Uses of leucine
Although further research is needed, people commonly use leucine supplements to build muscle mass and improve athletic performance.
muscle health
Studies have looked at leucine's role in supporting muscle growth and recovery, with mixed results.
muscle growth
Leucine is popular among bodybuilders for its potential to support muscle growth. Branched-chain amino acids, especially leucine, have been shown to activate the mTOR signaling pathway, thereby promoting muscle growth.
However, the evidence is mixed. When combined with strength training, leucine appears to provide the greatest health benefits for older adults, especially those with age-related muscle loss (sarcopenia).
For example, a 2022 randomized controlled trial examined the effects of leucine supplementation on body composition and body function in healthy Korean adults aged 50 years and older. All participants completed 12 weeks of strength training with or without leucine supplementation.
At the end of the study, the group that combined leucine supplementation with strength training had significant improvements in lean muscle mass compared to those who only strength trained.
However, a recent review of 17 randomized controlled trials found no improvements in lean muscle mass and strength in older adults who took isolated leucine supplements without strength training.
Similarly, another small randomized controlled trial found that high-dose leucine supplementation did not improve muscle mass or strength in resistance-trained men who consumed adequate dietary protein.
muscle recovery
According to research, leucine supplementation combined with resistance training may help improve muscle recovery. It appears to be most beneficial when combined with other essential amino acids.
A recent study found that the essential amino acid rich in leucine can help reduce muscle damage days after strenuous resistance exercise. However, no significant improvements in muscle protein synthesis were observed during the study.
Another study examined the effects of leucine supplementation on muscle recovery after resistance exercise in young adults but found no significant improvements.
Can reduce inflammation
While inflammation is a normal part of the body's healing process, chronic inflammation may play a role in the development of many diseases, including heart disease, autoimmune diseases, cancer, and diabetes.
A study of teens and young adults with cerebral palsy found that participants who took leucine supplements for 10 weeks had significant improvements in inflammatory markers. Improvements in muscle strength, muscle soreness, mood, muscle mass, and overall health were also observed.
However, the study was small, including only 21 participants.
Can stabilize blood sugar
Human and animal studies suggest that supplementing leucine, especially along with glucose (sugar), may help stimulate insulin secretion, which can help control blood sugar.
Additionally, a 2014 test-tube study noted that leucine can help control blood sugar levels by helping to improve insulin sensitivity and promote glucose uptake.
What are the side effects of leucine?
Side effects are less likely to occur from consuming foods rich in leucine. However, there may be potential side effects from consuming leucine supplements.
However, further human studies are needed to confirm these effects.
Common side effects
No serious side effects have been reported when taking leucine supplements at recommended doses. However, taking high doses of leucine supplements may cause some side effects, including:
- Gastrointestinal (GI) Issues: Some users report gas, nausea, and diarrhea when combined with high doses of whey protein.
- Imbalances of other amino acids, including valine and isoleucine: This may have a short-term positive effect on muscle protein synthesis, but not long-term muscle growth.
- Hypoglycemia: High doses of leucine may cause blood sugar to drop too low.
serious side effects
High doses of leucine may interfere with the production of niacin from tryptophan, thereby worsening the symptoms of pellagra (a disease caused by a deficiency of niacin or tryptophan).
Precaution
People with the following health conditions should be aware of possible safety issues when taking leucine supplements:
- Diabetes: Because leucine may cause hypoglycemia, people with diabetes who take medications to control their blood sugar may be at greater risk of developing hypoglycemia.
- Maple syrup urine disease (MSUD): People with MSUD are unable to break down branched-chain amino acids such as leucine, causing them to build up in the blood. This may cause neurological symptoms including drowsiness and irritability.
- Pregnancy and Breastfeeding: Due to a lack of research, people who are pregnant or breastfeeding should avoid leucine supplements unless otherwise advised by a healthcare provider.
- Children: Single amino acids may cause growth problems in children and should be avoided.
Research shows that doses above 500 milligrams (mg) per kilogram (kg) of body weight per day increase ammonia in the blood. This can lead to elevated ammonia levels in the brain, leading to neurological damage and confusion.
However, one study noted that blood ammonia levels returned to normal the day after stopping taking the supplement, without serious health consequences.
If you develop confusion, severe gastrointestinal discomfort, or other serious symptoms, stop taking leucine and contact your healthcare provider.
Dosage: How much leucine should I take?
There are no official dosage guidelines for leucine supplements. However, a common dose is 5 grams (g) per day.
According to the World Health Organization (WHO), healthy adults should consume an average of 39 mg/kg of leucine per day.
This means that a 176-pound (80-kilogram) person needs approximately 3.1 grams of dietary leucine per day.
However, research shows that older adults may need twice as much as current recommendations. 20 For example, older adults are typically recommended to consume 3 grams of leucine and 25 to 30 grams of protein at three main meals to prevent or recover from muscle loss.
What happens if I take too much leucine?
There is little information on leucine overdose and toxicity in humans. However, to prevent toxicity and serious side effects, be careful with proper dosage and keep the upper limit in mind.
According to recent research, daily leucine intake for adults should be limited to less than 500 mg/kg, or about 35 grams for a person weighing 154 pounds (70 kg).
As mentioned previously, doses above 500 mg/kg can cause elevated ammonia concentrations in the brain.
If you experience severe gastrointestinal discomfort or confusion, you may have taken an overdose and should seek medical attention immediately.
interactive
Use caution when taking leucine with:
- Diabetes medications: Leucine may lower blood sugar. May cause dangerously low blood sugar levels when used with insulin or other diabetes medications.
- Niacin (B3) and Vitamin B6: Leucine interferes with the production of niacin and vitamin B6.
- Erectile dysfunction drugs: Animal studies suggest that leucine may enhance the effects of PDE5 inhibitors, such as Viagra (sildenafil).
- Parkinson's disease medications: Leucine may interfere with the absorption of levodopa, making it less effective.
How to store leucine
Storage instructions may vary depending on the supplement brand. Read product labels carefully to make sure supplements are stored correctly.
In general, dietary supplements should be stored in their original packaging in a cool, dry place. They should be kept out of the reach of children or pets, preferably in a locked cabinet.
Supplements should be discarded after one year or as directed on the product label. If you have any questions about how to dispose of supplements or medications, ask your healthcare provider or pharmacist.
Similar supplements
Leucine can be used to reduce inflammation, regulate blood sugar, and support muscle health.
Other supplements with similar properties include:
- Creatine: Creatine supplements have been shown to improve athletic performance and lean body mass during training. It may also help prevent age-related muscle and bone loss in older adults.
- L-Carnitine: An amino acid commonly used to enhance athletic performance.
- Whey protein: Whey protein is quite high in leucine, which may help prevent muscle loss in older adults. For best results, it should be used in conjunction with resistance training.
