Leucine also increases physical endurance and strength, modulates

Leucine is a natural Branch Chain Amino Acid (BCAA) that is supplemented by our body in dietary form. With other two BCAAs – isoleucine and valine, Leucine makes up the one-third of muscles protein. It is very popular among athletes and gym-goers looking for visible muscle growth.

Besides this, it also increases physical endurance and strength, modulates insulin sensitivity, retains efficient energy levels and does much more. However, overconsumption of Leucine supplement does more harm than good.

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To get the most out of the BCAA, read further to know how Leucine works, what’re health benefits and the right Leucine dosage of Leucine along with safety measures.

Leucine Definition

There exist total 9 essential amino acids, and 3 branched-chain amino acids – isoleucine, valine, and Leucine. Enzymes in our liver don’t degrade BCAAs, and these amino acids easily enter the body’s tissues.

Among the three, Leucine is the most effective in muscular growth – the reason why it has garnered popularity in bodybuilding and gym circles. Leucine fulfills the nutrient need of muscles and stimulates skeletal muscle synthesis ten times better than other BCAAs.

Leucine is supplemented by consuming protein-rich foods such as egg white, lentils, meat, soya, etc. In fact, studies have purported that including this amino acid in diets of people who eat low-protein meals can promote their skeletal muscle growth.

Types of Leucine

Leucine can be classified as:


L-Leucine is the natural version of the BCAA and is found in the protein of the body. It is widely considered as the most important supplement in bodybuilding.


D-Leucine is created in the laboratory and is also used as a muscle-building leucine supplement.

Three primary functions of Leucine are:

·         Muscle growth

·         Modulating insulin sensitivity

·         Catabolic effect on fat

How Does Leucine Work?

Much of the Leucine benefits are attributable to its ability to stimulate muscle protein synthesis. Muscle Protein Synthesis (MPS) is the body’s switch to muscle development.

Protein is building a block of muscles. Protein synthesis is the process that breaks down nutrient and produces new proteins in our body. Muscle protein synthesis is the process that builds proteins in muscles and helps them grow. Facilitating greater muscle protein synthesis in the body helps it recover from exercise and fights the negative signs of aging.

Leucine plays a key role in facilitating muscle protein synthesis, hormone controlling and stabilizing blood glucose levels. More the protein synthesis, higher the skeleton muscle development.

Benefits of Leucine Supplement

Thousands of studies have proven Leucine benefits for bodybuilders. But the new exciting research shed light on some other important benefits of this health-promoting amino acid.  

Besides offering six-pack abs and attractive muscles, Leucine does much more for overall wellness of the human body. It supports our health in following ways:

Improves Energy Level

Breakdown of Leucine generates two energy-producing molecules – acetyl-CoA and acetoacetate. A rodent study revealed that Leucine acts as a precursor for different fats that later break down to produce energy. It increases insulin level in blood, leading to glucose uptake by the cells and ultimately, energy production.

Fasting increases Leucine levels in blood and stimulates enzymes to convert Leucine into ketone bodies and used for energy. So, Leucine helps maintain glucose levels and producing energy. 

 Words of caution: Leucine can decrease energy level.

Leucine blocks pyruvate, a molecule that glucose is converted to produce energy, breakdown, restricting the use of glucose for energy.

Advice: Bodybuilder should have a meal before workouts; otherwise, supplementation can hinder the workout.

Improves Muscles Growth

Workout leads to BCAA breakdown in all body organs, especially in muscles. BCAAs promote protein synthesis and prevent protein degradation, which further prevents muscle soreness and fatigue.

A DB-RCT study found that squat caused muscle fatigue and soreness. But those who consumed BCAA supplements had less soreness in the following days, while those who didn’t receive Leucine had prolonged soreness. 

Besides helping muscle recovery, Leucine also decreases muscle wasting in sick people. Another rodent study revealed that rats with cancer cachexia benefited increases muscle mass by 22% in the tibialis anterior and 23% in the gastrocnemius; thanks to Leucine!

