What is Leucine?

Leucine is an essential amino acid, which means humans cannot make it on their own (cannot be synthesized) and it must be obtained from foods we eat.  It is found in meats, dairy products, beans and legumes. It breaks down into Acetyl-CoA and Acetoacetate; one of the two ketogenic amino acids in humans.

This branched chain amino acid (building blocks of protein) is very unique in that it helps activate new muscle protein synthesis, helps regulate blood-sugar levels, growth hormone production and wound healing.  Leucine has been shown to:

  • Prevent or decrease the net rate of protein breakdown
  • Improve both mental and physical performance
  • Have a sparing effect on depletion of muscle glycogen stores (energy within skeletal muscle)

How much Leucine should you eat?

It has been shown that muscle does not build itself as quickly when leucine is taken alone. A study that came out in 2018 in Clinical Nutrition ESPEN looked to study the difference between leucine supplementation alone and leucine within a whey protein mixture on aged mice.  It was found that muscle protein synthesis pathways were 1.6X greater with the whey protein mixture rather than leucine alone and peaked at the 60 minute mark. It is thought there is a ‘desynchronization’ between the building blocks (substrates) needed to increase muscle mass and the Leucine signal when there is no other substrate in the mix.

But wait, you may be thinking, this was only seen in mice!  Another article published in 2017 in Clinical Nutrition Journal tested a similar hypothesis on women in their 60s. It was found that just 1.5g of Leucine can provide (perhaps maximal) stimulation of muscle protein synthesis. Other articles have shown that 3g of Leucine alone stimulates protein synthesis in young men.

An additional study showed that one can obtain muscle protein synthesis as long as the leucine content is sufficient and this can be very beneficial in older populations since it becomes more difficult to eat large amounts of food as we age.

Additional Benefits of Leucine

There are the obvious benefits with muscle retention and synthesis utilizing Leucine, but what other not-so-obvious benefits are there to eating an adequate amount of Leucine?

  • Leucine supplementation has been shown to reduce atherosclerosis:  In 2016, an experiment was done analyzing the cholesterol levels of mice with leucine supplemented water and a 51.77% reduction of liver cholesterol content.  It improved the plasma lipid profiles and reduced overall systemic inflammation in these mice.
  • Increase in SIRT activity by 30-50% (SIRT is an enzyme pathway associated with healthy aging processes/longevity):  SIRT helps fight inflammation, fat synthesis and storage.  Thus, by increasing the activity of this enzyme you can help reduce the effects of aging on your cells.

Why is this important?  As we age, our nutritional needs intensify.  One important aspect of a decreasing appetite is losing muscle mass, the clinical term is known as ‘sacropenia.’ If you don’t have enough muscle mass it becomes harder to do daily life activities and can result in dependence on caregivers, etc…Resistance training plus whey protein with supplementation of leucine at rest and after exercise has shown to build and maintain skeletal muscle.

Not Just For Bodybuilders

For fitness enthusiasts and bodybuilders it is known to take Leucine to maximize muscle synthesis and preservation. For people who are just starting on their weight loss journey or are looking to maintain youth, it is essential to recognize the importance of having a complete whey formula with enough Leucine to rely on a day to day basis.

The John’s Killer Protein® Difference

If you look at standard protein mixtures you will find vitamins, biotin, folate, thiamin, magnesium, etc.  However, most protein brands lack the proper dosage of essential amino acids forcing most to purchase separate amino acid supplements.   A protein mixture that lacks proper dosage of essential amino acids defeats its whole purpose of trying to preserve and build muscle mass in the first place!  Why pay for extra essential amino acids when you can find a whey protein blend that already has optimal doses of leucine in it already.  This is what makes John’s Killer Protein® different – our blends all naturally contain the optimal dosage of essential and branched chain amino acids.

The first study mentioned emphasized the importance of Leucine within a whey protein mixture and this is exactly how John’s Killer Protein® is formulated.  Numerous supplements require you to supplement the supplement itself.  Many athletes are taking protein and BCAAs separately, but this should not be the case.  John’s Killer Protein®’s entire formulation is set up for everyone from competitive athletes to individuals who are trying to maintain and build more muscle – which everyone should be striving to do!


Leucine is an extremely important essential amino acid that triggers and helps regulate new muscle protein synthesis.  Leucine has been shown to being more effective when consumed in proper dosage and as part of a complete whey protein blend.  to maximize the benefits of Leucine, make sure you consume it in proper dosage and as part of a complete whey protein blend like John’s Killer Protein®.



Targeting Inflammation and Downstream Protein Metabolism in Sarcopenia: A Brief Up-Dated Description of Concurrent Exercise and Leucine-Based Multimodal Intervention

Zhi Xia,1,2,† Jason Cholewa,3,† Yan Zhao,1,† Hua-Yu Shang,2,† Yue-Qin Yang,4,† Kassiana Araújo Pessôa,5,6Quan-Sheng Su,2 Fernanda Lima-Soares,5,6 and Nelo Eidy Zanchi5,6,*

Int J Sport Nutr Exerc Metab. 2018 May 14:1-26. doi: 10.1123/ijsnem.2018-0054. [Epub ahead of print]

Whey Protein Augments Leucinemia and Post-Exercise p70S6K1 Activity Compared to a Hydrolysed Collagen Blend When in Recovery From Training With Low Carbohydrate Availability.

Impey SG1Hammond KM1Naughton R1Langan-Evans C1Shepherd SO1Sharples AP1Cegielski J2Smith K2Jeromson S3Hamilton DL3Close GL1Morton JP1.

Differential effects of leucine and leucine-enriched whey protein on skeletal muscle protein synthesis in aged mice.Dijk FJ1van Dijk M2Walrand S3van Loon LJC4van Norren K5Luiking YC6.

Clin Nutr. 2017 Sep 23. pii: S0261-5614(17)31340-7. doi: 10.1016/j.clnu.2017.09.008. [Epub ahead of print]

Sports Med. 1999 Jun;27(6):347-58.

Leucine supplementation and intensive training.

Mero A1.

Effects of leucine-enriched essential amino acid and whey protein bolus dosing upon skeletal muscle protein synthesis at rest and after exercise in older women.

Wilkinson DJ1Bukhari SSI1Phillips BE1Limb MC1Cegielski J1Brook MS1Rankin D1Mitchell WK1Kobayashi H2Williams JP1Lund J1Greenhaff PL1Smith K1Atherton PJ3.


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