Leucine must be acquired through food or dietary supplements and cannot be made by the body. This is why it is considered an essential amino acid. Leucine is also classified as a "branched-chain amino acid" (BCAA).
L-Leucine is the MVP of muscle protein synthesis and in anabolic muscle tissue reactions. This makes leucine the most important amino acid for athletes.
According to the Columbia Electronic Encyclopedia, 6th Edition, young adults require about 14 mg of leucine per pound of body weight. That would be about 2520 mg for a 180 pound person.
While leucine in its free-form version is great it is not required as whey protein can provide the proper amounts at a more cost effective way. In addition, at least one study says that whey protein provides leucine distribution at a slower rate than its free form counterpart offering a longer time period of muscle building.
There are several leucine metabolites that have exhibited extraordinary muscle building benefits that you can potentially benefit from.
Beta-hydroxy beta-methylbutyrate (HMB)
Alpha-Hydroxy-isocaproic acid (HICA)
Don't take my word for it. Here are a micro-sampling of the information available on leucine.
From Leucine triggers muscle growth by Jeff S. Volek, Ph.D., R.D. on nutritionexpress.com
Researchers at the University of Illinois conducted studies that examined weight loss diets containing 10 grams of leucine per day and 125 grams total of protein per day with a minimum of 2.5 grams of leucine at each meal. In two separate studies, the groups consuming high leucine diets had greater weight loss, greater fat loss and better preservation of lean body mass. In these studies, the high leucine diets also resulted in better glucose control.
From International Journal of Sports Physiology and Performance; 2011, Vol. 6, No. 1, 38-50
After 12 weeks, the placebo group had increased its maximum five-repetition weight resistance ability by 31 percent while the leucine group increased its ability by 41 percent.
The leucine group took 8 grams of leucine per day.
From Am J Clin Nutr. 94:809-818.
A team of researchers from the United States Army Research Institute of Environmental Medicine, Tufts University and the Louisiana State University System gave eight volunteers 10 grams of a protein drink containing either 1.87 grams or 3.5 grams of leucine during a cycling test. Those who got the drink enriched with 3.5 grams of leucine had a 33 percent increase in muscle synthesis over what the subjects who got 1.87 grams of leucine experienced.
From Ironman Magazine Leucine anabolic key to unlocking gains for older athletes.
The word anabolism is synonymous with growth. Clearly, essential amino acids are anabolic, but scientists have found that after the age of 50 people become resistant to their effects. Dr. Katsanos and his fellow scientists found that seven grams of essential amino acids stimulated protein synthesis in young people but completely failed to do so in older people. Does that mean that older people have lost the capacity to respond to amino acids? If so, then the muscle loss and the blunted response we see to resistance training are an inevitable consequence of aging. Fortunately, that is not the case. Senior trainees simply need a higher dose of critical elements in an essential-amino mixture.
Leucine appears to be the main essential amino acid responsible for protein synthesis.11 It’s the only amino acid that can stimulate protein synthesis alone.12 Because older people are resistant to the anabolic effects of amino acids, researchers investigated what would happen if they bumped up the leucine content from the original 1.7 grams to 2.8 grams in a seven-gram mixture.13 They found that the older people could stimulate protein synthesis to the same extent as young people. Research also shows that there are no differences in the building of muscle tissue between younger and older people at a dose of 15 grams of essential aminos.10
That implies that masters athletes can respond the way young athletes do, given a higher dose of amino acids.
From Leucine: Build Muscle With This Anabolic Amino Acid by Layne Norton on bodybuilding.com
Leucine activates a major complex in the anabolic (muscle-building) pathway called mTOR 5-7.
For those who are dieting but want to maintain maximum muscle mass, a leucine supplement may help alleviate some of the catabolic effects of a calorie-deficit diet. Leucine is more anabolic than other amino acids. While this hasn't been studied in detail, it might be possible to substitute something like 5g of leucine for 30-40g of dietary protein and still have the same or greater stimulatory effect on muscle protein synthesis.