Leucine also enhances total amino acid concentration in blood, which leads to more protein and developed muscles.

Boosts Protein

Higher concentrations of amino acids, especially with a high amount of Leucine, lead to greater effects on protein synthesis. Leucine solely can increase protein synthesis by 25%.

Leucine not only acts as an indispensable building block for muscle protein but is also crucial for regulating the production of proteins in our body.

Remember, protein is the building block of muscles. So, promoting protein synthesis is necessary to build muscles and decrease muscle waste.

Leucine individually can inhibit protein degradation that further decreased muscle wasting.

Maintains Nitrogen Balance

To recover faster after workout, a positive nitrogen balance is a must. Proteins are packed with nitrogen and induce a good nitrogen balance in our body. Since Leucine is the fourth highest source of protein, including it in your bodybuilding and workout meals can significantly contribute to fasten your muscle recovery process after an intense workout session.

Preserves Muscle Glycogen

During muscle strengthening exercises, Leucine levels drop significantly, leading to a reduction in glucose level as well. This is where Leucine supplements help!

The percentage of Leucine in protein supplements may vary between 5-10%. When you do an intense workout, Leucine supplement help prevents protein degradation and have a positive impact on replenishment of muscle glycogen stores.

Reduces the Risk of Arteries Hardening

Arteries hardening are linked to the high level of low-density lipoprotein (LDL). High – density lipoprotein reduces the risk of arteries hardening due to their participation in cholesterol transportation from the tissues to the liver.

The rodent studies showed that Leucine supplements decrease LDL by 41% and increase HDL by 40%.  It is also effective in decreasing atherosclerotic lesions by 58%. Leucine supplementation can also treat high cholesterol levels and chronic inflammation caused by atherosclerosis.

Helps with Weight Loss

In addition to anabolic effects on muscles, high Leucine diets can assist getting rid of obesity.  Studies have proved Leucine to be effective in helping weight loss. A diet rich in protein and low in carbohydrates is the safest way to shed few pounds from your body weight.

The benefit of Leucine for weight loss attributed to its capability to activate mTOR, which is a part of the brain called hypothalamus. When mTOR is activated, our body releases hormones that increase satiety. 

This appetite reducing effect is triggered by the production of dopamine, serotonin, and neurotransmitters.

Now, you may think Leucine reduces food intake and limits its role in augmenting MPS and reducing muscle atrophy. However, consumption of only 1.5 times greater dietary Leucine is required to boost protein turnover, and this amount doesn’t seem to affect good consumption.

Regulates Cholesterol and Blood Sugar

A 2009 study conducted by Medicine & Science in Sports & Science showed that Leucine might help properly regulate their cholesterol levels. This study was conducted on rats that received Leucine supplements and displayed raised blood levels of good cholesterol. 

Moreover, our body relies on glucose for energy. Though many amino acids supply glucose, only Leucine can substitute it entirely during fasting.

High glucose level may prevent a bodybuilder from using muscle for energy during an intense exercise. However, Leucine is more effective at assisting people to regulate their blood sugar than other two BCAAs. Both isoleucine and valine, convert to glucose at a slower rate than Leucine.

Taking Leucine – Dosage, and Safety

To leverage the bodybuilding benefit of Leucine, you must consume enough of this essential amino acid. Our body easily absorbs 100% of amino acids we consume. But, only a small percent of it goes to muscles. Besides muscles, amino acids are distributed to kidneys, liver, skin tissues, and cardiac. 

To consume the right amount of Leucine you consume to synthesis skeletal muscles, you need enough protein with a high Leucine content at one time.

According to one study, older adults must consume a higher concentration to reap Leucine’s benefits. Whereas, younger population have a more sensitive mTOR pathway and a lesser amount will work well.

The Refractory Period

When your body reaches the Leucine threshold, it must use the stored amino acid instead of using the more that enters the body. To achieve this threshold, make sure you eat a large amount of protein in a single meal and then replenish your body with protein after 4-5 hours, instead of having protein in small amounts throughout the day.

