Leucine – Health Benefits and Side Effects

Leucine – Health Benefits and Side Effects:

It is an essential amino acid that was discovered in 1819. Its chemical structure was discovered only in the late 19th century and is part of the three branched amino acids (valine, isoleucine, and leucine).

They are vital to the human body and are needed for us to survive.

Its chemical formula is HO2CCH(NH2)CH2CH(CH3)2. In 1891, the structure of this amino acid was established by laboratory synthesis.

It is used mainly by the liver, adipose, and muscle tissue. It is present in hemoglobin in relatively large amounts (~ 15%). It can not be made by the body, hence, it must be acquired through dietary supplements or food.


This amino acid operates on the skeletal muscle level by two anabolic effects, namely: stimulation of protein synthesis and inhibition of protein lysis.

It interacts with protein synthesis and insulin signaling pathways, in order to maintain muscle proteins during the energy restriction period.

Studies show that this essential amino acid stimulates protein synthesis, without the need for plasma insulin concentration; however, insulin doesn’t have the same effect without it.

A high dose of carbohydrates (glucose and sucrose), which leads to an increased insulin level of over 2.5 times higher than normal, didn’t affect protein synthesis.

Health Benefits

Promotes A Healthy Growth

It is necessary for the optimal growth of children and the maintenance of nitrogen balance in adults.

Weight Loss

Obesity and overweight and are now a global epidemic, with more than 1 in 5 people qualifying as obese worldwide.

According to a study published in the Journal of the Endocrine Society, children with obesity face a 400 percent increased risk of developing type 2 diabetes Mellitus compared to children with a body mass index in the normal range, However, according to some studies, increasing dietary leucine may help control obesity.

Good For Diabetics

It is important for the synthesis of proteins and in many metabolic functions. It helps adjust blood sugar levels, growth, and repair of muscle and bone tissues, production of growth hormone, and healing of wounds.

It also prevents the decomposition of muscle proteins after trauma or severe stress and can be beneficial for people with phenylketonuria.


The deficiency of this amino acid is rare. Symptoms include – dizziness, headaches, depression, fatigue, irritability, loss of balance, or confusion. In addition, maple syrup urine disease results from deficient activity of the branched-chain amino acids.


The recommended daily dose isn’t officially established yet, but most suggest that it should be approx. 26 mg/kg body weight for adults. The best way to consume this essential amino acid is to add it before physical exercise in the form of BCAAs.

As an interesting fact, if you suffer from a deficiency of this amino acid, your physical body will not be able to make use of the protein which you give it – no matter how much protein you ingest.

Food Sources

It is found in red kidney beans, chickpeas, navy beans, lentils, beans, soybeans, sunflower seeds, chia seeds, pumpkin seeds, sesame seeds, watermelon seeds, Brazil nuts, flaxseeds, peanuts, almonds, cashew nuts, hemp seeds, pistachios, hazelnuts, brown rice, asparagus, spirulina, meat, dairy products, eggs, fish, oat bran, millet, oatmeal.

Side Effects of Leucine

Intravenous administration of this amino acid has been shown to cause severe hyperglycemic reactions and insulin resistance, especially when taking diabetes medication. In some cases, it can lead to pellagra which occurs when the body lacks an adequate amount of vitamin B3.

Supplementation with this amino acid can also lead to ammonia accumulation that can lead to kidney and liver failure if not addressed. Always take a healthcare specialist’s opinion before you start using this supplement.

Therefore, individuals with impaired kidney or liver function should not take this amino acid without first consulting a healthcare specialist, as large doses of BCAAs may aggravate these conditions.


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