When eating less to reduce weight, it is hard not to lose some muscle mass. During dieting, the body struggles to produce sufficient energy for the basal metabolic rate and physical activity, and therefore, it may break down muscle proteins to satisfy the energy needs. While the basic equation for muscle mass is the rate of protein synthesis subtracting the rate of protein breakdown, the decrease in muscle size will be observed if muscle protein breakdown is not prevented while on a calorie-deficit diet.
It has been well established that branched-chain amino acids (BCAAs) not only stimulate protein synthesis but also reduce the rate of protein breakdown. BCAAs consist of three amino acids: leucine, isoleucine, and valine, which make up about one-third of skeletal muscle in the human body. They increase muscle protein synthesis by affecting the cellular components in the protein synthesis pathway and decrease the substances involved in muscle protein breakdown. BCAAs are important for maintaining and gaining muscle mass.
BCAAs are abundant in whey, a commonly-used workout supplement. However, further digestion is needed before the BCAAs in whey are released into the bloodstream. Therefore, pure BCAA supplements may be more efficient as the pre- and post-workout supplements, since they provide an immediate source of these amino acids to a greater and faster extent than whey.
During dieting, consuming foods rich in BCAAs may be an effective strategy to prevent muscle loss. As always, whole foods are recommended because they contain more nutrients and provide more benefits for health. BCAAs may be found in many natural foods. Chicken breast, lean ground beef, flank steak, turkey breast, wild salmon, tuna, tilapia and dry-roasted peanuts are high in BCAAs (5-7 gram BCAAs per 6 oz). Egg also contains a rich amount of BCAAs in its protein content. Among these foods, an egg has the most leucine content per gram of protein, which is the main driver of protein synthesis. Six ounces of the meats and fishes listed above contain enough BCAAs to maximize muscle protein synthesis. Although it takes six or more eggs to provide the effective amount of BCAAs, considering the rich content of vitamins, essential fatty acids, choline, and cholesterol that are essential for muscle gain and maintenance, the whole egg is still a great food for both trained and untrained individuals who want to gain muscle or prevent muscle loss during dieting.
By stimulating protein synthesis and diminishing protein breakdown, BCAAs provide many appropriate mechanisms for gaining muscle mass and preventing muscle loss. Besides whey and pure BCAA supplements, many common whole food sources, such as meats, fishes, and egg, contain a great amount of BCAAs. While supplements provide an immediate spike of these amino acids, whole foods are always recommended for more integrated nutrient content to maintaining good health. Therefore, when making meal plans, make sure to include these whole foods rich in BCAAs in your diet!
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2. Yoshiharu Shimomura, Taro Murakami, Naoya Nakai, Masaru Nagasaki, Robert A. Harris. (2004) Exercise Promotes BCAA Catabolism: Effects of BCAA Supplementation on Skeletal Muscle during Exercise. J. Nutr. 134: 1583S–1587S.
3. Kimball SR, Jefferson LS. (2004) Regulation of global and specific mRNA translation by oral administration of branched-chain amino acids. Biochem. Biophys. Res. Commun. 313:423–7.
This article was originally published in the Sydney & J.L. Huffines Institute for Sports Medicine & Human Performance website (2014)