Leucine Dosage

The daily recommended Leucine dosage varies from 2 g to 5 g. Some studies recommend it to be as little as 2.5 g to drive protein synthesis. Many long-term studies suggest that people should take at least 8 g Leucine divided into meals throughout the day.

Note: Many studies have been conducted to gauge the right amount of Leucine, revealing a broad range of different results.

A good guideline suggests the daily Leucine intake between 2.5 g to 4.0 g per meal to maximize MPS. Less than 2 g of Leucine is used as calories and doesn’t contribute to protein synthesis. Think what you are planning to consume with your high Leucine protein or single Leucine supplement.

Understanding what the right amount of Leucine is can be confusing. Just choose a healthy diet with ample veggies, fruits, and sustainable proteins can help reach your Leucine threshold and maintain a healthy and muscular body.

The Best Leucine Sources

Our body doesn’t produce Leucine naturally. So, we have to intake Leucine by including protein-rich foods that are high in Leucine. But if you are a bodybuilder or want muscle growth, you must go for  Leucine supplements.

For improved results, you can incorporate some of the following Leucine-rich foods are:

Raw Parmesan Cheese

Besides being wholesome and delicious to boot, parmesan cheese is also the richest source of Leucine. It contains a whopping 121% of the recommended dietary intake of Leucine.

Grilled Beef

Grilled beef not only sounds crispy, but this meaty dish is also high in protein and Leucine. It boasts 116% of the suggested dietary intake of Leucine.

Roasted Soybean

Soybeans are the only vegetable in this list that features a rich amount of Leucine. Roasted soybean contains about 118% of Leucine recommended as dietary intake.

Cooked Tuna

Tuna lists among the best-canned fishes in the world. The fresh, cooked Tuna boasts 84% of the daily recommended dietary intake of Leucine.

Cooked Chicken Breast

Freshly cooked chicken breast makes a quite healthy dish and is a rich source of 75% of daily recommended Leucine.

Cooked Pork

The heart-healthy pork contains around 94% of the daily recommended dietary intake of Leucine amino acid.

Pumpkin Seeds

Pumpkin seeds contain 87% of daily recommended dietary intake, which makes it a great source of this amino acid.


Peanuts contain 66% of the recommended dietary intake of leucine.

White Beans

White beans contain 22% of the recommended dietary intake of Leucine.

Besides these, other rich sources of Leucine are white beans, peanuts, cooked octopus, and legumes.     

Best Time To Take Leucine


Consume 2.5 g Leucine 30 minutes before training to encourage muscle building stimulus. Leucine activates mTOR pathway, induce protein synthesis and promotes re-growth of new muscle tissue.

Intra Workout

Add 5 g Leucine powder to your shake for intra workout to avoid muscle soreness following the intense workout.

Post Workout

Mix 5 g Leucine in your post-workout protein shakes to create a rich combination of carbohydrates, protein, and Leucine to boost muscle protein synthesis.

Before Bed

Take 5 g Leucine before bed to boost muscle building hormone production and accelerate muscle recovery while sleeping.

Between Meals

Additional 1.2 g to 2.5 g Leucine can be consumed with/between meals to encourage protein synthesis and fasten the recovery process. Add the amino acid to a low-carb diet to prevent muscle breakdown and maintain energy level.

Understanding Leucine Side Effects

An inappropriate amount of Leucine may cause low blood sugar level if the amino acid doesn’t convert into sugar.

Leucine overdose may increase blood ammonia levels, causing live damage.

Serotonin exists in blood cells that contracts the blood vessels and transmit signals to the brain. Leucine, being a fast-absorbing supplement, competes with the absorption of other elements that are serotonin precursors.

To avoid these Leucine side effects, opt for food diet or consult with your trainer to discuss the right daily recommended Leucine amount.

However, research is going on to formulate supplements with Leucine ingredients that have no side-effect at all. And, the best benefits of Leucine can be achieved by taking it in the proper amount and incorporating regular workout.