Leucine, valine, and isoleucine are the three branched chain amino acids (BCAAs), so named because of their non-linear (branched) structure of carbons. They are essential amino acids, meaning they are not produced in the body and must be obtained via diet, and yet they make up 35-40% of the content of proteins found in human tissues. They are primarily broken down in the muscle as opposed to the liver, like most other amino acids. This means they enter the bloodstream fairly rapidly and are readily available for uptake by the muscles and other body tissues. BCAAs play an important role in protein metabolism. Leucine in particular has been shown to promote protein synthesis and inhibit protein breakdown. This is a very good thing if you are trying to build muscle or maintain lean body mass.
For the endurance athlete, BCAA supplementation may promote resistance to fatigue and increase fat oxidation during exercise. In other words, you can tap into your fat stores (of which you have plenty) to utilize as an energy source as opposed to glycogen, of which you have a limited amount stored. Furthermore, BCAAs may improve recovery from exercise and have been shown to conserve muscle mass under extreme conditions characterized by protein breakdown and muscle wasting. Think ultramarathons, century rides, and trekking. Other studies have indicated the potential role of BCAAs in reducing central fatigue in response to strenuous exercise.
For the strength athlete, BCAAs increase the amino acid pool when taken prior to exercise, thereby providing the working muscles with free amino acids while they are needed most. This will help maintain an anabolic (muscle-building) environment in the body. BCAA administration prior to and following exercise has also been shown to reduce the severity and duration of delayed onset muscle soreness (DOMS).
WHO SHOULD/SHOULDN’T TAKE BCAAs:
BCAAs have been researched extensively and appear to be well tolerated by healthy adults. Athletes and recreationally-active individuals may benefit from supplementation, as well as those on low-calorie diets who are at increased risk of lean tissue breakdown related to weight loss. People with Maple Syrup Urine Disease (a congenital disorder that impairs BCAA metabolism) should not take BCAAs.
The exact dosage and ratio of leucine:isoleucine:valine is still debated in the literature, but most agree on a range of 4-20g per day. A recent recommendation for safe upper limit of leucine intake was 0.53g/kg body weight. That is roughly 35g of leucine per day if you weigh 150 pounds. That’s a lot of leucine! BCAAs can be taken before, during, and after workouts to maintain amino acid levels in the bloodstream, promote protein synthesis, and prevent protein breakdown. They may also be taken between meals if you feel your diet is not providing adequate levels of BCAAs in the form of protein from meat, dairy, fish, eggs, etc. BCAA’s are frequently sold in powder form, which can be mixed into liquid, or in capsule form.
BCAAs are beneficial for individuals who exercise regularly, or for those who are at risk for lean tissue breakdown. Research has shown them to be safe and pose no threat to healthy adults in doses of 4-20 g per day.