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Recent research has found that individuals who eat L-Leucine rich protein foods and exercise have more lean muscle tissue, a higher metabolic rate and naturally burn more body fat.
So what exactly is L-Leucine?
L-Leucine (aka Leucine) is one of three essential branched-chain amino acids (BCAAs) – the other two are L-Valine and L-Isoleucine. Leucine has long been used in conjunction with other BCAA’s as a supplement to help preserve muscle and improve recovery whilst losing fat. However, Leucine has recently emerged to be the most potent and beneficial of all of the Branched Chain Amino Acids after the release of recent research studies between 2006 and 2009 (see footnotes below).
Leucine = The Champion BCAA
What has been determined from the research is that Leucine on its own is one of the most anabolic amino acids a person can ingest. Studies have shown that it can:
- Help to preserve lean muscle tissue
- Preserve muscle glycogen
- Improve performance
- Supply the body with energy during bouts of extreme exertion
- Increase fat loss
- When consumed alone, Leucine is now believed to be the only amino acid that can increase protein synthesis
- When combined with other proteins give a huge anabolic response
- It has also been shown to speed up the recovery process and therefore stimulate muscle growth and prevent muscle breakdown.
Martha Stipanuk, PhD from Cornell University states
“At this point, it seems clear that most of the effects of amino acids on protein synthesis are mediated by Leucine.”
A Little Science
BCCA’s are called "branched chain” because of their molecular carbon side chains which are different to other amino acids. The BCAA's make up one third of the amino acid composition of skeletal muscle, but cannot be made by the body, and are therefore only acquired through nutrition; hence they are also essential amino acids. They function differently to other amino acids in that they are not metabolised in the liver, but in the muscle and contribute to the anabolic effect: increasing muscle tissue. Leucine is the fourth most concentrated amino acid in skeletal muscle tissue and accounts for around eight percent of the total amino-acid count in your whole body. As one of the three BCAA's it is essential for health as it has both medical and athletic applications. In particular it plays a special role in muscle metabolism, by exerting an anti-catabolic and anabolic effect on protein metabolism. In fact, Leucine assimilation into skeletal muscle has long been used as an indicator of protein synthesis within the muscle cells and oxidation.
Because Leucine stimulates protein synthesis amazingly well, even the BBC have reported that Leucine supplementation can combat and prevent sarcopenia - age-associated muscle loss and other muscle wasting disorders – due to its anti catabolic effects.
So with a little scientific background let’s see how Leucine has worked in the real world of training for improved body composition, increased recovery and improving performance?
Increased Protein Synthesis
Two Universities in 2005; Maastricht (Netherlands) and Birmingham (UK) jointly researched to determine post exercise muscle protein synthesis and whole body protein balance following the combined ingestion of carbohydrate with or without protein and/or Leucine. The researchers found that taking carbohydrate with protein and (0.1g per kg of bodyweight) Leucine supplement stimulated muscle protein synthesis and optimised whole body protein balance compared with the intake of carbohydrate and protein only.
The authors concluded their work by stating:
“The present data indicates that the additional ingestion of free leucine in combination with protein and carbohydrate likely represents an effective strategy to increase muscle anabolism following resistance exercise,”
In 2008, research backed this up by showing that Leucine achieves this muscle synthesising effect by activating a receptor on muscle cells called mTORC1, which in turn stimulates the conversion of amino acids into protein and muscle tissue.
Another study done by the Washington University School of Medicine compared the muscle protein synthesis rate in young and elderly men and women. Before the supplementation, the elderly subjects presented a lower rate of muscle protein synthesis. Following a 2-week exercise regime and intravenous supplementation of Leucine, the rate of muscle protein synthesis had increased to a comparable rate in all subjects. In addition, the elderly subjects presented a marked decrease in whole body protein breakdown.
Post Workout Recovery
Another study looked at post-workout muscle recovery. The researchers discovered that supplementation with Leucine again stimulated muscle protein synthesis following exercise but it also helped to restore muscle glycogen levels.
