Walk into any gym in the world, and there’s a decent chance you’ll see someone toting around a gallon water jug filled with liquid the color of Nicki Minaj’s hair.
These are branched-chain amino acids (BCAAs), and they’ve been a staple supplement among gym-goers for decades.
Proponents believe they’re one of the best supplements for boosting muscle growth while bulking, preserving muscle mass and maintaining your energy levels while cutting, and can also improve immunity, recovery, and even improve weight loss.
Which all sounds great . . . except science proves they’re worthless.
As in . . . dryer-lint-mixed-with-chicken-boogers . . . worthless.
Keep reading to learn what BCAAs are, why people take them, and why you shouldn’t.
(Or if you’d prefer to skip all of the scientific mumbo jumbo and you just want to know if you should take BCAAs or a different supplement to reach your goals, no problem! Just take the Legion Supplement Finder Quiz, and in less than a minute, you’ll know exactly what supplements are right for you. Click here to check it out.)
Table of Contents
A protein is a large molecule made up of chains of smaller compounds known as amino acids.
Amino acids are the “building blocks” of many tissues in the body, including muscle, hair, nails, and skin.
Your body is able to make 11 of the amino acids it needs but must obtain the final 9 from the food you eat. These nine are called essential amino acids.
Branched-chain amino acids, or “BCAAs,” are a group of three essential amino acids called leucine, isoleucine, and valine that are chemically “chained” together.
While providing your body with an array of amino acids is important for building muscle, many people think BCAAs are particularly important because . . .
- Leucine directly stimulates protein synthesis, which means it plays a vital role in kick-starting the muscle-building process.
- Isoleucine improves glucose metabolism and increases glucose uptake in the muscles, which could help you train longer and harder.
- Valine doesn’t do much compared to leucine and isoleucine, though it may activate an enzyme responsible for cell growth known as the mammalian target of rapamycin, or “mTOR.”
You can get high amounts of BCAAs from quality protein sources such as meat, eggs, and dairy products (including whey protein), though some people also choose to use a BCAA supplement.
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Many supplement manufacturers sell two types of amino acid supplements: BCAAs and EAAs (essential amino acids).
The difference is that BCAAs only contain leucine, isoleucine, and valine, whereas EAAs contain all nine essential amino acids.
Supplement companies often claim that BCAA supplements boost muscle growth, promote weight loss, accelerate recovery, and reduce fatigue.
But when you examine the studies that appear to validate these claims, you realize that the arguments in favor of BCAAs are flawed.
One study that BCAA paladins regularly cite as “proof” that BCAAs help you improve your body composition was conducted by scientists at Weider Research Group. The researchers had participants follow a four-day strength training program for eight weeks and supplement with either BCAAs, whey protein, or a carbohydrate sports drink.
The results showed that participants who supplemented with BCAAs gained significantly more muscle and strength and lost at least twice as much fat as the participants who used the other supplements.
However . . .
- The results were never published in a journal and thus never underwent peer review.
- The BCAA supplement the participants consumed also contained glutamine and citrulline-malate, which makes it impossible to know how much the BCAAs contributed to the results.
- The researchers didn’t control the participants’ diets, so there’s no way to know whether the BCAA group made more progress because their diet was better than the other groups’.
In another study published in the Journal of the International Society of Sports Nutrition, a group of participants who supplemented with BCAA powder while dieting lost more fat, maintained more muscle, and gained more strength than a group of participants who supplemented with carbohydrate powder, despite both groups following identical training and diet regimens.
A team of shrewd scientists later discovered, however, that the study’s researchers had used questionable statistical analysis methods and made several errors in reporting their data, which makes these results hard to swallow.
Another sticking point for both of these studies is that they were funded by supplement companies whose primary product is a BCAA supplement. This isn’t “proof” of scientific misconduct, but it does mean we should be skeptical about their results until they’re verified by a disinterested third party (which hasn’t happened yet).
As the evidence for BCAAs muscle-building effects tottered, many BCAA hucksters changed their tune and began to emphasize BCAAs’ (supposed) ability to help you train longer and harder without becoming fatigued.
Research supporting this idea is thin at best, though.
For instance, one study conducted by scientists at the National Taiwan University of Sport showed that handball players who supplemented with BCAAs and arginine were less fatigued after playing in a multi-day competition than players who supplemented with a placebo.
Unfortunately, since the BCAAs were mixed with arginine, we can’t be sure that the BCAAs were responsible for the fatigue-reducing benefits—it’s equally likely that it was the arginine or the mix of the two (or their diets).
Given that a similar study on wrestlers failed to replicate these findings during a single-day competition, it’s also plausible that BCAAs only benefit athletes when they have to perform at a high level for more than one day.
Other research shows that BCAAs can increase the time it takes you to reach exhaustion during endurance exercise, but only when you don’t have enough glycogen (carbohydrates) stored in your muscles. When you aren’t “glycogen depleted,” BCAAs may make exercise feel easier, but they’re less effective than eating carbs in this regard.
TL;DR: You’re much better off just eating a banana than taking BCAAs if you want to perform better in your workouts.
