Leucine: The Protein Game Changer

Protein is getting almost as bad of a rap as carbohydrate these days; either we eat too much or not enough! If these proclamations are based on the US dietary references, then it may indeed appear that we consume too much. However, the amount of protein recommended in those reference ranges are not for competitive athletes training > 7 hrs/week, average volume for a triathlete preparing for an Olympic distance triathlon.
Klean Athlete Whey Isolate PowderLeucine is an amino acid that initiates the creation of protein. The amount of leucine recommended to trigger protein synthesis is between 2.0 – 3.0 grams, which is found in approximately 20 – 30 grams of protein. More is not better in this situation because your body cannot assimilate more than 25-30 grams of protein at one time. When planning your protein intake for the day, focus on protein sources of high biological value (eggs, low-fat milk, meat, non-GMO soy isolate) for the most leucine for your buck. Plant-based protein sources are environmentally sustainable alternatives for vegan athletes, but will require a higher total intake of essential amino acids.

If you aren’t vegan, you can combine whey and casein to maximize your recovery. Whey protein is absorbed and assimilated the quickest, and has the highest leucine content per serving. Ingesting the the high leucine content will initiate protein synthesis quickly, ensuring adequate recovery form your workout. Whey isolate is the better choice for quality compared to concentrate. Casein and soy protein take longer to digest and should be consumed in 1- 2 hrs post workout. In general, the daily protein recommendation for endurance & strength athletes is 1.2 – 1.7 grams/kg (2.6 – 3.7 grams/lb) for training with at least 15 grams of that for recovery. Per pound that is a lot of protein and I only recommend this during days of double workouts or very high intensity.

now_foods_branched_chain_amino_acid_powder_340g_12oz_bcaa__12481.1367919587.1280.1280BCAA supplement facts label: Leucine, Isoleucine, Valine






To determine if you are already consuming 2.0 -2.5 grams of leucine, refer to the list below. Unfortunately, unless it is an amino acid supplement, leucine will not be listed on a supplement facts label. [Amounts and calculation made from the NutriBase nutrition facts database and USDA Nutrient database.]

  • BCAA supplement (5.0 -5.6 grams) ~ > 2.5 g leucine
  • 1 scoop of whey protein (20 – 25 g)  > 2.0 – 2.5 g leucine
  • Soy Isolate Powder (Supro): 1 scoop (28.3 grams)  > 6.7 – 7.2 g leucine
  • 30 oz. (900ml) dairy/non-dairy milk  > 2.0 – 2.5 g leucine
  • 3 whole eggs  > 2.0 – 2.5 g leucine
  • 8 – 10 slices of whole wheat bread > 2.0 – 2.5 g leucine
  • 400 grams of tofu (14 oz container) > 2.0 – 2.5 g leucine
  • 300 – 400 grams yogurt (17 – 20 oz) > 2.0 – 2.5 g leucine
  • 770 grams (~1.7 lb)  bison > 2.5 – 3.0 g leucine


As with all supplements, quality & contamination are of concern. Many protein powders have contained metals (arsenic, lead or mercury) and often the percent of BCAA’s or grams of carbohydrate and cholesterol listed on the label, is not the same as in the container. There is no simple way of knowing which to choose except for following products labeled with the NSF verification icon. This is not 100% guaranteed but the NSF Certified for Sport is a good place to start.


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