Do BCCA's Make a Difference?

In the highly competitive world of athletics, the margin separating victory from defeat is often small. As a result, athletes know that the difference between medaling and placing off the podium can be a few hundredths of a second.

They know the difference between optimal performance and sub-optimal performance means optimizing all aspects of their sport. They also know that all else being equal, any little edge they can get over their competition will likely lead to more successful performances.

As a result, ergogenic aids have emerged as a vital component in the training regimens of athletes. An ergogenic aid is generally a substance or training device known to enhance athletic performance.

Of course, with over 30,000 nutritional supplements and natural food products competing in the marketplace today, many of which promise better body composition and performance, few promises of improved performance are realized. (Yep, you read that right – 30,000). It's no surprise that it's often difficult for athletes to sort out what works from what doesn't.

In this article, we'll discuss the effectiveness of one of these supposed ergogenic aids – branched chain amino acids (BCAA). While BCAA aren't new, there's a wave of new research looking at how this unique group of amino acids can impact body composition and performance. As a result of this literature, it's clear that BCAA may improve performance and body composition in certain situations.

This article will focus on three potential mechanisms of action by which BCAA can impact performance:

1. Enhanced muscle protein synthesis and muscle protein accretion in response to strength training and BCAA supplementation.

2. Improved body weight control and fat loss during energy restricted diets with adequate protein and BCAA.

3. Improved endurance performance via the prevention of central fatigue and/or other factors with BCAA supplementation.

ABOUT BCAA

The branched chain amino acids consist of three essential amino acids:

1. Leucine

2. Isoleucine

3. Valine

These hydrophobic (water-fearing) amino acids are referred to as "aliphatic" as their central carbon attaches to a branched non-cyclic, open carbon chain, as seen below with leucine.

It's been shown that BCAA can comprise up to one-third of muscle protein (Mero, 1999) and of the three BCAA, leucine is the most heavily researched. It's this amino acid that appears to offer the biggest physiological benefit.

Based on what we currently know, leucine has a higher oxidation rate in skeletal muscle due to its chemical structure, plays a significant role in protein synthesis, and is unique in its ability to participate in several metabolic processes. Specifically, researchers believe that the BCAA, especially leucine, may work through the following mechanisms:

1. Modulation of insulin signaling

2. Regulation of muscle protein translation initiation

3. Nitrogen donation for alanine and glutamine

4. Prevention of free tryptophan in plasma from entering the brain and central nervous system

LEUCINE AND RESISTANCE TRAINING

It's common knowledge among the scientific community that resistance training results in the hypertrophy of trained muscles, largely due to increased protein synthesis in relation to protein breakdown. Of course, studies have shown protein degradation also increases with strength training, and only with proper nutritional intake is a net gain in protein status – leading to increased muscle mass – observed (Blomstrand et al, 2006).

This alone highlights the vital role nutrition can play in muscle growth, as both carbohydrate and protein intake can be beneficial. Simply put, adequate protein intake and overall caloric intake are required to stimulate a positive protein balance in response to resistance training.

How these shifts in protein intake come about is a hotly debated topic. Some researchers believe that an increased availability of amino acids at the muscle directly stimulates protein synthesis. Others believe that muscle protein synthesis increases via a stimulatory effect of a single amino acid or group of amino acids such as the BCAAs (Blomstrand et al, 2006).

Others believe that certain amino acids (such as the BCAA) are capable of stimulating a variety of metabolic pathways, including the modulation of insulin release, and it's the anabolic potential of insulin – in the presence of amino acids – that triggers muscle growth. Of course, some researchers believe that all these are necessary to promote training-induced muscle growth.

LEUCINE AND THE MODULATION OF INSULIN RELEASE

As many know, the release of insulin has been correlated with many anabolic properties involved with tissue building. Insulin has been proven to stimulate protein synthesis and inhibit protein breakdown when administered both during and post-exercise (Manninen et al, 2006).

Interestingly, in an investigation by Manninen in 2006 involving the supplementation of a carbohydrate, protein hydrolysate, and leucine mixture taken during exercise, it was demonstrated that this mixture leads to greater increases in skeletal muscle hypertrophy and strength vs. a placebo supplement.

It was once believed that insulin secretion was controlled almost entirely by blood glucose concentration. It's since become apparent that amino acids play a crucial role in the regulation of insulin secretion. Certain amino acids have been shown to cause insulin release in humans, even under conditions where blood sugar levels are normal (Manninen et al, 2006).

Of course, in order for most amino acids to effectively stimulate pancreatic beta cell insulin release, permissive levels of blood glucose (2.5 – 5.0 mM) must be present. Interestingly, leucine is an exception, as it's the only amino acid capable of increasing circulating insulin levels regardless of blood glucose concentration (Manninen et al, 2006). The increase of insulin has been shown to decrease the rate of muscle protein degradation.

By limiting protein degradation, leucine may allow for a net protein synthesis post-resistance exercise, leading to greater muscle hypertrophy. Essentially, this insulin response will provide an environment that promotes tissue building, as opposed to tissue breakdown.