Low Dose Leucine Just as Potent as Whey for Stimulating Protein Synthesis

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Low Dose Leucine Just as Potent as Whey for Stimulating Protein Synthesis

by: Robbie Durand

Leucine is a key amino acid involved in the regulation of skeletal muscle protein synthesis.  Leucine triggers the anabolic mTOR pathway, which is essential for muscle growth; additionally, leucine has proven to build muscle, maintain lean mass when in a caloric deficit, and boost recovery. In a previous study, researchers found that small doses of leucine is a super potent anabolic agent. Researchers wanted to examine how adding leucine to a protein drink would affect muscle protein synthesis. Researchers assessed the effect on muscle protein synthesis at rest and after resistance exercise. The men completed unilateral knee extensor resistance exercise before the ingestion of various intakes of whey protein, BCAAs, and leucine:

The subjects received either:

  • 25 grams of whey protein (which contained 3.0 grams leucine).
  • 6.25 grams of whey protein (which contained 0.75 grams leucine).
  • 6.25 grams whey protein supplemented with leucine (3.0 grams total leucine).
  • 6.25 grams whey protein supplemented with leucine (5.0 grams total leucine).
  • 6.25 grams whey protein supplemented with leucine, isoleucine, and valine (5.0 grams total leucine).
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These results, indicating that high leucine can have enhanced muscle anabolism effects, are important for athletes who are on a strict diet and cutting back on total calories.

One would expect that the 25 grams of whey protein group would have the biggest impact on muscle protein synthesis but that’s not what the researchers found. The really interesting finding was the low protein (6.25 grams) with high leucine (5 grams) mixed beverage was as effective as a high-protein whey (25 grams) shake at stimulating increased muscle protein synthesis rates when supplemented with a high amount of leucine (five grams). These results, indicating that high leucine can have enhanced muscle anabolism effects, are important for athletes who are on a strict diet and cutting back on total calories.  So for bodybuilders looking to remain anabolic throughout the day, one may consider taking some leucine throughout the day, even if its a small amount.  A new research study published this month reports that a little bit of leucine is just as effective as stimulating muscle protein synthesis as whey protein powder.

Acute muscle protein synthesis increased similarly after whey protein and low-dose leucine-enriched essential amino acids.

This study was conducted in older women to reduce muscle wasting.  Researchers examined the effects of two feeding regimes in older women:

  • whey protein (20 grams) or
  • low-dose leucine-enriched essential amino acids (EAA) [3 grams of leucine (40% leucine).

Researchers examined muscle protein synthesis, insulin/amino acid concentrations, muscle microvascular blood flow, and muscle anabolic signaling at baseline and in response to both resting feeding and feeding plus exercise. The subjects performed 6 sets × 8 knee extensions at 75% 1-repetition maximum. At the end of the study, plasma insulin  and essential amino acids were markedly greater after whey protein than low-dose leucine-enriched essential amino acids. Neither low-dose leucine-enriched essential amino acids nor whey protein modified leg blood flow in response to resting feeding or feeding and exercise, whereas muscle blood flow increased to a similar extent in both groups only after feeding and exercise. In response to resting feeding, both whey protein and low-dose leucine-enriched essential amino acids equally stimulated muscle protein synthesis 0-2 hours, abating thereafter (0-4 hours). In contrast, after feeding and exercise, muscle protein synthesis increased at 0-2 hours and remained elevated at 0-4 hours with both whey protein and low-dose leucine-enriched essential amino acids. Acute muscle protein synthesis increased similarly after whey protein and low-dose leucine-enriched essential amino acids. Older women remain subtly responsive to nutrition and exercise. Intriguingly though, bolus whey protein offers no metabolic advantage over low-dose leucine-enriched essential amino acids. So if your not into whey protein drinks, the good news is that you can get the same effects with a leucine and essential amino acid drink.

Bukhari SS, Phillips BE, Wilkinson DJ, Limb MC, Rankin D, Mitchell WK,
Kobayashi H, Greenhaff PL, Smith K, Atherton PJ. Intake of low-dose leucine-rich
essential amino acids stimulates muscle anabolism equivalently to bolus whey
protein in older women at rest and after exercise. Am J Physiol Endocrinol Metab.
2015 Jun 15;308(12):E1056-65.

Churchward-Venne TA, Breen L, Di Donato DM, Hector AJ, Mitchell CJ, Moore DR,  Stellingwerff T, Breuille D, Offord EA, Baker SK, Phillips SM. Leucine
supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: a double-blind, randomized trial. Am
J Clin Nutr. 2014 Feb;99(2):276-86.

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