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One of the most common reasons people use BCAAs is to hasten their recovery from exercise.
And while several studies show that BCAAs may be effective at decreasing muscle damage and improving recovery in some contexts, they all suffer from the same methodological issue: they only compare BCAAs to nothing, water, or carbohydrates—not protein.
In other words, they tell us that BCAAs are better at supporting recovery than consuming nothing, water, or carbs, but they don’t tell us that BCAAs do more for recovery than eating plenty of protein from whole foods.
Given that many whole foods have robust amino acid profiles that positively affect muscle recovery, you wouldn’t expect taking additional BCAAs from supplements to offer any further recovery benefits. And that’s exactly what science shows.
Fasted training is any exercise done while in a “fasted” state—the point when your body is finished processing and absorbing the nutrients in the food you’ve eaten, and insulin levels have dropped to a minimum (baseline) level.
The benefit of training fasted is it prevents insulin from hindering fat burning, thus accelerating fat loss. The main drawbacks are that it also increases muscle breakdown and tends to impair workout performance, and this is where some people believe BCAAs can help.
According to most supplement manufacturers, BCAA supplements don’t contain calories, so they won’t break your fast, but do contain leucine, so they’ll prevent you from losing muscle during your fasted training.
Sounds cool . . . but it’s simply not true.
How do supplement companies get away with claiming to the contrary?
Because a loophole in the FDA’s rules states that you can’t list the protein (and thus calorie) content of incomplete proteins. Since BCAAs contain only 3 of a possible 20 amino acids, they aren’t considered “complete.” In reality, BCAAs contain ~4 calories per gram—just like any other source of protein.
Some people also claim that you digest BCAAs so rapidly that they don’t interrupt your fast for long enough to be meaningful. Considering most people only do 30-to-60 minutes of fasted training at a time, though, taking BCAAs would still rob you of most of the supposed benefits of training fasted, even if they only raise insulin for a brief period.
If you consume a diet that contains plenty of protein and at least some carbohydrates, there are no advantages to supplementing with BCAAs.
Thus, the best alternative to taking a BCAA supplement is eating a high-protein and moderate-to-high-carbohydrate diet.
(And if you’d like specific advice about how many calories, how much of each macronutrient, and which foods you should eat to reach your health and fitness goals, take the Legion Diet Quiz.)
If you like to train fasted, you may want to supplement with β-Hydroxy β-Methylbutyrate (HMB)—a substance formed when your body metabolizes leucine.
While most scientists agree that HMB isn’t the potent muscle-builder that it was once believed to be, it does seem to be very effective at preventing muscle breakdown. It also has no effect whatsoever on insulin levels, which means it doesn’t break a fast.
This makes HMB perfect for use with fasted training. Its powerful anti-catabolic effects and non-existent effect on insulin means you reap all the fat loss benefits of training fasted without any of the problems relating to muscle loss or insulin secretion.
And if you want a 100% natural HMB supplement that also includes two other ingredients designed to help you get the most out of your fasted training, try Forge.
BCAAs are unlikely to cause any adverse side effects in most people.
That said, some research suggests BCAAs play a role in the advancement of diseases such as diabetes, nonalcoholic liver disease, cancer, maple syrup urine disease, and heart disease, though it remains unclear what role this is, and there’s no evidence they’re unsafe for otherwise healthy people.
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If you consume a high-protein diet, BCAA supplements are unnecessary. Therefore, there isn’t a “best BCAA supplement for men.”
No one needs to use a BCAA supplement if they eat a high-protein diet, including women. Therefore, there isn’t a “best BCAA supplement for women.”
Most supplement manufacturers claim that BCAAs help you build muscle, lose fat, recover faster, and feel less fatigued.
And while you can find evidence in the scientific literature to support these claims, the studies that do are plagued by methodological flaws.
If you already follow a high-protein and moderate-to-high-carb diet, BCAAs will do little to improve your body composition, athletic performance, or energy levels.
Emptying your wallet?
Jokes aside, provided you already eat a high-protein diet, there’s no reason to take BCAAs
Most people take BCAAs to aid muscle building, fat loss, performance, and recovery, but research shows they’re unlikely to deliver on any of these promises if you already consume a diet that’s rich in protein.
Unless you consume a diet that’s low in protein, no, BCAAs don’t “work.”
If you eat enough protein, no.
BCAAs are important for building muscle, but you can get them from your diet, so there’s no need to spend money on supplements.
If you consume a low-protein diet and feel like you’d benefit from taking a BCAA supplement, research shows the optimal dose of BCAAs is 200 mg per kilogram of body weight per day split into at least 2 doses.
For example, you could take 100 mg before and after your workouts each day. (Or you could just eat several portions of protein from whole foods throughout the day).
BCAAs contain ~4 calories per gram just like every other kind of protein, which is enough to elevate insulin levels and break your fast.
For most people, yes.
Some recent research has speculated that BCAAs might be involved in the advancement of some diseases, but the exact link isn’t well understood, and there’s no evidence they pose a danger to otherwise healthy people.
+ Scientific References
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