Leucine is Important, but How Much?

To see the increases you want to see from your workout program and hard work in the gym, you must consider things related to both your exercise program and your nutrition program.  The exercise side of things to gain muscle is somewhat straight forward, but not something that should ever be construed as easy.  Resistance training works best and you need to design your program to facilitate as much muscle growth as possible.  This consists of exercises that use a lot of muscle or looked at another way, exercises that involve the greatest number of joints in the body as possible.  Big boy or big girl exercises!  Squats, presses, deadlifts, lunges, pull-ups, etc. are the exercises of biggest concern.  Next you need to complete a relatively high volume of each exercise by completing at 3-4 sets of 10-12 repetitions.  Finally, you need to keep your rest down to lower levels, somewhere around 60 – 90 seconds between each set.  It’s hard work!  If you’re out of shape or not up for the task, you might not feel well after completing the first few exercises bouts, but studies indicate you will see changes.

Much is said on the nutritional front, but the two biggest factors appear to be your overall intake of calories and what proportion of these calories that are protein.  Consuming too many or too little calories can have deleterious outcomes relative to your ability to gain muscle and improve your body composition.  Certainly, eating too many calories against how many calories you are burning will result in weight gain.  If much of this weight is fat, your body composition and physique will actually get worse.  However, this presents a challenging situation because to gain muscle, you need consume enough calories on a daily basis to support these aspirations.  Eat too little, you may not gain muscle at all or the rate at which you gain muscle will be slower than you like, but swing too far in the other direction by eating too many calories and you may end up gaining muscle, but also gain too much fat.  You may be asking yourself, how many calories then should I consume and only general recommendations can be provided.  Starting points if you will and from there each person has to be diligent and pay attention to their diet, exercise habits and how their body is responding.  Depending on this response you should respond accordingly.

Outside of eating enough calories, consuming protein in the right amounts and at the correct time is also important.  How much protein to consume is a huge question and one that is beyond the scope of this article, but good general guidelines include: a) 20 – 30% of your total calories, b) 1.2 – 1.8 grams for every kilogram you weigh or c) eat a minimum of 20 – 30 grams of protein every time you eat (assuming you are eating 5-6 times each day.  Protein powder quality is critical and no source of protein is better than whey protein, but in particular, the leucine content appears to be something scientists are very interested.  Leucine is one of nine essential amino acids and other research has indicated leucine may play a key role in favorable changes in protein metabolism.  To better clarify the impact of essential amino acids and in particular the impact of ingesting more or less leucine in comparison to the other essential amino acids, a study was completed at the University of Texas in Galveston.  This study recruited older and younger participants and had them ingest an 8 ounces fluid solution that contained 6.7 grams of the essential amino acids (Katsanos, Kobayashi et al. 2006).  In one condition, the solution was 26% leucine, providing 1.7 grams of leucine.  These amounts are significant because they were intended to closely match the amount and proportion of leucine that is ingested when a whey protein is consumed.  The other condition provided 2.8 grams of leucine, which made its leucine content 41% of the total amount of essential amino acids.

These scientists were interested in answering two predominant questions: 1) does increasing the amount of leucine from what is provided in a typical whey protein invoke positive changes in muscle protein metabolism and 2) does the age of the participants impact how they respond.  The authors determined that the amount of leucine that was provided to younger participants had no particular impact.  In other words, the changes seen in muscle protein metabolism were similar in the young participants whether the amount of leucine was 26% or 41%.  In the young group, when both amounts of leucine were provided, significant increases in blood levels of amino acids occurred and they occurred very rapidly.  In fact, within 15 minutes of ingesting each solution, blood levels of the essential amino acids began to rise rapidly and within 30 minutes of ingesting each solution, the changes reached their peak levels.  In addition, rates of muscle protein synthesis reached peak levels similar regardless of whether the solution contained 26% or 41% leucine.

Interestingly when both amino acid solutions were provided to the group of elderly participants (average age of 66 years), the solution which contained a greater percentage of leucine was the only group which resulted in peak levels of amino acids in the blood as well as rates of muscle protein synthesis.  These findings nicely coordinated with other studies that have indicated that as a person reaches advanced age, the amount of leucine and other amino acids that are needed appears to increase.  For some reason that scientists can’t quite explain, the amount of leucine and other essential amino acids that are needed to maximally stimulate rates of muscle protein synthesis increase with age.  If you’re young, however, a simple dose of whey protein appears to provide enough leucine and the other essential amino acids to maximally increase amino acid levels in the blood and increase muscle protein synthesis.


Katsanos, C. S., H. Kobayashi, et al. (2006). “A high proportion of leucine is required for optimal stimulation of the rate of muscle protein synthesis by essential amino acids in the elderly.” Am J Physiol Endocrinol Metab 291(2): E381-387.