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L-isoleucine

What is L-isoleucine?

L-isoleucine is an essential amino acid that cannot be produced by the body and is known for its ability to promote endurance and support muscle repair and rebuilding. This amino acid is important for bodybuilders as it helps to boost energy and helps the body recover after exercise. There are 8 essential amino acids in total, which include L-leucine, L-lysine, L-methionine, L-phenylalaline, L-threonine, L-tryptophan and L-valine, in addition to L-isoleucine. (In addition to these 8 essential amino acids, L-histidine and L-arginine are often added to EAA supplements (1)). L-isoleucine is also classified as a branched-chain amino acid (BCAA). There are three branched-chain amino acids in total, which include L-isoleucine, L-valine and L-leucine. All three BCAAs help to promote muscle recovery after training. Within the muscle tissue, L-isoleucine can also be used to supply energy.

What does L-isoleucine do?

Like valine,isoleucine is a branched-chain amino acid and both serve as precursors for glutamine and alanine. Isoleucine is used by the muscle cells as an energy source, sparing other amino acids from being burned for energy. Like the other BCAAs, isoleucine also plays an important role in protein synthesis, anabolism and anti-catabolism. Without adequate amounts of BCAAs, muscle cells would not heal and grow. BCAAs can be supplied either in the form of a BCAA supplement or in the form of whey protein, which is rich in BCAAs (2).

The ideal ratio of L-isoleucine to the other BCAAs

Isoleucine should always be taken together with the other two branched-chain amino acids leucine and valine. Some believe that to ensure optimal absorption, you need two parts L-leucine and two parts L-valine for every part L-isoleucine. Others believe that a 1:1.8:1.2 ratio, which corresponds to the natural ratio of these amino acids in the muscles, is more effective. Some supplements even have a 4:1:1 or a 3:1:1 ratio. Which of these ratios is the best choice has not yet been conclusively determined.

Who needs L-isoleucine?

As L-isoleucine is an essential amino acid, everyone needs this amino acid for health reasons. People who train a lot or eat a low-protein diet should consider supplementing with BCAAs, which include L-isoleucine. BCAAs are essential for muscle protein synthesis and reducing protein catabolism. When BCAAs are taken in a ratio of two parts leucine, two parts valine and one part isoleucine, this increases muscle anabolism and consequently muscle growth. If you take too little of the branched-chain amino acids, you will unnecessarily limit your bodybuilding success.

References

  1. Essentials of Sports Nutrition and Supplements, p. 486
  2. Sports Supplement Review, p. 170