BCAAs during cutting

Geschatte leestijd: 7 minutenIn this third and final part of this series, I compare the different BCAAs leucine, valine, and isoleucine. Additionally, I discuss the potential value of BCAAs during “cutting,” which involves losing weight while maintaining muscle mass.

BCAA’s?: Why not just Leucine?

In the previous part, I mentioned that you may wonder if BCAAs contribute to more muscle growth (by limiting muscle breakdown) when your diet throughout the day and around your workout is already adequate. Another question you can ask yourself is the added value of valine and isoleucine. You may have already noticed in the previous parts that leucine is often mentioned separately.

I myself mentioned wanting to see the ratio in favor of leucine in BCAAs. In the only studies I considered relevant, only leucine was used. This is because leucine has functions that valine and isoleucine do not: activating mTOR and increasing insulin.

Leucine exhibits strong insulinotropic characteristics, which may increase amino acid availability for muscle protein synthesis, reduce muscle protein breakdown, and enhance glucose disposal to help maintain blood glucose homeostasis.

J. Manders, Catholic University of Leuven [1]

Leucine and Insulin

Insulin is anabolic. It is released when there is a lot of glucose (sugar) in the blood. Insulin signals muscle cells to store more sugars as glycogen in the muscles and to produce more protein for muscle growth. Leucine causes an increase in insulin, thereby achieving these benefits [1,2,3]. However, insulin also allows sugars to be stored as body fat, a point that will be addressed later in this article.

Leucine and mTor

BCAAs (leucine, isoleucine, and valine), particularly leucine, have anabolic effects on protein metabolism by increasing the rate of protein synthesis and decreasing the rate of protein degradation in resting human muscle. Also, during recovery from endurance exercise, BCAAs were found to have anabolic effects in human muscle. These effects are likely to be mediated through changes in signaling pathways controlling protein synthesis.

E. Blomstrand, Åstrand Laboratory, University College of Physical Education and Sports [15]

The above quote also specifically points out the anabolic effect of leucine and refers to the likely cause: “signaling pathways controlling protein synthesis.” mTOR stands for mammalian target of rapamycin or nowadays also referred to as mechanistic target of rapamycin (don’t worry, this question won’t be on the test). mTOR is a protein that plays a crucial role in initiating the production of more protein in the muscles. It responds to growth hormone and insulin, but also to leucine (4,5,6). To keep a long story short, I will suffice it to say that of the three BCAAs, only leucine has this effect and thus distinguishes itself from valine and isoleucine.

Another distinction is that isoleucine and valine can be converted into glucose. Leucine cannot, but it can be converted into ketone bodies to provide energy [16].

Isoleucine

Isoleucine also lowers blood glucose levels by allowing the muscles to take up more glucose. However, isoleucine does this without the action of insulin (which is not increased as with leucine) and without the action of mTOR [7]. The increase in protein synthesis caused by insulin elevation, which leucine induces, is absent with isoleucine. The benefits achieved by isoleucine include:

• More fuel to the muscles, reducing the need for protein breakdown in the muscles.
• Less glucose that can be converted into body fat.

Valine

Valine plays an important role in regulating energy supply and protein synthesis, but that doesn’t necessarily mean it’s a positive role. It turns out that valine actually decreases glucose uptake by the muscles [doi]. This seems to be a system of negative feedback, acting as a limiter on glucose uptake. There seem to be no studies where the effect of intake of only valine on muscle mass and/or strength has been examined. The added value of extra valine intake is therefore unknown.

Leucine reduces valine and isoleucine

Aside from the effect of isoleucine, there is another reason not to use only leucine as a supplement.

Leucine appears to work antagonistically on valine and isoleucine. When you take leucine, the amount of valine and isoleucine is decreased, resulting in limited growth [8,9,10,11]. For example, the addition of 3% to a diet low in protein (9% casein) in rats resulted in limited growth [10]. This growth limitation was reversed by adding isoleucine. Researchers saw a similar effect in a comparable study in 1956 [9]. In that study, the growth suppression caused by 3% leucine was lifted by adding valine and isoleucine.

