The Anabolic Power of Leucine. By Veeraj Goyaram

By Veeraj Goyaram

Cape Town, South Africa. March 27, 2015 

If you read my article that I published on this website in 2013 you will definitely find out that I am big fan of the amino acid Leucine and that I recommended taking Leucine in between protein meals in order to keep the "anabolic switch" on. I am pleased today to devote an article entirely to Leucine in order to teach you some of the important things you need to know. Sorry, I will have to bore you with graphs and metabolic pathways. However, these are simply to show you real published scientific data and that I am not cooking up any values. 

1. Quick Revision:

As you know, Leucine is one of the three Branched Chain Amino Acids (BCAAs) and is the most significant among the three, and even among all other amino acids, in terms of boosting muscle growth. Leucine can stimulate protein synthesis in skeletal muscle by activating a special protein called mTOR. My professor at the university nicknamed me mTOR because of my obsession with this protein. mTOR is known as a signalling protein, meaning that it serves to transmit signals in the muscle cell, signals that increases PROTEIN SYNTHESIS in skeletal muscle. 

Leucine can directly activate the anabolic switch mTOR, an ability that it shares with the powerful anabolic hormone Insulin and IGF-1

2. The Anabolic Power of a Protein Depends on its Leucine Content

That's true. The higher the Leucine content of a protein source (up to a certain point) the greater is its anabolic power. In a study by Dr. Layne Norton and his colleagues (Norton et al., 2012) from the University of Illinois at Urbana-Champaign it was found that protein with a higher leucine content, namely egg and whey protein, were found to be more anabolic than proteins like Wheat and Soy when fed to rats. Wheat protein contains 6.8%, soy has 8% while egg and whey have 8.8% and 10.9% respectively of Leucine. 

Figure 1:
FSR is a measure of protein synthesis in muscle.
(Source: Norton et al., 2012)

 The practical applications of this finding is that if you are vegan then you need to

(a) Up your protein intake per meal so that you achieve a certain critical Leucine intake (a.k.a. "Leucine threshold") which is able to stimulate protein synthesis. This threshold is about 3.2-4.4g of Leucine which means that you should aim to ingest this amount of Leucine each time you eat a meal and drink a shake. As you can see, there is a range for this Leucine threshold (3.2-4.4g) and a lighter individual would need to consume Leucine in the lower end of this range. The converse is true for the larger individual. Well, there's no need to walk with a scale and calculator to measure things to the milligram. Aim for a decent 3.5g Leucine per intake. You may wish to take a little more for good measure but there's no need to go overboard like consuming 10g Leucine per meal (see section below)

(b) Boost your protein meals with extra Leucine because research (Norton et al., 2012) has shown that adding Leucine to Wheat protein can boost its anabolic properties and bring it to the same level as whey protein. What you can do if you are a vegetarian eating a vegetable protein meal is to drink a small whey shake along with the meal. If you are vegan and thus cannot consume whey then you may use a BCAA supplement of vegan origin. I am not vegan but I am currently using a vegan BCAA supplement called iBCAA™ made by a trusted manufacturer called Innobio. 

Figure 2:
MPS stands for Muscle Protein Synthesis.
WGG=Wheat Protein, WGL=Whey Protein + Leucine
Source: Norton et al., 2012 

3. Beyond the Leucine Threshold you may simply be wasting your money

Research has shown that eating more than the leucine threshold (3.2-4.4g Leucine) per intake does not lead to greater protein synthesis. You will not get a greater anabolic bang for your Leucine buck beyond that point. I have included these two charts below to give you an idea of the Leucine content of the food and supplements you consume.  

(A) Leucine content of supplemental protein sources (Figure 3)

The numbers represent the grams of protein per 100g of protein from a particular source (not per 100g of powder). Let's say that if I am drinking a whey protein isolate product which has not been adulterated (e.g. hasn't been diluted with rice powder or maltodextrin. LOL) containing 30g of protein per serving. Based on this table I will be getting [(12.2/100)x30]=3.66g Leucine which is GOOD for GAINZZ!!

(B) Leucine content of food sources (Figure 4)

This table gives you the amount of popular foods you need to consume in order to reach the Leucine threshold. 

4. Don't get overzealous with Leucine

The discovery of the anabolic power of Leucine led to an excess of zeal among both supplement users and the supplements industry. Athletes rushed to consume higher amounts of Leucine by supplementing their meals and shakes with leucine in spite of having already reached the leucine threshold for that intake. At the same time, the supplements industry responded by commercialising BCAA products with extra Leucine, hence the birth of 3:1:1, 8:1:1 or even 10:1:1 BCAA ratios (Leucine: Isoleucine: Valine) and the rapid fading of the traditional 2:1:1 BCAA products. Because 10:1:1 is 5 times more anabolic than 2:1:1, right? WRONG!!