Leucine has a far greater stimulatory effect on protein synthesis than any other amino acid. Protein synthesis increases similarly in response to a relatively small dose of leucine compared to a whole food meal. Also, adding leucine to a protein-rich meal further increases the rate of skeletal muscle protein synthesis.
From Unleash the Full Anabolic Potential of Food on T-nation.com
Just adding a few grams of Leucine to a meal, high protein or not-so-high protein, increases muscle protein synthesis by 50-70 percent in humans (3)(4) and increases protein turnover by over 500 percent!(5)
Apparently, orally administered Leucine stimulates muscle-protein synthesis by itself, independent of the insulin surge you get from a meal. However, it does seem that the role of insulin is permissive in that some rise in insulin is necessary to allow Leucine to do its work. (6)
The message is that Leucine is best used with a meal, rather than taken in-between meals by itself.
Additionally, adding Leucine to a 100% carbohydrate meal isn't the best idea, either. It seems the effects of Leucine are rate-limited if other amino acids aren't present.(6) That means that Leucine, while anabolic all on its own, won't do its best work unless there are at least some other amino acids present.
In short, a protein meal is good, but adding Leucine to it makes it much, much better.
Furthermore, it seems the change in Leucine concentration in the blood may be more important than the actual amount of Leucine in the blood, so you don't want to take Leucine non-stop.(1) It's better to take a scoop of it (about 5 grams) with a meal, let blood levels drop, and then take another scoop about 4 hours later.
I could keep going but you probably aren't as nerdy as me and want to get back to the gym.
The take away is focus on getting 2.5 to 5 grams of leucine with breakfast, pre-workout and post-workout meals. If you are under 40 years of age shoot for 7.5 grams per day and over 40 shoot for 15 grams per day.
Leucine is King (Part 1) For Muscle Building and ... - WHEY2MUSCLE
Leucine is King. Part 2 This is the Whey. - WHEY2MUSCLE - Blogger
Leucine is King: (Part 3) How Do You Get the ... - WHEY2MUSCLE
Leucine is King (Part 4): Headlines from ergo-log ... - WHEY2MUSCLE
Leucine is King (Part 5): Leucine metabolites - WHEY2MUSCLE
Leucine is King (Part 6) - WHEY2MUSCLE - Blogger
Leucine is able to drastically increase protein synthesis by activating mTOR, a signaling molecule that stimulates muscle protein synthesis
— SuppWithThat.com (@SuppWithThatcom) July 30, 2014
Why is whey protein so appropriate to ↗ post-ex muscle synthesis? (EAA: Essential Amino Acids) http://t.co/8FWR5iEAKM pic.twitter.com/ykMtN8yQTN
— Yann Le Meur (@YLMSportScience) March 10, 2015
7.12 g leucine daily stops muscle loss in elderly 06.06.2016
Leucine stimulates muscle growth without training 17.11.2015
Leucine: a myostatin inhibitor available from your supplements supplier 01.12.2014
Vitamin D3 boosts anabolic effect of leucine19.09.2013
Leucine supplement helps casein build muscles 14.09.2013
Maybe it's possible to stack leucine with HMB24.08.2013
Resveratrol-leucine combo boosts fat burning13.03.2013
Added leucine makes wheat protein as anabolic as whey 29.12.2012
Twelve grams a day of leucine boosts muscle mass 01.04.2012
Not so young any more? Leucine still works – with extra antioxidants 29.01.2012
Amino acid mix with added leucine makes muscles grow faster 10.10.2011
Leucine makes rowers faster 16.02.2011
Leucine supplement boosts fat burning07.02.2011
Most effective leucine dose may be as high as 20 g 05.10.2010
Leucine retains muscle mass when you're not training 30.08.2010
Leucine increases anabolic effect of post-training meal by 16 percent 16.08.2010