In this post, we will take a look at the differences between protein supplementation and amino acids, and see which one is better for building muscle.

Whey protein and leucine – both have been hailed as the ultimate muscle building supplements. But, in a recent study, the effects of whey protein and leucine on muscle strength were compared in healthy young men. The research found that whey protein did not promote muscle strength as effectively as leucine, which provides a more sustained release of amino acids and an enhanced anabolic response.

Whey protein is one of the most successful supplements for building muscle mass. Leucine is one of the most important amino acids for muscle recovery and growth. The purpose of this article is to compare whey and leucine. We will discuss: what leucine is; how it is affected by whey protein; and whether leucine is better than whey protein for building muscle.

Leucine is the king of amino acids when it comes to muscle growth. It has its own VIP entrance to the cells, and when it arrives, the DJs mTOR and Rheb kick off the protein production celebration. Is leucine, on its own, superior to whey?

Do you want to bulk up your muscles? If that’s the case, make sure you’re putting on more muscle (muscle protein synthesis) than you’re losing (Figure 1, below).


You’ll need two things for this:

  1. exercise (specifically, resistance training) and
  2. a mixture of amino acids (transported in blood).

The exercise stimulates the muscle to begin producing proteins.

The building blocks of muscle are amino acids. If amino acids are present, your muscles will begin to build additional muscle. However, there will be no protein synthesis if amino acids are not available (more precisely, no net protein synthesis).

In recent years, scientists have become increasingly curious about which proteins/amino acids are ideal for muscle growth during and after an exercise.

It started with whey protein vs. casein protein (or other proteins). In this scenario, whey wins because the amino acids in whey are absorbed more quickly by the body.

Then researchers discovered that certain amino acids, known as branched chain amino acids (BCAAs), were better in building muscle.

Leucine (a type of branched chain amino acid) appears to be the key to muscle protein synthesis now (making muscle).

Amino acids are the building blocks of proteins.

You can get a sense of what an amino acid is by looking at Figure 2 below, which is my simplified artist’s rendition of one. Amino acids, in my mind, are made up of bricks of various forms and sorts that snap together to form various amino acids.


All amino acids, you see, have two distinct blocks (groups):

  1. A category of amino acids
  2. An acid group (also known as a carboxyl group)

As a result, amino acids are produced.

But there’s more: amino acids have an optional group that distinguishes them from one another.

Glycine is my personal favorite. Why? Assume you had a biochemistry exam and were required to draw glycine. All you’d need to remember is the structure of an amino acid and an H. (hydrogen). Take a look at Figure 2 to see what I mean. Glycine is not just my favorite amino acid, but it is also the most basic.

Other amino acids have optional groups that are more complicated (usually called side groups). Branched chain amino acids are one type of amino acid (BCAAs).

What is a branched chain amino acid, and what does it do?

Branching chain amino acids have branched optional groups, whereas simple glycine has a hydrogen as an optional group. The three branched chain amino acids are depicted in Figure 3 below (leucine, isoleucine and leucine). There are a lot more CH3 (methyl groups) poking out or branching as you can see.


What distinguishes leucine from other amino acids?

Why am I focusing on leucine in particular? You already know that I’m an amino acid snob. My biochemistry tests, on the other hand, have nothing to do with why leucine is unique. Leucine is unique in that it is the rock star of amino acids… at least when it comes to muscle.

The rock star of amino acids is leucine.

Yes, leucine is the rock star of amino acids, with its own VIP entry into the muscle (cell) and DJ-like appeal. This is arguably the most straightforward example for understanding the universe of muscle cells.

A membrane separates the interior from the outside of all cells, keeping the internal stuff within and the outside stuff outside. (It’s worth noting that cell membranes are largely formed of fat [phospholipids], which is one of the reasons why eating adequate fat is crucial.)

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Once leucine has entered the club (cell), it can be passed on to the DJs (mTOR and Rheb proteins), who are in charge of kicking off the party (protein synthesis). So, “Hey dude, start protein synthesis!” say mTOR and Rheb. (I’ll go into greater detail in a future research review.)

Leucine is the only amino acid that we know of that can directly activate mTOR and Rheb. This elevates leucine to the status of rock star (or, if you prefer, Paris Hilton, though I believe this is an insult to leucine).



Question for investigation

Okay, leucine is a superstar amino acid, but do you really need more than what’s currently in whey protein? Is leucine superior to whey in terms of boosting protein synthesis and anabolism in general?

The goal of this study was to see if adding leucine to whey protein intake before exercise boosted the benefits.

However, there is one significant defect. Try to figure it out, and I’ll reveal the answer at the end. There will be no cheating! Imagine it as a game of Clue.

Colonel Mustard wasn’t in the conservatory with the candle stick, either.


The following is the study that will be discussed this week:

KD Tipton, TA Elliott, AA Ferrando, AA Aarsland, RR Wolfe. Resistance exercise and consumption of leucine and protein stimulate muscle anabolism. 2009 Apr;34(2):151-61 in Appl Physiol Nutr Metab.


(No, that wasn’t Miss Scarlett with the rope in the kitchen.)