These observations indicated that excess leucine increased the requirement for isoleucine and valine in the rat.

A.E. Harper

However, we see different circumstances here than normal when there is enough food intake. This involved a diet with low protein. The negative influence of ingested leucine on existing valine and isoleucine levels led to a deficiency in valine and isoleucine. Various studies show that this effect of leucine is reversed when enough food is eaten [8].

The amounts of valine and isoleucine needed to compensate for the effect of leucine are also very small. A diet consisting of 5% leucine required only 0.16 isoleucine and 0.15% valine to be added. You can imagine that with the addition of normal protein, you end up with proportionally much higher doses of isoleucine and valine. You already reach these amounts very quickly from normal food intake.

BCAAs and Cutting

So far, the relevant studies do not seem very positive. There may be an exception. During cutting, when you want to burn body fat without losing too much muscle mass.

As mentioned, we do see a positive effect of BCAAs, especially leucine, when there is a shortage of food. This is the case when “cutting,” consciously consuming fewer calories than the body actually needs. Eating very few carbohydrates (but also fats that can be converted into sugars) causes little insulin to be produced. Otherwise, there would be too little sugar in the blood, possibly resulting in a “hypo.” Less insulin means less body fat, but also less protein synthesis. This also comes at the expense of your muscle mass. For this reason, some people see the added value of BCAAs to limit muscle breakdown by ensuring the presence of sufficient amino acids in the blood.

Firstly, you may again wonder to what extent regular protein intake would not lead to the same effect. Moreover, I have just explained above that leucine increases insulin levels. Something you may not necessarily want when cutting.

Whey protein also has an insulin-increasing effect [12,14]. This applies even more to hydrolyzed protein, whether it’s whey or casein [13]. “Normal” casein protein has no insulin-increasing effect [14]. To limit muscle mass during the cutting phase, I would therefore not use BCAAs, especially leucine, but casein.

A small exception may be isoleucine. As seen, this lowers blood glucose without increasing insulin. Glucose that cannot be converted into body fat. However, you could achieve this by eating less. The latter is cheaper, but mentally it may be pleasant to be able to eat a little more and compensate with isoleucine.

Conclusion

And what about Jay?

I started the first part of this series with Jay Cutler mentioning to me Protein and BCAAs as his two favorite supplements. Honestly, I’m less convinced and enthusiastic.

However, who am I to say that a four-time Mr. Olympia is wrong? Well, first of all, someone who doesn’t sell BCAAs himself. I was actually a bit surprised by his answer. I asked the question about his two favorite supplements, thinking I would get the expected answer: Protein and creatine.

Dorian Yates mentioned protein and a pre-workout and still couldn’t resist mentioning a third, namely the familiar creatine. Even when mentioning the pre-workout, I didn’t get the impression that there were commercial interests at play, since he immediately said that in his time the pre-workouts were composed themselves (rather than referring to one of his own pre-workouts).

In this respect, it may be good to know that creatine doesn’t have particularly high profit margins. It’s cheap to produce, made and sold by everyone, and used in relatively small quantities. It’s possible that BCAAs yield higher profit margins and explain Jay’s answer. However, ultimately, it’s also possible that Jay simply knows something I don’t.

Based on the many studies, however, I see no significant added value of BCAAs when enough food is eaten, especially enough protein.

References

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2. Koopman R, Wagenmakers AJ, Manders RJ, Zorenc AH, Senden JM, Gorselink M,Keizer HA, van Loon LJ. Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects. Am J Physiol Endocrinol Metab. 2005 Apr;288(4):E645-53. Epub 2004 Nov 23. PubMed PMID: 15562251.
3. Kalogeropoulou D, Lafave L, Schweim K, Gannon MC, Nuttall FQ: Leucine, when ingested with glucose, synergistically stimulates insulin secretion and lowers blood glucose. Metabolism 2008, 57:1747-52.
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