The Mighty Leucine: Unlocking the Surprising Health Benefits


Leucine was first obtained from cheese in 1819, by the French chemist, Proust. In 1820, Braconnot used acid hydrolysis to isolate leucine from skeletal muscle and wool and gave the substance its name. Its structure wasn’t identified until 1891 when Schulze synthesized leucine.
Leucine is the most abundant branched-chain amino acid (BCAA) found in animal and plant proteins. It plays an important role in protein synthesis and metabolic function and is sometimes used as a dietary supplement or flavor enhancer.

Original By Ben Mills – Own work, Public Domain.

Leucine Health Benefits

One of the primary functions of leucine is as a building block for protein synthesis. It helps to activate a signaling pathway responsible for initiating protein synthesis in cells. This makes it important for the growth and repair of muscles, as well as other tissues in the body that contain protein.
Leucine also plays a role in regulating blood sugar levels by stimulating the production of insulin, a hormone that helps to lower blood sugar. It has also been found to play a role in the modulation of the immune system.
Additionally, Leucine has been suggested to have a beneficial effect on bone density and help prevent bone loss, this is being researched. It also appears to be able to potentially help with weight loss by reducing muscle wasting, a process called catabolism.
Leucine supplements are used in sports nutrition as it can promote muscle protein synthesis and reduce muscle damage following exercise, this is why it is a commonly used supplement by bodybuilders and athletes.

Original By Ben Mills – Own work, Public Domain.

Foods rich in Leucine

Leucine is found in high concentrations in foods that are rich in protein, such as:
  • Meat: Beef, pork, poultry, and other meats are all high in leucine.
  • Fish: Fish such as tuna, salmon, and cod are also good sources of leucine.
  • Dairy products: Milk, cheese, and yogurt are all high in leucine.
  • Soy products: Tofu and soy milk are good vegetarian sources of leucine.
  • Eggs: Eggs are also a good source of leucine.
  • Legumes: Beans and lentils are also good sources of leucine.
  • Nuts and seeds: Almonds, cashews, and pumpkin seeds are good sources of leucine.
  • Rice and bread: Whole grain bread and brown rice are also good sources of leucine.
It is important to note that leucine is an essential amino acid, and as such, it is important to consume a varied and balanced diet that includes a variety of protein-rich foods to ensure that you are getting enough leucine.

Recommended daily intake

The recommended daily intake of leucine can vary depending on factors such as age, sex, and level of physical activity.
Age, gender, life stage group
  Leucine RDA (mg/kg/day)
0–6 month
7–12 month
1–3 years
4–8 years
9–13 years
14–18 years
9–13 years
14–18 years
Adult Men and Women
19 and older
Pregnant Women
All ages
Lactating Women
All ages

Leucine deficiency

A deficiency of leucine is relatively rare, as it is found in a wide variety of foods. However, certain groups of people may be at risk of a leucine deficiency, including:
  • People with malabsorption disorders: Individuals with conditions that affect the ability to absorb nutrients from food, such as celiac disease or Crohn’s disease, may be at risk of a leucine deficiency.
  • People on a low-protein diet: Those who consume very low amounts of protein in their diet may not be getting enough leucine.
  • People with certain genetic disorders: Some genetic disorders, such as Maple Syrup Urine Disease can increase the risk of leucine deficiency
A deficiency in leucine can lead to a loss of muscle mass, reduced growth and wound healing, skin problems, a weakened immune system, and many other health problems. A severe deficiency of leucine can cause a rare genetic disorder called Maple Syrup Urine Disease (MSUD). which can be life-threatening if left untreated.
If you think you may be at risk of a leucine deficiency, it is important to speak with a healthcare professional, who can help you determine if you need to make changes to your diet or take a supplement to increase your leucine intake.

Leucine excess

Consuming large amounts of leucine, especially from supplements, can have negative side effects. It is known that high levels of leucine can cause:
  • Digestive upset: Stomach discomfort, nausea, and diarrhea.
  • Liver and Kidney problems: High levels of leucine in the blood can be hard on the liver and kidneys. The long-term effects of consuming high levels of leucine on these organs are not well understood, but it is known that they can cause damage and can make existing liver or kidney disease worse.
  • Pellagra: Pellagra is a vitamin deficiency disease that typically results from a niacin deficiency, although high levels of leucine may also cause it to occur. Pellagra can make people highly sensitive to sunlight and can have many other detrimental effects. According to a 1978 study published in “The American Journal of Clinical Nutrition,” excess leucine causes an amino acid imbalance in the body that can lead to the onset of pellagra.
  • Low blood sugar: Leucine can reduce blood glucose levels due to its ability to stimulate insulin production by the pancreas. Consuming large amounts of leucine may cause a drop in blood sugar levels, leading to feelings of dizziness or weakness.
It’s important to note that taking high doses of leucine supplements, especially in the absence of other essential amino acids, can be harmful. It is recommended to consume it in moderate amounts as part of a balanced diet. If you are considering taking leucine supplements, it’s important to talk to a healthcare professional first to determine the appropriate dosage for you.
Additionally, People with liver or kidney disease, pregnant or breastfeeding women, and children should avoid high doses of leucine supplements, it’s also important to note that consuming more leucine doesn’t mean that more protein synthesis will occur, this is because there are other limiting factors that affect protein syntheses like energy and other amino acids.

Fun facts

Here are a few fun facts about leucine:
  • Leucine is named after the Greek word “leukos,” which means “white.” This is because leucine crystals are white in color.
  • Leucine is one of the three branched-chain amino acids (BCAAs) that are particularly important for muscle growth and repair. The other two are isoleucine and valine.
  • Leucine has been found to play a role in the regulation of blood sugar levels by stimulating the production of insulin, a hormone that helps to lower blood sugar.
  • Leucine is used in wound healing and some skin care products.

Why is Leucine important for sports performance?

Leucine is important for sports performance for several reasons:
  • Muscle growth and repair: As an essential amino acid, leucine is necessary for protein synthesis, the process by which cells use amino acids to build new proteins. This makes it important for the growth and repair of muscle tissue, which is essential for athletes who need to build and maintain muscle mass.
  • Activating protein synthesis: Leucine is a key player in activating a signaling pathway called mTOR, which is responsible for initiating protein synthesis in cells. This makes leucine a crucial amino acid for muscle recovery and growth, especially after high-intensity training and endurance activities.
  • Reducing muscle damage: Leucine has been shown to reduce muscle damage following exercise by promoting muscle protein synthesis and decreasing muscle protein breakdown. This can lead to faster recovery and better overall performance.
  • Improving endurance: Studies have shown that consuming leucine before endurance exercise can help to preserve muscle mass and improve endurance. This is probably due to the ability of leucine to activate protein synthesis and promote muscle recovery.
  • Enhancing muscle hypertrophy: Leucine is considered to be one of the most anabolic amino acids, which means it promotes muscle growth. Consuming adequate amounts of leucine may enhance muscle hypertrophy and increase muscle mass, which is beneficial for athletes looking to build muscle size and strength.

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