For this study, the typical suspects — uh, I mean volunteers — were enlisted. Men (11) and women (4) were healthy and young (25-30 years old), yet they had 5 years or more of regular resistance exercise (most likely weight training), which is unusual. (Subjects are frequently uneducated.)

There were several parts to the experiment:

  1. Researchers calculated the individuals’ 1 repetition maximum (1RM) for leg extension 5 days before the test day.
  2. All participants went to a clinical research center the night before the test day, ate a typical dinner, and then just drank water until the study began the next morning.
  3. On test day, venous and arterial blood samples were taken first thing in the morning (at the ludicrous hour of 5:45 a.m.).
  4. After that, muscle samples of the vastus lateralis (outer quads muscle) were collected (about 50 mg of muscle).
  5. The placebo (artificial sweetener, flavoring, and water) or whey (16.6 g) and leucine were given to the participants (3.4 mg).
  6. After drinking the placebo or whey + leucine drink, the participants immediately began leg workouts.
  7. Leg extensions were performed for 10 sets of 8 repetitions at 80% of 1RM with 2 minute rest between sets (total time spent, about 35 min).
  8. During and after the leg exercise, blood and muscle samples were obtained.


(It wasn’t Mrs Peacock with the knife in the lounge.)

The combination of whey and leucine raised blood insulin levels.

Insulin levels were higher in the whey + leucine group from just before consuming the placebo or whey + leucine drink until around 120 minutes after exercise, when insulin levels were returned to baseline.

How much higher can you go? Whey+leucine had 1944mU/mL, compared to 386mU/mL for the placebo (for those interested, this is a sum of the area under the curve from pre drink to 120 minutes post exercise).

In other words, blood insulin levels in the whey+leucine group were over 5 times greater than in the placebo group!

Raising insulin levels may appear to be a bad thing, and you don’t want high circulating insulin levels most of the time. The muscles, on the other hand, are particularly vulnerable to the effects of insulin just after an exercise. Insulin will be most effective at that time, driving nutrients (such as protein) into the cells. As a result, elevated insulin levels are acceptable for a short period of time.

Amino acids in the blood after drinking

Following exercise, the amounts of isoleucine, phenylalanine, leucine, lysine, and threonine in arterial blood increased. Overall, they were higher (as measured by the area under the curve) in the whey+leucine group, whereas none of the amino acids increased in the placebo group.

As a result, the whey+leucine drink boosted post-exercise arterial amino acids (which is very important for protein synthesis in the muscle).

There was no difference between the groups in terms of muscle amino acids.

Here’s the thing: there’s a big difference between the two. Despite the fact that the whey+leucine group had more amino acids in their blood than the placebo group, there was no difference in amino acid concentrations in the muscle (as measured by the biopsy).

This, I believe, is due to the fact that your muscle manages the amount of amino acids it requires at any one time and draws in more as needed.

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Professor Plum was the one who misinterpreted the results in the study.

The study found that taking 16.6 g of whey protein and 3.4 g of leucine before resistance training simulates the muscle anabolic process better than placebo. The muscle has more amino acids available to it (since the blood has more).

By comparing a prior study, the authors conclude that whey protein plus leucine had the same anabolic effect as whey protein alone (1).

In conclusion

The researchers didn’t have a whey-only group or a leucine-only group, as most of you have undoubtedly realized, which is the study’s weakness. If you don’t have a group without whey or leucine, how can you tell if leucine improves muscle anabolism?

Having a placebo group is beneficial. A whey+leucine group is beneficial. However, you have nothing to compare the effect of leucine on its own. You simply understand that whey+leucine is preferable than nothing.

The authors compare this study to one they conducted with only whey (which contains leucine) and claim that the findings are similar. Okay, this may be true, but it was a different period, and things may have been different (unintentionally). They’ve established that whey+leucine is better than nothing, but the amount of leucine that needs to be added is yet unknown.

Knowing this bunch of researchers and their previous work, they will undoubtedly look at this study and see if leucine has any further anabolic effects than whey.


To see the information sources mentioned in this article, go here.

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Leucine is an amino acid that comes from the proteins found in foods such as meat and dairy, and is a primary building block of muscle. Leucine has been heralded for its role in muscle growth, and has been shown to promote muscle synthesis and recovery. However, it has been suggested that leucine may be the most important amino acid for athletes in the post-workout period to promote muscle growth. In this review, we explore the current evidence linking leucine to muscle growth, and discuss the potential benefits of using whey protein supplements in the post-workout period.. Read more about how many grams of leucine in whey protein and let us know what you think.

Frequently Asked Questions

Is leucine good for building muscle?

Leucine is a branched chain amino acid that is found in high levels in protein-rich foods like whey, eggs, and beef. It has been shown to have anabolic properties which can help build muscle mass.

Does leucine increase protein synthesis?

Yes, leucine is an amino acid that has been shown to increase protein synthesis.

How much leucine should I take daily to build muscle?

You should take around 2-3 grams of leucine daily in order to build muscle.

Related Tags

This article broadly covered the following related topics:

  • leucine
  • leucine protein synthesis
  • when to take leucine
  • l leucine powder benefits
  • leucine benefits
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