THE EXERCISE BENEFITS OF LEUCINE

You’ve just finished the final set of your workout. You’re thirsty, tired, and ready for recovery. And while there are plenty of options when it comes to post-workout supplements, you know you want something that can fuel your skeletal muscles without weighing you down.

Have you considered leucine? It could be the perfect complement to your next leg day or 5K run. Leucine is found in food, but it’s also a popular supplement for athletes, weightlifters, and others who just want to be proactive when it comes to wellness. One 2020 study even explored how Leucine can be a great resource for the elderly, helping to combat the loss of muscle mass in old age.

WHAT IS LEUCINE?

As you may remember from biology class, there are 20 amino acids used by the body to create protein and perform other crucial tasks. Leucine is one of nine essential amino acids that cannot be created in the body and must therefore be consumed in the food you eat. It is also one of the three branched-chain-amino-acids (BCAAs) that are necessary for life and make up about 35% of your body’s muscle protein. For this reason, BCAAs are a common ingredient in pre-workout supplements. The three BCAAs are leucine, isoleucine, and valine, and they help preserve the body’s glycogen, which fuels your muscles and helps to limit the breakdown of  muscle protein for energy during intense exercise. This helps preserve your muscles and allows for the activation of muscle protein synthesis. BCAAs are also metabolized in skeletal muscle, unlike other amino acids that are oxidized in the liver.

Leucine seems to be the most important BCAA for enhancing muscle protein recovery after you work out. It acts as a signal molecule, regulating the homeostasis of proteins in the body. Leucine helps to limit muscle protein break down and helps encourage protein creation. All of this helps maintain muscle mass, which is important for those trying to get stronger and look more muscular.

WHAT DOES LEUCINE DO?

Leucine can fuel the repair of your skeletal muscles after you exercise.2 It helps support muscle protein balance. It also influences anabolic and catabolic signaling compounds within the body, which leads to increased protein synthesis. In a meta-analysis examining the elderly, patients supplementing with leucine had an increase in the proteins needed to build muscle and had less muscle breakdown.3 This breakdown is what happens after muscles get slightly damaged in a workout before being rebuilt and is partially responsible for the feeling of soreness you get after a new or especially intense workout.

Leucine also supports muscle protein synthesis during the aging process, which for some can be manifested as soon age 30. To counteract this natural loss of muscle, it is important to continue strength training, while also ensuring you’re consuming enough protein. The previously-mentioned meta-analysis of the elderly showed that older adults who supplemented with leucine gained body weight, increased their BMI, and increased their lean body mass, all of which can be helpful through the aging process.

Leucine is one of the BCAAs that acts as a nutrient regulator of insulin biosynthesis and secretion. Insulin release helps reduce muscle protein breakdown. Muscle protein breakdown occurs after intense training, but to build muscle, you need to slow down or stop this process. This process of protein synthesis is especially hard to combat after age 40. So, while leucine can be helpful for any athlete, it can be even more beneficial in older adults.

FOOD SOURCES OF LEUCINE

Leucine can be found in a wide variety of foods. It occurs naturally in plant and animal proteins such as dairy products, fish, soy, meat, poultry, beans, and eggs.5 It can also be found in protein powders made from complete proteins such as whey, including native whey protein, which has more leucine than other types of whey. In fact, with about 10% leucine content (or about 2.5g per 25g scoop), whey protein powder offers more BCAAs than most other protein powders. To compare, soy offers about 6% BCAAs and casein offers about 8%.

If you’re not into supplements, you can find lower doses of leucine in a multitude of foods you can eat for breakfast, lunch, dinner, or as a snack. Some of the foods with the highest leucine count include ham, steak, and chicken breast. If you don’t eat meat, you can find high amounts of the protein in asiago and ricotta cheese, as well as partially skimmed cow’s milk and Greek yogurt. Pescatarians can find leucine in anchovies, clams, and cod, amongst several other fish, while vegans can get their share of leucine in beans, chickpeas, and lentils. Leucine can also be found in bread, corn, dried fruit, cashews, and hazelnuts.

Regardless of what type of diet you follow, or when you like to exercise, there are plenty of ways to add leucine to your healthy diet.

WHY IS LEUCINE IMPORTANT FOR EXERCISERS?

Whether you lift weights, run, swim, or prefer another form of exercise, it is important for you to get enough leucine-rich protein to support muscle maintenance and repair. Leucine is involved in this repair process as it is important in supporting muscle protein synthesis, which can break down during intense exercise.

Leucine is the key BCAA in regulating muscle protein creation as it is an important signaling molecule in muscle protein synthesis, or turnover. Leucine may have anti-catabolic and protein-sparing effects, which slows the body from breaking down protein after an intense workout. Due to its positive effects on older adults, leucine is especially important for exercisers over 40.

The Scientific Evidence for Leucine Supplementation and Exercise

Emerging research indicates that leucine is the key BCAA involved in regulating the genetic signaling pathways involved in muscle protein synthesis. It seems that leucine helps the body slow the process of breaking down protein after a strenuous workout, which is needed for you to build muscle. Research has also shown that leucine upregulates multiple genetic signaling pathways involved in rapid increases in muscle protein synthesis.

For these reasons, it can be a good idea to take a supplement containing leucine before or after lifting weights.

HOW MUCH LEUCINE SHOULD I TAKE?

As we know, leucine can assist in a litany of metabolic functions, including protein synthesis. Dosage, however, depends on the individual: Age, sex, weight, height, caloric intake, and metabolic rate can all dictate your specified, ideal amount of supplemental intake. As always, it never hurts to consult with a doctor or medical professional before taking any supplements regularly. Additionally, refer to the product label of any supplement you intend to take to check for any warnings associated with the product before you take it.

As a generality, the World Health Organization advises that an individual’s daily intake of leucine can be 39 mg per kilogram of body weight.8 For perspective, this would mean a 175-pound (80 kg) person would aim to consume 3.1 grams of leucine per day.