CrossFit, Leucine Supplements and protein synthesis.

What is leucine and what are amino acids?

Leucine is a branched chain amino acid (bcaa). Branched chain amino acids (bcaa) are amino acids that have a branched structure.  What are amino acids?  They are building blocks for protein.  Leucine is an essential amino acid.  So you need to get it from your diet

A lot of people in the CrossFit and Paleo communities are either strongly for leucine supplements, or strongly against them.   Researchers have identified it as a signal for muscle synthesis in animals.  There’s good a good chance it would do the same in people.   Leucine has been studied as a supplement for humans. A number of these studies have shown increased muscle synthesis and faster recovery in both older and younger men. Wasting in elderly men and women was halted with high-leucine whey supplementation.

What are amino acids: Leucine controversy  and  Insulin.

People who are against leucine supplements are probably concerned that leucine stimulates insulin production.  As discussed in an earlier post, insulin is not necessarily “bad.”  It serves very important functions, including stimulating protein synthesis.  And increasing movement of amino acids into muscle.  If leucine stimulates protein synthesis, it makes sense that it might do so by temporarily calling in insulin.  Research has shown that leucine actually improves blood sugar regulation.

Should you use a leucine supplement?

Possibly yes. There is a mechanism through which leucine can increase muscle protein synthesis. There are animal studies showing increased muscle synthesis with leucine intake. And there are limited human studies showing that leucine increases muscle synthesis in humans.

Good news for masters athletes is that younger and older people seem to show the same rate of response to leucine (Koopman et al. 2006).

Does increased intake show increased results? Most of the time “more” is not better.  (Selenium is a good example.)  Koopman et al. explored these questions and found that leucine did not increase muscle synthesis when protein intake was already sufficient (Koopman et al. 2008).  For more on protein intake see this article.

Current recommendations are to consume 20-25 grams of easily digested protein after resistance exercise.  It has recently been reported that the “window of opportunity” for protein intake following resistance training is open for about 24 hrs (Churchwood-Venne et al. 2012).  An intake of leucine and protein after resistance training increases muscle synthesis more than protein without leucine added.  Worst for muscle synthesis was carbohydrate alone (Koopman et al. 2004)

The main point for Leucine and amino acid supplements:

They might be helpful.  Few people enjoy uncertainty.  However, being falsely certain leaves too much to chance.  For more information take a look at this article on recovery and protein.

Anthony JC, Anthony TG, Kimball SR, Vary TC, & Jefferson LS (2000). Orally administered leucine stimulates protein synthesis in skeletal muscle of postabsorptive rats in association with increased eIF4F formation. The Journal of nutrition, 130 (2), 139-45 PMID: 10720160

Koopman R, Verdijk L, Manders RJ, Gijsen AP, Gorselink M, Pijpers E, Wagenmakers AJ, & van Loon LJ (2006). Co-ingestion of protein and leucine stimulates muscle protein synthesis rates to the same extent in young and elderly lean men. The American journal of clinical nutrition, 84 (3), 623-32 PMID: 16960178

Koopman R, Verdijk LB, Beelen M, Gorselink M, Kruseman AN, Wagenmakers AJ, Kuipers H, & van Loon LJ (2008). Co-ingestion of leucine with protein does not further augment post-exercise muscle protein synthesis rates in elderly men. The British journal of nutrition, 99 (3), 571-80 PMID: 17697406

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