-workout drink will increase the efficacy of your workout by increasing mTOR activation and muscle protein synthesis, leading to more growth stimulation.

You can even ingest 3-5g of leucine about 10-15 minutes prior to your meals to make them “more anabolic”.

If you consume the two other BCAAs (valine, isoleucine) they will make the leucine lose its effectiveness by reducing its absorption as well as by competing for transport.

EAA (essential amino acids) supplements are not any better as you still have valine and isoleucine present competing with leucine. And it’s really the leucine that is the star player. Anything that competes with leucine and makes it less effective represents a waste of money.

Do NOT waste your money on EAA and BCAA products; they will not do anything to increase/speed up your gains, regardless of how popular they are.

However, using a pre-workout drink containing leucine, like Biotest’s Surge Workout Fuel, or adding 3-5g of leucine prior to your meals will definitely help you gain more muscle. Especially if it works synergistically with other ingredients proven to either increase protein synthesis or workout performance.