It’s important to get leucine in every meal.
What is leucine?
Leucine is an amino acid, one of 20 building blocks that commonly show up in human protein structures. It is also one of nine essential amino acids (EAA), in that we can’t make it in our body and so much consume it in our diet. And lastly, leucine is a branched chain amino acid (BCAA), meaning that unlike 17 of the 20 amino acids with a straight side chain, leucine is one of three where the side chain is forked, or branched. Figure 1 is the structure of leucine.1
What does leucine do?
Leucine is a component of proteins, which when they’re in their ideal location with all of the things they need to work (cofactors like vitamins, minerals and other proteins), become enzymes and do something. BCAAs are found at high levels in skeletal muscle. Leucine also triggers the brain to recognize that you’ve eaten, or cause satiation and the end of eating. In muscle growth, it has been described as “the amino acid that shows up with a cup of coffee and gets everything started,” functioning as a muscle protein synthesis trigger.
How much leucine do you need?
For total protein, the current consensus is 0.3-0.4 g of protein/meal (1.2-2.0g protein/kg per day spread across multiple meals). For leucine, that’s 2.7 g of per meal.2
Where can you fine leucine?
Check out this table of leucine sources.3 Animal muscles are good sources, as it’s is found in high amounts in muscle. But there are many other options as well that are vegetarian or vegan sources. Dairy can also be an excellent source of leucine. Grains tend to be low, with beans being similar to dairy sources per unit volume. Nuts are somewhere between grains and beans/dairy.
Leucine Sources
| Food | Leucine/serving |
| Milk | 0.782g/cup |
| Yogurt, skim, plain | 1.3g/cup |
| Yogurt, Greek, plain, low-fat | 1.06g/7 ounces |
| Cottage Cheese, 1% milk fat | 2.88g/cup |
| Cheddar Cheese | 0.682g/1 ounce slice |
| Whey protein isolate4 | ~10% of total protein, so 2.5g/25gram scoop |
| Beef, ground, cooked | 1.82g/3 ounces |
| Pork chop, lean only, boneless, cooked | 1.83g/3 ounces |
| Chicken breast, boneless, skinless, cooked | 2.25g/3 ounces |
| Chicken breast, bone in, skin on, cooked | 1.96g/3 ounces |
| Bacon | 0.23g/slice |
| Pork sausage | 1.31g/3 oz link or patty |
| White bread, 1 slice | 0.151g/ slice |
| Whole wheat bread, 1 slice | 0.111g/slice |
| Corn tortilla, 6” | 0.109g |
| White rice | 0.176g/half cup cooked |
| Brown rice | 0.216g/half cup cooked |
| Quinoa | 0.242g/half cup cooked |
| Corn | 0.22g/half cup cooked |
| Soy beans/ edamame | 0.28g/half cup cooked |
| Soy milk | 0.26g/cup |
| Tofu, extra firm | 0.73g/3 ounces or 1/5 of a block |
| Soy protein isolate | 1.92g/1 ounce |
| Tempeh | 1.19g/half cup |
| Black beans | 0.61g/half cup cooked |
| Pinto beans | 0.11g/half cup cooked |
| Red beans | 0.54g/half cup cooked |
| Chick peas | 0.42g/half cup cooked |
| Lentils | 0.69g/half cup cooked |
| Split peas | 0.58g/half cup cooked |
| Potatoes | 0.22g/half cup cooked and mashed |
| Sweet potatoes | 0.19g/half cup cooked and mashed |
| Peanuts | 0.481g/1 ounce raw (1/4 cup) |
| Peanut butter | 0.49g/ 2 Tbsp |
| Almonds | 0.418g/1 ounce raw |
| Hazelnuts | 0.301g/1 ounce raw |
| Cashews | 0.417g/1 ounce raw |
| Walnuts | 0.332g/1 ounce raw |
| Creatine | 0g |
How about a comparative graph? Sure! 🙂
Here’s another way of looking at vegan and vegetarian protein sources.2 This graph compares a variety of vegan proteins with animal proteins AND human muscle.
Can you get enough leucine?
If you’re an omnivore, and you eat a mixed meal 3-4 times a day, yes. Piece of cake. Is it possible to get enough if you’re a vegan? Yes, but it takes a little more thought. Here are some sample meals based on the table above.
- 3 ounces grilled chicken breast (2.25g leucine) + ½ C cooked brown rice (0.22g) + ½ C red beans (0.54g) + vegetables would net an athlete 3.01g leucine for a meal.
- A vegan meal might look like a Thai-flavored stir fry with 1 C tempeh (2.38g) on 1 C quinoa (0.48g) + 2T raw peanuts (0.24g) along with the sauce, veggies, and other toppings for 3.1g leucine for the meal.
- Here’s an example of a meal that does NOT have enough. 1 C brown rice (0.43g) + 1 C black beans (1.22g) + a variety of vegetables (low in protein, so minimal leucine) for a total of 1.65g leucine.
Note that for some foods, like corn, leucine might be a high percentage of the total protein (see graph), but the total protein level is comparatively low (see table). So actually get enough of this essential BCAA through corn requires ~5 cups of fresh, frozen or canned corn kernels! It’s not practically useful.
Take home message
As always, get protein at every meal, and ensure that your food combinations provide enough leucine to maximize your muscle building, muscle retention and satiation.
To find out if you’re getting enough of this BCAA, or to ask protein or other sports nutrition questions, contact Dr. Schubert here. Learning more about third party testing and other supplements, like creatine, vitamin D and probiotics is a good thing too!
To find out how your milk compares in terms of protein and other macronutrients, read this recent blog.
Are you a recent bariatric surgery athlete with high protein needs? Find out more about what they are and how to mesh your bariatric needs with your athletic needs.
And if you’re a vegetarian, check out the requirements of a well-planned vegetarian athlete’s diet.
References
- PubChem Leucine (Compound). https://pubchem.ncbi.nlm.nih.gov/compound/Leucine#section=Structures. Accessed February 10, 2021.
- Gorissen, S., Crombag, J., Senden, J., Waterval, W., Bierau, J., Verdijk, L. and van Loon, L., 2018. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids, 50(12), pp.1685-1695.
- FoodData Central. https://fdc.nal.usda.gov. Accessed February 7, 2021.
- Whey Protein Institute, Leucine Content in Common Foods. http://wheyproteininstitute.org/sites/default/files/Leucine-Content-in-Common-Foods.pdf, Accessed 2/8/21.