For the longest time I was never a big fan of branched chain amino acids (BCAAs).  I had always gotten my fill of protein and BCAAs through food and the thought of adding extra BCAAs seemed like a waste of money and a scam.  I had the holier-than-thou mindset and thought BCAAs were for the weak and easily scammed.

Well apparently now I am weak and easily scammed.  I’ll take that since I’m gaining muscle while fasting for 16 hours a day, even in the anabolic window. 

See: My Experience Anabolic Fasting

For those not in the hip gym talk, the anabolic window is the 30-90 minutes post exercise where you need to feed your muscles protein and carbs so they grown or else they breakdown and you lose all your gainz.  When you are trying to look better naked, missing the anabolic window is worse than losing your child, all your money and then getting kicked in the no-no zone repeatedly by a soccer payer all at the same time.  Yea it’s that bad.

Before I go any further, let’s take a step back and define what BCAAs are and where they come from.  Protein is made up of amino acids, both nonessential and essential.  Nonessential amino acids can be made in the body, so if you don’t directly ingest them you’re all set; the body will just make them on it’s own.  Essential cannot be made in the body.  These need to be ingested through your diet.  Three essential amino acids are the BCAAs.  By taking a BCAA supplement, you are just cutting out the middle man of digestion.

I might get a little deep in the weeds with the descriptions of the different BCAAs, so if your eyes start to glaze over, just remember the bolded text.  It’s the take home message and you’ll still be better educated than 95% of your friends and Bro-scientist.

The BCAA supplement you see in the store or online is mainly made up of Leucine, Valine and Isoleucine.  Sometimes there is glutamine and other stuff that you can do without mixed in for “added benefit”.

Here’s the breakdown…


If Leucine was a basketball player, it would be a hybrid of Bill Russell, Wilt Chamberlain, Michael Jordan and LeBron James.    The MVP of the BCAA world, Leucine is responsible for signaling protein synthesis aka gainz. 

After you workout and cause damage to your muscles, your body is in a catabolic phase.  The catabolic phase is the breakdown of larger molecules into smaller ones to help restore balance in the body.  Sometimes the larger molecules are fats and carbs, sometimes it’s protein from your muscle.  This is why when you are trying to lose weight, many people lose strength.  They are using their muscles as a fuel source.

To avoid this, the body needs a signal to go into an anabolic phase.  In the anabolic phase protein synthesis is stimulated and muscle is built.

The way I remember this is anabolic steroids build muscle and catabolic is cannibalism.

Leucine stimulates mammalian target of rapamycin or mTOR (don’t worry there will be a quiz later).  mTOR does a lot of things in the body but for us, it is the light switch that turns on the protein synthesis.

Besides being the boss that turns the anabolic light switch on, Leucine also contributes to regulation of blood-sugar levels; growth and repair of bone tissue; growth hormone production; and wound healing.  Like I said, the MVP of the BCAA world.

So why not just take Leucine and be done with it?  Because all 3 BCAAs (Leucine, Valine and Isoleucine) have been shown to increase protein synthesis more than Leucine alone1.  The difference in price between just Leucine and a BCAA supplement is like $10.  Don’t trip over hundreds to save pennies.

As far as dosages go, the minimum effective dose to stimulate protein synthesis is 3g.  Between 3-5g is safe to take and the chance of side effects is low. 

Since you asked, supplementing with 15g or more has been shown to cause upset stomach, nausea, diarrhea and vomiting. Not my idea of a fun day.

In one study, healthy men took 500-1250 mg/kg of Leucine (45.4 – 114 g for 200lb guy) which caused an increase in ammonia in the body.   Therefore, the upper limit was then set at 500mg/kg.


Of the 3 BCAAs, Valine is the red headed step child.  Studies isolating Valine are not as common as Leucine and Isoleucine, so there is little known about it.

What we do know is Valine can be converted to glucose in the liver and the the energy source of the BCAA group as well as stimulating protein synthesis (less effective at this then Leucine).

