The branched-chain amino acids include the three essential amino acids leucine, isoleucine and valine. They’re called branched-chain aminos because of their structure — each one has a forked outcropping that resembles a branch. In addition to being special for their structure, they are also special for numerous other reasons.
The main reason has to do with how the body handles them. When most amino acids are ingested, either as individual amino acids or as whole proteins, they are absorbed by the intestines and shuttled straight to the liver. There, the liver decides what to do with them before they go to the rest of the body. If the body needs more energy, the liver will break aminos down for fuel rather than spare them to repair and build muscle and other tissues. The three BCAAs, on the other hand, tend to be spared by the liver and get direct access to tissues like muscle fibers. Based on their needs, muscle fibers get to make the decision of what to do with the BCAAs. During a workout, muscle fibers can use them for fuel. After the workout is over, BCAAs can be used to build the muscle fibers up.
When it comes to building muscles, the BCAAs are the most critical amino acids — period. Of the three, leucine is the MVP because it is to muscle growth what a key is to a car ignition. In this case, the car is a muscle cell or fiber and leucine turns on the process of muscle protein synthesis, which builds up the muscle protein that leads to muscle growth. In more “sciencey” terms, leucine activates a complex called mTOR, which ramps up muscle protein synthesis and therefore muscle growth. Research suggests that gym-goers who added extra leucine to their postworkout protein and carb meal experienced significantly greater muscle protein synthesis than those just getting protein and carbs.
Another way that leucine acts as a potent anabolic agent is by spiking insulin levels. Like high-glycemic carbs, leucine increases the release of insulin from the pancreas, which helps to drive the amino into muscle cells where it can work to stimulate muscle growth. Insulin is also an anabolic hormone, encouraging muscle growth by promoting greater muscle protein synthesis and decreasing muscle protein breakdown.
Leucine also plays a role in fat loss. It can be somewhat confusing because insulin is known to increase fat storage and limit fat burning, but even though leucine spikes insulin, leucine and the BCAAs have been shown to actually encourage fat loss. One way may be because leucine acts as a potent hunger suppressor. Research from the University of Cincinnati shows that it also activates mTOR in the brain, essentially telling the brain that the body has ample energy, which leads to a drop in hunger and a boost in satiety and feelings of fullness. Another theory is that leucine has such a major impact on increasing protein synthesis throughout the body that the energy demand created for this process causes the body to burn more calories.
Valine for Energy
Numerous studies show that supplementing with BCAAs before exercise promotes muscle endurance and blunts fatigue. One reason is that the BCAAs are used directly by muscle fibers as an energy source. This is especially true during intense exercise like weight training.
Another way that the BCAAs keep you energized during workouts is thanks to valine. During exercise, the amino acid tryptophan (best-known as the culprit behind the post-Thanksgiving-dinner doldrums) is taken up by the brain in large amounts. Tryptophan is converted in the brain to 5-hydroxytryptamine or what you likely know as serotonin. Having higher serotonin levels during exercise signals the brain that the body is fatigued, resulting in a reduction in muscle strength and endurance. However, valine competes with tryptophan for entry into the brain and typically wins. If less tryptophan gets in, less gets converted to serotonin, and therefore muscles can contract with more force for a longer period before getting fatigued. And the benefits are not just gym-based. Valine can help you stay more alert and keep your brain sharper during the day when you are not working out.
While leucine plays the major role in promoting muscle growth and fat loss, and valine has become famed for its role in energy conservation, isoleucine has its own advantages. Most notably, it plays a role in fat burning, one that is unique from the way that leucine aids fat loss, making the benefits additive.
Japanese researchers discovered that mice given isoleucine while eating a high-fat diet gained significantly less fat than mice not getting supplemental isoleucine in their diet. This was a result of isoleucine’s ability to activate special receptors, known as PPAR, that increase fat burning and inhibit fat storage. PPAR works to increase the activity of genes that encourage greater fat burning in the body while decreasing activity of genes that increase fat storage.
BCAAs in Combo
While each of the three individual BCAAs has its own unique properties, taking them together is the best way to get all the advantages that they provide. Although research has pegged leucine as the most active when it comes to muscle growth, all three aminos are critical building blocks for muscle protein. Plus, the majority of the studies showing their benefits on muscle hypertrophy were done with BCAA supplements, not leucine on its own.
Scientists from Baylor University in Texas compared the effects of BCAAs against leucine. They gave men either just leucine, all three BCAAs or a placebo before workouts and immediately after workouts. They reported in a 2008 issue of the Journal of the International Society of Sports Nutrition that although leucine increased muscle protein synthesis after the workout significantly better than the placebo, the BCAA supplement increased muscle protein synthesis significantly better than the placebo and leucine alone.
BCAAs also have been shown to enhance immune function following exercise. Because intense exercise can take its toll on the immune system and increase the chances of getting sick, supplementing with BCAAs is a smart idea to keep from catching a cold or flu and missing time in the gym.
BCAAs also may help to increase life span. Italian researchers discovered that mice fed BCAAs had higher amounts of mitochondria in their muscles, higher activity of the longevity gene SIRT1 and lived 12 percent longer than those not getting BCAAs. Although these benefits have yet to be confirmed in humans, they are potential fringe benefits from a supplement that you are probably taking to reap greater muscle size and strength.
We recommend that you take about 5 grams of BCAAs with a morning protein shake, as well as your preworkout and postworkout protein shakes. And you may even want to consider adding 5 grams of BCAAs to your water bottle to sip on during workouts. Be sure you use a supplement that provides leucine in at least a 2:1:1 ratio to isoleucine and valine.