WILL LEUCINE POWDER INCREASE MUSCLE PROTEIN SYNTHESIS?

RESISTANCE EXERCISE LEUCINE AND MUSCLE PROTEIN SYNTHESIS

Resistance exercise muscles are exposed to tension. Some lifters will use an exercise bar with resistance bands to add further tension. Whether the tension is from manual resistance exercise with weights or body weight resistance exercise, the total resistance exercise should accumulate over weeks for muscle growth. Resistance exercise is the best protein synthesis powder!

Muscle growth occurs when muscle protein synthesis (MPS) exceeds muscle protein breakdown (MPB). Inadequate essential amino acids can cause muscle breakdown. To build muscle, protein balance must favor muscle anabolism. MPS and MPB are responsive to diet, specifically protein feeding and the subsequent elevation of amino acids and mechanical loading, including resistance exercise (1, 2).

ESSENTIAL AMINO ACID MIX POWDERS MAY BE BENEFICIAL FOR THOSE DIETING

Dieting can cause one to lose muscle due to skeletal muscle proteins being broken down and used as an energy source. Increasing protein synthesis requires an elevation of insulin levels and adequate leucine intake. Bodybuilders will often take either branched chain amino acids (i.e., BCAA supplements) or leucine supplementation to increase MPS.

Essential amino acids are required in the diet, which is why some amino acids are called essential. The best essential amino acid supplement should contain a full spectrum of amino acids.

The body can make nonessential amino acids. Incomplete proteins are missing at least one essential amino acid. There has been much controversy regarding branched chain amino acids vs. essential amino acids.

BCAAs do not contain the full spectrum of EAAs. When an essential amino acid is lacking in the diet/if diet is lacking an essential amino acid, this is not optimal for protein synthesis.

LEUCINE HYPOTHESIS

The “leucine hypothesis” suggests that the magnitude (amplitude and rate) of meal increase in blood leucine concentrations, termed leucinemia, serves to regulate the magnitude of post-meal MPS response to an ingested protein source(3, 4).

For example, whey protein results in a greater increase in muscle protein synthesis than soy protein and casein due to higher amounts of leucine in whey. Some lifters advocate leucine pre workouts powders combined with an essential amino acid supplement powder to stimulate MPS.

A lifter may conclude that adding some leucine powder to your meals and protein shakes can increase muscle protein synthesis and muscle growth. If you eat 20-30 grams of high-quality protein per meal, you should save money by adding leucine.

The maximum amount of leucine to stimulate MPS significantly above resting levels is approximately 2 grams for younger adults and 3 grams for older adults.

OLDER ADULTS MAY BENEFIT FROM A LEUCINE POWDER AND ESSENTIAL AMINO ACID MIX SUPPLEMENT

Older adults need more leucine due to anabolic resistance, in which they become desensitized to the anabolic actions of leucine and need a larger dose for optimal effects. However, some studies are showing above 3 grams stimulated muscle protein synthesis more(5, 6). Muscle protein synthesis is increased when a complete spectrum of essential amino acids is present compared to leucine alone. For example, low dosages of leucine combined with other essential amino acids result in greater protein synthesis than leucine alone.

Thus, protein synthesis is only partially dependent on leucine availability. Instead, an abundant supply of amino acids, including EAAs (and potentially nonessential amino acids) is also needed post-workout to provide additional substrate for the synthesis of new muscle proteins under conditions of higher “anabolic drive” stimulated by resistance exercise than feeding alone.