More leucine is not necessarily better. Going overboard with Leucine, both by increasing Leucine-alone intake or taking BCAA products containing a disproportionate amount of Leucine may lead to depletion of Isoleucine and Valine in the blood (not a good idea). If you are willing to bump up your leucine intake via a BCAA product, stick to a 2:1:1 product. 

There may be a benefit in adding BCAA to your whey shake if you are using less whey protein. In other words you do some "spiking". For instance, a study (Churchward-Venne et al., 2012) compared the anabolic effect of a 25g dose of whey protein (contains 3g Leucine) to a dose of 6.25g Whey protein with added Leucine (making 3g Leucine total). The results showed a similar anabolic effect but the effect was short lived. Therefore, forget about adding Leucine to a suboptimal dose of whey protein. Use the full on dose of whey protein instead. 

As I said in my 2013 article, don't forget that Leucine is only a trigger of anabolism. You need the other amino acids as well for muscle protein synthesis. 

Practical Recommendations

I have got success with with Dr. Norton's recommendation (PDF link in references section) of aiming for 3g Leucine per meal, spacing these meals by 4-5 hours. In between meals take a supplement of either 2-3g Leucine or 4-6g BCAA (2:1:1 ratio) either alone or along with carbohydrates depending on your caloric intake goals. A whey protein shake which is usually Leucine-rich may also work fine. For instance, if you eat breakfast at 6:00am, take Leucine as per above at 8:00am and then follow it up with another meal at 10:00am. This Leucine supplementation strategy may be a blessing for natural bodybuilders. Don't expect to blow up but if you are natty you will already be one who appreciates things that make a little difference to your physique. BCAAs and/ or Leucine can thus be implemented in both cutting and mass gaining programs. 

Other benefits of Leucine
Leucine has some other benefits which will be discussed in greater depth in other articles and I would like to mention some of them here. The anabolic properties of Leucine may be a blessing for the elderly as it helps in the preservation of muscle mass (Komar et al., 2015). Leucine in combination with vitamin B6 may also aid in boosting bodyfat loss (Zemel et al, 2012). Finally, Leucine in combination with HMB and creatine monohydrate can attenuate muscle atrophy caused by myostatin (Mobley et al, 2014).

It is very likely that John Bubb, Mr. Universe competitor
in the 60s consumes a leucine-rich diet. John, 80 years young,
contributes to our website via articles

References

Churchward-Venne, T.A., et al. Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. Journal of Physiology. 2012;590:2751-2765.

Komar B, Schwingshackl L, Hoffmann G. Effects of leucine-rich protein supplements on anthropometric parameter and muscle strength in the elderly: a systematic review and meta-analysis. J Nutr Health Aging. 2015;19(4):437-46.

Mobley CB et al. L-leucine, beta-hydroxy-beta-methylbutyric acid (HMB) and creatine monohydrate prevent myostatin-induced Akirin-1/Mighty mRNA down-regulation and myotube atrophy. J Int Soc Sports Nutr. 2014 Aug 13;11:38.

Norton, L., et al. Leucine content of dietary proteins is a determinant of postprandial skeletal muscle protein synthesis in adult rats. Nutrition and Metabolism. 2012;9:67.

Zemel, M.B., et al. Effect of a leucine and pyridoxine-containing nutraceutical on fat oxidation and oxidative and inflammatory stress in overweight and obese subjects. Nutrients. 2012;4;529.41.

http://www.sportsnutritionsociety.org/ArchivePDFS/ArchivePDFS-228.pdf

My Bio: I am a Mauritian originally from Roche Bois, Port Louis and now based in Cape Town, South Africa where I am busy with my postgraduate studies in molecular biology of exercise. My research, supervised by Prof. Edward Ojuka and Dr. Tertius Kohn, looks at the influence of nutrition and exercise in gene expression in muscle, research which is relevant and applicable to exercising individuals, sports persons and diabetic individuals. The knowledge that I share with you stems from my 18 years of experience in bodybuilding and 8 years (and counting) of university education in the field. I have also published work in the American Journal of Physiology: Endocrinology and Metabolism (2012, 2014), International Journal of Sport Nutrition and Exercise Metabolism (2013) and co-authored two book chapters on exercise and diabetes. I also presented my research work at the 2012 International Sports and Exercise Nutrition Conference (UK). I am grateful to each and everyone at the UCT Research Unit for Exercise Science and Sports Medicine. "Knowledge without sharing is worth nothing"

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