Branched-Chain Amino Acids: What are BCAAs and Do They Grow and Repair Muscle?

BCAA_The benefits of BCAA header


  • Branched-chain amino acids (BCAAs) have been a staple supplement for bodybuilders and athletes since the 1980s. They’re rich in the three muscle-building amino acids — leucine, isoleucine, and valine — and can help your muscles grow and repair faster in some situations.
  • If you’re eating plenty of complete protein (like meat) in a pre- or post-workout meal, you’ll already have the BCAAs your muscles need to recover, and a BCAA supplement is redundant.
  • However, BCAAs are great for preserving muscle during a fast, or for speeding up muscle growth from fasted workouts. If you like intermittent fasting, BCAAs are a great addition.
  • BCAAs can also help preserve muscle on Bulletproof Protein Fasting days.
  • Always check your BCAAs for added sugar, as well as artificial sweeteners and flavorings. You want something sweetened with a natural low-glycemic sweetener like stevia or monk fruit, without artificial colors or flavors.


Branched-chain amino acids (BCAAs) have been a staple supplement of bodybuilders and athletes since the 1980s. BCAAs contain the three musketeers of muscle-building amino acids: leucine, isoleucine, and valine. Amino acids are the building blocks of proteins, and these three help your muscles repair faster and encourage recovery after a tough workout. Plenty of people swear by BCAAs — but are they really necessary?

In some cases, no. Odds are a lot of folks aren’t getting much benefit from BCAAs. But if you use them properly, BCAAs can be your best friend when it comes to gaining muscle and recovering like a pro. They’re especially good in conjunction with fasting — either intermittent fasting or protein fasting — and can be a great supplement for anti-inflammatory low-protein diets.

Let’s take a look at how you can use BCAAs to build more muscle and recover faster, as well as when you can skip the BCAAs.

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The benefits of BCAAs

BCAAs contain leucine, isoleucine, and valine, the three main amino acids that your body uses to repair muscle. After a tough workout, your muscles are torn up and in need of repair. They build back stronger and you put on muscle — as long as you have plenty of those three special amino acids.

There’s good evidence that BCAAs increase protein synthesis (muscle building) and speed up recovery after a workout[ref url=””][ref url=”″]. However, if you’re eating complete protein (meat, fish, whey, etc.) before or after a workout, you’ll already get plenty of BCAAs. In that case, taking more in supplemental form is probably unnecessary, unless you’re running a marathon or doing a crazy two-hour CrossFit workout.

So if you have a good pre- or post-workout meal with a complete protein, BCAAs aren’t particularly helpful. Everything your muscles need is already in that grass-fed steak or wild-caught salmon.

Learn more here about the best pre- and post-workout meals to fuel your sweat session

That said, BCAAs have several useful applications. Here are some situations where BCAAs can help you build or preserve muscle.

BCAAs and intermittent fasting

BCAAs and intermittent fasting are a match made in heaven, especially if you work out in a fasted state.

Fasted workouts are great for you. Working out during a fast can burn up to 20 percent more fat (yes, you read that right)[ref url=””][ref url=”″], and fasting can help you build more muscle, too (here’s a breakdown of why).

The risk with fasting is that if you do an intense workout and then don’t eat, your muscles won’t have the right amino acids to rebuild. This is where BCAAs are great. Take 5 grams of BCAAs right after your workout — they won’t break your fast, and they’ll give your muscles the exact building blocks they need for repair. You get the best of both fasted and fed workouts.

Learn more here about intermittent fasting with this handy beginners’ guide

BCAAs and protein fasting/low-protein diets

There are surprising benefits to occasionally skipping protein for a day. Passing on protein for 24 hours is a great way to decrease inflammation and kickstart fat loss, and eating a lower-protein diet in general (about 15-20% of your daily calories) decreases oxidative stress, which slows down aging.[ref url=”″]

But like with intermittent fasting, low-protein diets and protein fasting days put you at risk for breaking down muscle — and again, BCAAs can come to the rescue. Five grams of BCAAs, taken once in the morning and once at night, will keep your muscles well-fed while giving you the full benefits of foregoing protein.

If you haven’t tried protein fasting, it’s worth your time to give it a shot. It’s one of the most underused (and most powerful) biohacks for inflammation. Here’s a full Bulletproof Protein Fasting protocol to get you started. Don’t forget your BCAAs while doing it.

BCAAs for immune function

BCAAs are also essential fuel for your immune system. Immune cells use BCAAs as building blocks for immune-boosting proteins.[ref url=”″] That means if you’re sick, stressed, or recovering from something like a surgery, BCAAs can help you fight off illness. Supplementing with BCAAs also helps you get rid of infections or illnesses faster.[ref url=”″]  A good dose is 5-10 grams a day, taken with food or without.

How to choose a quality BCAA supplement

Bodybuilding supplements tend to be loaded with artificial colors and sweeteners. BCAAs are particularly prone to artificial sweetening because they’re incredibly bitter in their pure form. They also often have fillers to help them dissolve into water (they’re not water-soluble on their own).

When you’re choosing a BCAA supplement, check the label to make sure it’s sweetened with stevia, monk fruit, or another Bulletproof-approved sweetener. Stay away from the big three artificial sweeteners. These are sucralose, acesulfame potassium (ace-K), and aspartame. Pass on artificial colors and flavors as well.

Even if you’re an exercise pro, freshen up your exercise routine with these four workouts to build muscle, lose weight, and boost energy.






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