Improved Performance
Researchers in 2006, studying canoeists who completed a 6-week training phase, using either capsulated Leucine (45mg per kg of bodyweight) or a placebo found that power output increased significantly more in the Leucine group as well as time to exhaustion rose from a starting time of 6.3mins up to 7.3 minutes. The placebo group experienced no increase in their power or their time to exhaustion. The researchers speculated that this was likely due to lack of muscle damage with training and/or an increase in muscle protein anabolism.
Fat Loss
Finally Leucine has been shown even on low doses to increase fat loss, stabilise blood glucose levels and improve body composition due to its anabolic and catabolic properties, especially when on a calorie restricted diet.
Dr Donald Layman, the foremost authority on Leucine and BCCA’s stated:
"In studying exercise and how muscle develops, we found that leucine has a particularly unique effect in that it spares muscle proteins during weight loss, so you only lose the fat and not the muscle."
Therefore the benefits of Leucine are staggering and are still being researched to understand the full extent of them. However as more good news keeps rolling in about the potentials of such a powerful amino, one thing is for sure, it won’t be long before everyone knows about it.
Anyhow athletes and anybody wanting to increase muscle growth, preserve lean tissue, increase fat loss, improve on performance and recovery and generally be all round healthy should keep their eyes focused on Leucine nutrient dense diet and maybe look to supplement if necessary.
Why is Leucine So Anabolic?
Leucine seems to be an activating nutrient, in that for your body to make use of the protein you consume, you need adequate amounts of Leucine. The body basically checks for Leucine, and if it is available, the body assumes it has the amino acids it needs to increase protein synthesis. However, if you don't have enough Leucine in your diet your body will not make use of the protein that you have consumed, regardless of how much protein you have eaten. So basically you can consume a meal high in protein such as (cooked legumes i.e. kidney beans, chick peas and lentils) but without Leucine available the protein will not be absorbed, as well as animal protein which is much higher in Leucine. The table below gives a good average of healthy rich Leucine foods versus non rich Leucine sources.
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FOOD (Per 100g)
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Leucine
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An Excellent Whey Protein
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10-11g
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Beef/Veal/Game/Duck Chicken/Pork/Lamb/Goose
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2.5-3g
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Fish/Turkey
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2-2.5g
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Swiss/Cheddar Cheese
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2-2.5g
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Lentils
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0.65g
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Kidney Beans
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0.4g
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Chick Peas
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0.35g
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How to take Leucine
Muscle cannot be built by Leucine or BCAA’s alone unless other amino acids are available in the body from a previous meal or supplement. However as Leucine is the amino acid responsible for the anabolic effects of a meal, just adding a few grams of Leucine to it will increase muscle protein synthesis and increases protein turnover. So it is always best used with a meal which has protein already in it, as the other amino acids in the protein help with maximising muscle protein synthesis and protein turnover. If it is taken with a meal empty of protein, it will still stimulate some protein synthesis but only for 15-30 minutes.
Dosage
Leucine is a safe supplement as it is amongst the most tolerated amino acids and therefore no side effects have been reported. Studies have been done with a dosage of 0.1g of Leucine per kg of body weight i.e. 8g for an 80 kg male added to a whey and carb shake. Therefore taking 1-5g with a meal would work well to top up any Leucine deficiency within the meal. However make sure within your post workout shake you have some carbs and a good whey protein to take your Leucine with, and don’t exceed more than 20g per day.
Timing
To get the most out Leucine supplements try to time your consumption to when your body would naturally be breaking down muscle tissue and moving away from protein synthesis. This would always be pre workout, post workout, before bed and in the morning. Also take it regularly when you are on a calorie restricted diet or burning more calories in order to lose fat. Remember though that if you take it with food, the protein synthesis would last around 4 hours, so only use it a maximum of 4 times a day.
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