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The Leucine Thread



Feb 19, 2011
Do a quick search on Leucine and you will quickly discover a wide variety of articles (and speculative threads aka broscience) proclaiming it as the end all be all of amino acids. This is even "scientifically proven." Since I am an anal retentive micromanaging control freak I figured I would try my best to organize many of the best articles here, and in way to draw some conclusions, cutting through the bull if you will.

To start, here is what I "know" about leucine, boiled down.

- Leucine is one of the Branched Chain Amino Acids (BCAAs).
- so-called "proper" proportion of leucine to isoleucine and valine is 2:1:1.
- Leucine is responsible for much or most of the muscle protein synthesis (MPS) accredited to BCAAs, and to a certain extent this is proven.
- Leucine supplementation alone will not create an environment for maximal MPS because other amino acids are required to sythesize muscle.
- BCAAs, EAAs and mixed AAs provide only limited stimulation for MPS without sufficient blood glucose levels.
- High blood sugar levels are more anabolic than high blood AA levels.
- 3-4g leucine are sufficient to stimulate maximal MPS.
- More than 3-4g leucine provide no additonal MPS stiulation, and might hinder MPS.
- the MPS effect of leucine appears to last about 2 hours.
- additional leucine, BCAA, EAA, mixed AAs or combined protein taken within 4 hours does not stimulate additional MPS.
- Additional carbs taken at the 2 hour mark DOES stimulate additional MPS, provided blood AA levels are still high. Additional leucine at this time does not increase the effect.
- It take between 1 and 2 hours for blood AA levels to peak after consumption, depending on method of intake, e.g. whey shake, cottage cheese, fish, meat, etc.
- It takes about 15-20 minutes for simple sugar to begin stimulating insulin production.
- Whey, EAA and BCAA consumption rises blood AA levels for about 2 hours.
- Casein and whole protein consumpion rises blood AA levels for about 5 hours.

So lets put this in context.

Taking a pre-workout shake at 30 minutes prior puts the amino acid peak right in the middle of the typical workout, the insulin produciton at the beginning of the workout, and the end of the blood AA level increase shortly after the workout ends (30 mins or so).

Eating a whole meal, or even just 2 cups of cottage cheese, 1 1/2 hours before workout places the amino peak at the beginning of the workout (coinciding with the whey shake insulin spike),and the end of the window 1 1/2 hours after the workoutends.

A post workout whey shake takes an hour to significantly rise blood AA levels, which means for those folks trying to his that mythical "1-hour post workout window" you have already missed it if you wait until post workout to consume protein.

When your body is full of nutrition it absorbs less. When your body is starved of nutrition is absorbs more. Therefore you want to force your body to be nutrition starved for just a moment before giving it what it wants in orderto maximize absorption/use.

Given these points, the pattern of circa workout nutrition becomes more apparant. This feeding plan is based on the timing and duration of effect for leucine and insulin. The goal is to consume nutrients in sufficient quantity to trigger MPS, but not consume nutrients when the body is not best able to use them (wasting them?).

1. whole meal with whole protein, or at least 2 cups of lowfat/nonfat cottage cheese and a complex carb, 1 1/2 hours before training. This meal should include enough mixed and complete protein to raise blood AA levels, approx 20-30g, and enough complex carbs to total 2X the protein. Additional leucine at this point would be counterproductive. We do not want the leucine trigger to signal quite yet. Blood AA levels peak at the start of training and begin to fall 1 1/2 hours post training.

2. whey and simple carb shake 30 minutes prior to training. This meal should include enough protein to provide 4g leucine as the leucine trigger, about 35-40g whey protein, and enough simple carbs to signal the insulin spike, about 1 1/2 to 2X the amount of protein. Blood AA levels peak half hour into training and begin to fall 1 hour post training.

3. whey and simple carb shake 20-30 minutes post training. Additional leucine at this time is not beneficial, but total AA level is, so 20-30g protein is required, as well as enough simple carbs to stimulate a second insulin spike, again about double the amount of protein consumed. Blood AA levels peak 1 1/2 hours post training and begin to fall 3 1/2 hours post training.

4. a complete meal, or at least another 2 cups of cottage cheese, 1 1/2 hour post workout. This meal should provide another 30-40g protein and twice that amount of complex carbs. Blood AA levels peak at 3 hours post training and begin to fall 8 hours post training.

5. a whey and simple carb shake at 2 1/2 hours post training providing enough simple carbs to spike insulin, approximately 25-35g, will take advantage of the steadily high blood AA levels and stimulate an additional 2 hours of MPS. Protein should provide 3-4g leucine, which is 35-40g whey.

So using this feeding pattern we have consumed 130-175g protein while stimulating MPS at 3 times for 2 hours each: 1] start of training, 2] 1 hour post training, 3] 3 hours post training. At this point in my schedule I'm headed for bed, but if you train earlier in the day you have an opportunity to stimulate a 4th MPS by consuming a simple sugar shake at 4 1/2 hours post training. You can add whey, but a slower protein source might be more appropriate if you are headed for bed shortly thereafter. I add my cottage cheese with the previous simple sugar shake.

In this way I get half of my daily protein during the post training window, with consistently high insulin levels pushing sugar and protein into my muscle cells.


Senior Member
Feb 14, 2011
Most effective leucine dose may be as high as 20 g

Do you add leucine [structural formula shown below] to your protein shakes to give them more bite? And are you satisfied with the results? You’ll probably be even more satisfied if you increase your dose. In a review article on the anabolic effects of amino acids we came across a couple of pretty interesting facts about the muscle-strengthening effect of leucine.


Leucine is an interesting amino acid. If you give muscle cells leucine they start to produce more muscle proteins. How this works is not yet known, but the effect is noticeable enough that sports nutrition manufacturers have introduced leucine products onto the market.

Leucine retains muscle mass if you are unable to use your muscles. If you add leucine to a shake containing carbs and proteins, it’ll boost your muscle protein production. Adding extra leucine to meals reduces muscle breakdown in the elderly.

Leucine only works if you use it in combination with proteins or amino acids. If you consume it on its own, or in combination with carbs, it has no effect. Not even in strength athletes. [J Strength Cond Res. 2010 Aug; 24(8): 2211-9.]

It’s still not clear, however, what the optimal dose should be. The earlier studies suggested a minimum dose of 3 g for healthy people and probably a higher intake for elderly people. Since then natural bodybuilders have started taking 5-8 g doses of leucine. But in an article that researchers at the University of Nottingham published in the Journal of Nutrition in 2006, we found a figure that suggests that even these doses are on the low side.

The figure is based on experiments in which the researchers fed their – inactive – subjects leucine intravenously. Their muscle tissue rate of production increased most when they were given an hourly dose of 0.261 g per kg bodyweight. Suppose that all the leucine you take orally reaches your bloodstream, then someone weighing 85 kg would need about 22 g leucine to derive maximum benefit from it.

The article also mentions that amino acids will only increase your muscle protein production by a factor of 2-3. Whether this remark is relevant for all three readers of this web magazine, we have our doubts. Athletes’ muscles are continuously recovering and growing.


Feb 19, 2011
Good post, but I hesitate to use ingested data and IV data interchangably. The data I've seen shows that 8g leucine, ingested as L-Leucine, stimulates MPS about 1/3 less than 4g.