What I found particularly interesting, Valine and tryptophan compete for the same receptors in the brain.  Yes, the same tryptophan that makes you sleepy on Thanksgiving makes you tired after a workout.  When you exercise, tryptophan is released in large amounts.  Tryptophan is then converted to serotonin in the brain.  Serotonin regulates signal intensity.  Serotonin is the volume on your TV.  Higher the volume = more signal.  High levels of serotonin can lead to the fatigued feeling.  So by taking Valine, you can lower then tryptophan that is converted to serotonin and increase the amount you can workout before you throw in the towel.

There hasn’t been an effective dosage found yet for Valine.  Like I said the red headed stepchild.

Aim for 1g of Valine in your BCAAs.  Any less than this can work against you in slowing down tryptophan.


Isoleucine promotes glucose uptake and consumption.  Basically, it helps transport glucose to to the cells for use rather than storage (stored glucose turns to fat).  It can also be converted to glucose if needed.

Isoleucine along with Valine are used for energy by the muscle cells which spare the muscle themselves.  Ideal if you are training in a fasted state.   Since it can be used for energy, Isoleucine increases muscle endurance.

It has also been shown to aide in fat loss.  A study has shown that mice fed a high fat diet and an Isoleucine supplement stored less fat than mice not given the supplement.  This was because Isoleucine signaling special receptors, peroxisome proliferator-activated receptors (PPARs), which increase fat burning and hinder storage2.

For a dosage, about 0.019g/kg (1.7g for a 200lb person) is recommended. 


BCAAs have their place in a workout cycle.  If you’re bulking or maintenance phase, the protein from your diet should more than cover your BCAA requirements.  In this case I would skip them as they are like adding gas directly to your engine when you already have a full tank of gas.

However, if your fasting or in a cutting phase, then I would suggest the addition of a BCAA supplement to prevent muscle lost or in some cases muscle gain. 

The 3 things to look out for in a BCAA supplement are (in decreasing level of importance):

  • 3-5 grams per serving of Leucine
  • At least 1g of Valine and Isoleucine per serving
  • Flavor (I got blue raspberry once. I’d rather lick the bottom of my shoe than make that mistake again)

The anabolic effect of BCAAs has been shown to be beneficial prior to the workout compared to other times3.  However, if your training in a fasted state or cutting, I recommend pre and post workout BCAA supplementation.

Reputable Brands

The ratio you see on the containers is Leucine: Valine: Isoleucine. Stay away from BCAAs that have 10:1:1 ratios or anything ridiculous like that.  There is less Valine and Isoleucine in those than you need.  Stick to a 2:1:1 ratio or something close and look for at least 5g of BCAAs (3g Leucine, 1g of Valine and Isoleucine each).

I am a huge fan of MusclePharm.  Their BCAA supplement, Amino 1,  hits all the recommended dosages and the flavoring is just right.

I’ve tried XTend by Scivation and got good results with that.  Do you remember as a kid making Kool aide with too much sugar?  Like enough sugar that you had to chew it before you swallowed it?  XTend is about that sweet.  If you dilute it to a full gallon container it might not be bad but for anything under 20 oz. of water it makes it hard to drink without going into a fake sugar diabetic shock.  Sweetness aside, it’s a very good product and hits a good amount and ratio of BCAAs.

Sometimes labels list BCAA amounts in mg instead of g.  So you might see 3450 mg of Leucine, to convert to g just divide 3450 by 1000.  So in our case, this supplement would have 3.45 g of Leucine.

Disclosure: To be transparent, I am an affiliate of  So if you purchase something through the links above, I get a cut with no extra cost to you.  This helps keep my lights on, so I and my wife thank you.  The products I put up are not to make a quick buck on my end, I used and vetted all these products to give you the highest quality.  If I recommended products I didn’t use I would lose the trust of my readers and then I’d be left alone and in the dark.

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  1. La Bounty, P., et al., The effects of oral BCAAs and leucine supplementation combined with an acute lower-body resistance exercise on mTOR and 4E-BP1 activation in humans: preliminary findings. Journal of the International Society of Sports Nutrition, 5(Suppl 1):P21, 2008.
  2. Nishimura, J., et al. “Isoleucine Prevents the Accumulation of Tissue Triglycerides and Upregulates the Expression of PPAR{alpha} and Uncoupling Protein in Diet-Induced Obese Mice.” J. Nutr., March 2010, in press
  3. Tipton KD, et al Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise . Am J Physiol Endocrinol Metab. (2001)