BCAAs and Protein Metabolism
Amino acids are the building blocks of proteins and certain hormones and neurotransmitters. They also function in many other metabolic activities, are used for energy production, are involved in immune function, detoxification, and also function as antioxidants. They are potent agents.
For example, amino acids rapidly regulate protein synthesis and degradation. Increasing amino acids stimulates protein synthesis and inhibits protein degradation. Supplying energy by only eating carbohydrates and fats cannot prevent protein breakdown; only certain amino acids allow for nitrogen balance.1
BCAAs, and in particular leucine, have been shown to have anabolic effects on protein metabolism by increasing protein synthesis and decreasing protein breakdown.2
Essential BCAAs, especially leucine, are used as energy releasing fuels during exercise. Depending on the duration and intensity of exercise, amino acids can provide upto 10% of the total energy needed for sustained exercise.3
Studies have shown that muscle wasting can be diminished by using BCAAs. They are also said to improve nutrition in chronic liver disease and to spare muscle protein from degradation.4
Apart from acting as a protein supplement, amino acids also have effects on neurotransmitters, hormones, control of protein turnover, renal function, and maintenance of the gut.5 Thus, amino acids can do more by actually regulating protein synthesis by acting as anabolic agents affecting hormonal functions.
There is evidence that amino acids play a role in the reduction of fatigue and the overtraining syndrome in athletes during exercise.
Amino Acids and Athletic Performance
One study showed that amino acid supplementation reduces the effects of muscle damage during the initial high stress of over exertion, and this effect may explain the enhanced ability of athletes to maintain muscle strength.
Oral amino acids increase amino acid availability and protein synthesis by influencing several pathways. Amino acids are important metabolites and also function as molecules with insulin-like effects.
For example, supplementation with only 6g of essential amino acids has been shown to elevate protein synthesis. BCAAs have been shown to reduce the breakdown of proteins and leucine has been shown to elevate protein synthesis.
Effects of Branched-Chain Amino Acids: Isoleucine, Leucine, and Valine
BCAAs are important sources of nitrogen for the synthesis of amino acids, such as glutamine and alanine.
These three amino acids – isoleucine, leucine, and valine – are involved in the regulation of protein metabolism, weight loss, body composition, and may be useful to enhance physical performance, stamina, or recovery, and for inhibiting the loss of muscle tissue due to aging.
Several studies have indicated that leucine is a regulator of protein metabolism by decreasing protein degradation and increasing protein synthesis.
The effects of long-term BCAA intake on overall metabolism and respiratory capacity have also been studied. It was discovered that the physical fitness of BCAA-treated people improved, and that BCAAs seemed to promote protein synthesis in fat-free body mass.
Additionally, leucine has been shown to increase the release of energy keytones, and also show a glucose-sparing effect (an essential survival mechanism for the brain during times of starvation).
Leucine has been found to lower the degradation of muscle protein even in normal resting people and this may help repair and recovery and be of importance to athletes doing regular physical training.
Leucine and the other BCAAs are used as energy by muscle cells, and are a source of cellular energy in the form of ATP and Phosphocreatine. There is a significant activation of BCAA metabolism with prolonged exercise, and current studies indicate that this is more pronounced in endurance-trained athletes.
BCAAs administered before exercise affect the response of some anabolic hormones, mainly GH, insulin, and testosterone. Studies found that the uptake of BCAA in muscle fibres can limit amino acid oxidation and prevent testosterone muscle clearance (the reduction of blood flow to the liver and kidneys during exercise).
This is also supported by the direct anabolic effect of BCAA, mainly leucine, on muscle proteins. An anti-catabolic (the prevention of the breakdown of muscle mass) effect of BCAA use was also noticed.
In sum, the study showed that the body’s response to exercise was changed by using BCAAs and that the anabolic hormone testosterone was positively affected when BCAAs were substituted for whole-milk proteins. This demonstrates the advantages of BCAA supplementation over the use of whole-food proteins, and even whole-food protein supplements.
One of the BCAAs, leucine is the most important for athletes. Leucine affects various anabolic hormones and has anabolic and anticatabolic effects. It is also involved in nitrogen metabolism and ammonia removal.
A study found that taking leucine lowered the breakdown of proteins in muscle. Using large amounts of leucine does not negatively affect the rate of protein synthesis.
Another study demonstrated the effects of BCAAs on protein degradation in working muscles during exercise. It concluded that taking BCAAs lowered the rate of protein degradation during exercise and might improve physical performance and would probably help repair and recovery after intense exercise.
They may also alleviate some of the fatigue experienced from prolonged exercise. Athletes should find these results very important.
BCAAs and Muscle Growth
Studies have found that increasing the use of amino acids may increase muscle mass as well and whole-body protein synthesis in young healthy men. Therefore, supplementing with BCAAs will help maintain the amino acid levels in muscle fibers, and could increase the rate of protein synthesis beyond what’s achievable by food alone.
BCAA supplements may also be helpful in reducing protein catabolism (muscle breakdown).
During exercise, feeding your muscles with more BCAAs can help to maintain a more favorable testosterone to cortisol ratio. The should enhance the productivity of your training session in terms of its growth-stimulating capacity.
Additionally, leucine may help reduce the catabolism (breakdown) of muscle protein. Therefore, BCAAs can prove to be very beneficial in this regard.
Increasing muscle is the net difference between protein synthesis and degradation and results in muscle gain during growth and development.
Therefore, in order to achieve optimal gains in muscle mass, you should optimize protein synthesis and minimize muscle protein breakdown. The results of numerous studies have shown that using BCAAs can be very helpful in this regard.
Leucine and Body Composition
Most people want to look good and fit and that means having less body fat and more muscle mass. Athletes are mainly looking to maximize body composition in order to maximize performance.
While bodybuilding is the ultimate sport for maximizing muscle mass and minimizing body fat for athletes in all sports, including both the power and endurance events, carrying excess body fat is detrimental to performance and maximizing muscle mass per pound of body weight is a universal goal.
Increased protein intake together with exercise results in improvements in body composition, an increase in muscle mass, and a decrease in body fat.
Increasing protein intake results in increased satiety and subsequently decreased calorie intake. Together with calorie restriction with and without exercise, increasing protein intake has been shown to result in effective weight loss with a preservation of muscle mass, and more weight loss from losing body fat.
Increasing protein also helps to keep the weight off and decreasing carbohydrate intake seems to increase weight and fat loss and improves body composition.
The BCAAs, and especially leucine, even at low doses have favorable effects on weight, fat loss, and body composition. The positive effects of leucine on protein metabolism, increasing protein synthesis, and decreasing catabolism (muscle breakdown), have been known for over three decades.
A study evaluated the effects of constant leucine supplementation and protein intake on body composition. The results indicate that long-term, low-dose leucine supplementation increases fat loss and improves the capacity of muscle protein synthesis.
Ammonia is mainly formed from the metabolism of amino acids during exercise. A study concluded that BCAA supplementation results in significantly greater muscle ammonia production during exercise.
Also, BCAAs impose a substantial ammonia load on muscle. The elevated BCAA levels also suppress protein degradation that normally occurs during intense exercise and duration.
Supplementation with BCAAs spares lean body mass during weight loss, promotes wound healing, may decrease muscle wasting with aging, and may have beneficial effects in renal and liver disease.
BCAAs are extensively used among athletes looking to improve their performance and muscle mass. Leucine stimulates and has a direct regulatory effect on protein synthesis.
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3. Amino acid and protein metabolism during exercise and recovery.
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4. Leucine. A possible regulator of protein turnover in muscle.
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5. Role of new nitrogen substrates during peri-operative artificial nutrition in adults.
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