Learn all about leucine, the essential amino acid for muscle building!
Among the amino acids, leucine is likely the most important for muscle building, as this essential amino acid plays a central role in protein synthesis and the growth of our skeletal muscles. But what exactly is the effect of leucine, which foods are rich in it, how does it work, and should you supplement with it? These are the questions we’ll answer in today’s article!
What is Leucine?
All proteins are composed of amino acids, small molecules that play a vital role in nearly every biological process in our bodies. There are 20 different proteinogenic amino acids in total, nine of which are classified as "essential." Essential amino acids cannot be produced by our bodies and must therefore be obtained through our diet. Among these crucial amino acids are the branched-chain amino acids (BCAAs) valine, leucine, and isoleucine. All three are important for muscle growth and recovery after exercise [1].
Leucine, however, holds a special place because it directly influences the mTOR signaling pathway. This is a central mechanism in our body that regulates cell growth and protein synthesis. Simply put, leucine activates this mechanism, which in turn stimulates muscle protein synthesis. This makes leucine one of the most important amino acids for building and maintaining muscle mass [2]. Additionally, leucine promotes insulin secretion [3], which helps provide the body with the necessary nutrients for protein synthesis.
Foods High in Leucine
There are many foods that are good sources of leucine. Animal products, such as meat and poultry, contain the highest amounts of leucine per gram. Chicken, beef, and pork contain about 1.7 to 2.5 grams of leucine per 100 grams. Seafood and fish, such as shrimp, tuna, and salmon, also have high amounts.
Dairy products like cheese and yogurt can also provide solid amounts of leucine. A glass of milk, for example, contains about 0.8 grams of leucine. Cheese and yogurt vary slightly depending on the type, but often contain between 1 and 1.5 grams per 100 grams.
On the plant-based side, foods like soy, lentils, chickpeas, and quinoa are also sources of leucine, although they contain slightly less compared to animal products. Soy provides about 1.2 grams of leucine per 100 grams, while chickpeas and lentils contain around 0.7 to 0.8 grams. Quinoa, a popular plant-based protein and carbohydrate source, offers about 0.7 grams per 100 grams. It’s worth noting that we often consume larger quantities of these plant-based sources, which helps offset the lower leucine content [4].
Moreover, it’s important to consider the greater sustainability of plant-based foods. Soy and lentils, for example, produce significantly fewer greenhouse gas emissions and use less water and land compared to meat production. So, by covering your protein and leucine needs at least partially with plant-based sources, you’re doing something good not only for your health but also for the environment [5].
Leucine as a Supplement
If you’re wondering whether leucine is available in isolated form as a supplement, the answer is yes! You can purchase leucine in both powder and capsule form. However, it’s usually not necessary—or even beneficial—to supplement with this amino acid alone, as it can be better utilized by the body when combined with a complete protein source. Isolated leucine also has a somewhat bitter taste and can easily ruin smoothies and shakes if you use too much. An ideal amount of leucine for muscle building is 2-5 grams per meal, particularly in combination with protein.
Combining Leucine with Other Nutrients
Leucine can achieve its full potential, particularly when combined with carbohydrates and proteins. This combination also promotes insulin secretion, which enhances the uptake of amino acids into the muscles. After your workout, a shake with protein powder, leucine, and a carbohydrate-rich banana is an excellent choice to kickstart optimal recovery!
Make sure to integrate enough leucine into your diet by considering the following tips:
- Consume a leucine-rich snack before and after your workout to prevent muscle breakdown and activate muscle protein synthesis.
- Ensure that all your main meals contain a protein source (and therefore leucine). If you follow a plant-based diet, also make sure that the portion size is sufficient.
- Make sure that the protein powder you use contains at least 2.5 grams of leucine per serving.
Remember that a balanced diet is the foundation of your overall health, even as you focus on protein and leucine. Ensure that you’re also getting enough carbohydrates and healthy fats. If you’re unsure about selecting the right foods or creating a nutrition plan, consult with a nutritionist!
