If you're looking to build muscle, you'll want to get familiar with leucine — especially if you're on a plant-based, vegetarian or vegan diet.
Leucine is a powerful essential amino acid known for building muscle and burning fat. If your goal is to get lean, try adding more leucine foods to your diet.
What Is Leucine?
Protein is made up of amino acids and each source of protein has a unique amino acid profile. Some protein sources are high in the branched-chain amino acids (BCAAs) leucine, isoleucine and valine, while other sources of protein are higher in amino acids such as arginine and L-glutamine.
Every amino acid plays a different role in the body, primarily related to making enzymes.
The amino acid leucine gets a lot of attention as it can improve body composition and physical performance in both recreational and elite athletes. It's also proven to be a valuable nutrient in rebuilding muscle in older adults with sarcopenia (age-related muscle loss) and musculoskeletal injuries (injuries or pain in the joints, ligaments, muscles, nerves, tendons and structure that support the limbs, back and neck).
As is the case with all essential amino acids, leucine cannot be produced by the body and must be obtained from food. While leucine is present in some plant-based foods (more on that below), it is generally higher in quantity and easier to find in food sourced from animals. That's why plant-based diet followers looking to gain muscle and lose fat should pay extra attention to their leucine intake.
How Leucine Helps You Gain Muscle and Lose Fat
Research shows that leucine plays a role in both muscle protein synthesis and fat burning.
In a September 2016 Journal of Strength & Conditioning Research study, people who ate 3 grams of beta-hydroxy beta methyl butyrate (a form of leucine) daily for 12 weeks found they could work out for longer before fatiguing as well as noticed increases in muscle mass and decreases in fat mass.
Another study published in 2009 in Medicine and Science in Sports and Exercise found similar results in 17 recreational active, college-aged males with the same supplement protocol and timeline. These participants also experienced statistically significant increases in muscle power and muscle strength.
While these results are promising, there are other studies published that did not find leucine to have a significant effect on body composition or physical performance among healthy young people.
Yes, research on leucine's effect on body composition in healthy young and middle-aged adults is mixed, but there are more consistently positive findings in research among older adults.
For example, leucine supplementation showed beneficial effects on body weight, body mass index and muscle mass in older people prone to sarcopenia, per an April 2015 meta-analysis in the Journal of Nutrition, Health, and Aging.
Research also consistently supports leucine's role in recovery from injury. People recovering from musculoskeletal injuries such as broken bones, pulled or severed tendons or torn muscles benefit from leucine's effects on rebuilding muscle and bone collagen.
How to Get More Leucine in Your Diet
Leucine is most commonly found in animal foods such as beef, poultry, fish, cheese, eggs and milk, but it's also present in plant-based foods in smaller amounts.
Men on a vegan diet had statistically significant lower levels of leucine in their blood, while vegetarians had similar (but still lower) levels of leucine compared to meat-eaters, per a September 2016 study in the European Journal of Clinical Nutrition. The researchers suggest that the leucine found in the vegetarians' bloodstreams was likely from milk products, which are high in leucine.
If you're on a vegetarian or vegan diet, try getting most of your protein from plant-based sources and regularly eat soybeans and soy-based products as well as beans and legumes to obtain all of the essential amino acids including leucine, the Academy of Nutrition and Dietetics recommends.
The recommended daily intake (RDI) for leucine is 17.7 milligrams per pound of body weight. Note that the RDI percentage in the table below is calculated for someone weighing 154 pounds.
Top Vegan Leucine Foods
Milligrams of Leucine and RDI
1 cup firm tofu
3,508 mg, 128% RDI
1 cup cooked navy beans
1,674 mg, 61% RDI
1 oz. squash and pumpkin seeds
678 mg, 25% RDI
1 oz. hemp seeds
614 mg, 23% RDI
1 oz. roasted pistachios
476 mg, 17% RDI
1 oz. roasted peanuts
436 mg, 16% RDI
1 oz. raw cashews
418 mg, 15% RDI
1 oz. chia seeds
389 mg, 14% RDI
If you're looking to simultaneously gain muscle and lose fat, leucine is an important nutrient to pay attention to. It could be the difference between you stepping off your plateau and seeing results.
If you are primarily or exclusively eating a plant-based diet, make sure to incorporate those that contain sources of leucine, including soy, beans and seeds into your daily diet.
3 Leucine-Rich Plant-Based Recipes
1. Bulgur and Black Beans
Black beans are rich in leucine and combining them with a grain like bulgur rounds out the amino acids available in the meal. Together, beans and grains provide a wider variety of amino acids than if you enjoyed each on its own. This recipe is great when paired with a salad or another veggie side for a balanced meal.
Get the Bulgur and Black Beans recipe and nutrition info here.
2. Chef's Tofu Salad
This salad can be tossed together in a matter of minutes and includes not one but two plant-based foods rich in leucine. Tofu is one of the richest vegan sources of leucine and kidney beans don't fall far behind.
Get the Chef's Tofu Salad recipe and nutrition info here.
3. Edamame Trail Mix
Snacking on dry-roasted edamame is an easy way to boost your leucine intake. The protein and leucine in the edamame and carbohydrates in the cranberries make this a well-rounded post-workout nosh.
Get the Edamame Trail Mix recipe and nutrition info here.
- Medicine & Science in Sports & Exercise: "Effects of Amino Acids Supplement on Physiological Adaptations to Resistance Training"
- The Journal of Nutrition, Health & Aging: "Effects of Leucine-Rich Protein Supplements on Anthropometric Parameter and Muscle Strength in the Elderly: a Systematic Review and Meta-Analysis"
- Journal of Strength and Conditioning Research: "The Effect of β-Hydroxy-β-Methylbutyrate on Aerobic Capacity and Body Composition in Trained Athletes"
- USDA: "Top 10 Foods Highest in Leucine"
- The University of Lisbon Repository: "The Effects of Leucine Metabolites on Performance, Body Composition and Biochemical Markers of Muscle Damage and Inflammation"
- Amino Acids: "The Role of Leucine and its Metabolites in Protein and Energy Metabolism"
- Annals of Nutrition and Metabolism: "Nutrition for Acute Exercise-Induced Injuries"
- Journal of American Dietetic Association: "Position of the American Dietetic Association: vegetarian diets"