Leucine in WAM Protein
To ensure you don’t miss out on leucine, even with the lower leucine content in plant-based proteins, we’ve fortified our vegan WAM Protein with isolated leucine. With every serving of WAM Protein, you’re ensuring an adequate amount of 2.5 grams of the BCAA Leucine in combination with high-quality plant-based proteins. We’ve placed special emphasis on flavor development in our protein powder and deliberately avoided artificial sweeteners like sucralose. This way, you not only get enough leucine, but you can also enjoy a shake with a natural, not-too-sweet taste. Instead of sunflower oil, modified starch, and xanthan gum, we rely on coconut milk and guar gum in our powder for outstanding, pleasant creaminess and better digestibility.
The Effect of Leucine on Muscle Building
As we already know, leucine promotes muscle protein synthesis by stimulating the mTOR signaling pathway, which in turn triggers the production of new cells in the body. This is particularly relevant for those who train intensively and want to shorten their recovery times while repairing and strengthening their muscles more quickly. However, a high intake of leucine through food is also crucial for those who do not train at all or only minimally, as it helps prevent muscle breakdown. This is especially important for the elderly, who are often affected by age-related muscle loss (sarcopenia) [6]. But it can also be relevant for younger people, such as during injury- or illness-related training breaks.
Leucine Side Effects
Even with such an important amino acid like leucine, you should avoid overdosing. We’re talking about taking over 30 grams per day or 500 mg per kg of body weight per day [7]. This is another reason why it’s more sensible to consume leucine as part of a protein powder or as food in combination with carbohydrates and proteins rather than as an isolated supplement. Possible side effects of too much leucine include stomach discomfort, nausea, and headaches [8]. If you still choose to take isolated leucine, make sure not to exceed the recommended dosage and account for leucine from other foods.
Final Thoughts on Leucine Intake
Leucine is one of the most important amino acids for muscle building and should be included in every nutrition plan. Ensuring an adequate intake of this amino acid through your diet is relatively easy if you choose the right foods. Protein shakes can make it even easier, especially if, like our WAM Protein, they’re fortified with a little extra leucine. We hope our article helps you get the most out of your training and nutrition.
If you have any more questions about leucine or specific nutrition topics, just send us an email. We look forward to hearing from you!
Sources
[1] Plotkin DL, Delcastillo K, Van Every DW, Tipton KD, Aragon AA, Schoenfeld BJ. Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review. Int J Sport Nutr Exerc Metab. 2021 May 1;31(3):292-301.
[2] Wilkinson K, Koscien CP, Monteyne AJ, Wall BT, Stephens FB. Association of postprandial postexercise muscle protein synthesis rates with dietary leucine: A systematic review. Physiol Rep. 2023 Aug;11(15):e15775.
[3] Kalogeropoulou D, Lafave L, Schweim K, Gannon MC, Nuttall FQ. Leucine, when ingested with glucose, synergistically stimulates insulin secretion and lowers blood glucose. Metabolism. 2008 Dec;57(12):1747-52.
[4] Mariotti F, Gardner CD. Dietary Protein and Amino Acids in Vegetarian Diets-A Review. Nutrients. 2019 Nov 4;11(11):2661.
[5] Lynch H, Johnston C, Wharton C. Plant-Based Diets: Considerations for Environmental Impact, Protein Quality, and Exercise Performance. Nutrients. 2018 Dec 1;10(12):1841.
[6] Lin CC, Shih MH, Chen CD, Yeh SL. Effects of adequate dietary protein with whey protein, leucine, and vitamin D supplementation on sarcopenia in older adults: An open-label, parallel-group study. Clin Nutr. 2021 Mar;40(3):1323-1329.
[7] Rasmussen B, Gilbert E, Turki A, Madden K, Elango R. Determination of the safety of leucine supplementation in healthy elderly men. Amino Acids. 2016 Jul;48(7):1707-16.
[8] Martínez-Arnau FM, Fonfría-Vivas R, Cauli O. Beneficial Effects of Leucine Supplementation on Criteria for Sarcopenia: A Systematic Review. Nutrients. 2019 Oct 17;11(10):2504.
