Leucine is an amino acid that plays a unique role in your body’s metabolism.

It’s for muscles and a whole lot more

Like all other amino acids, leucine is needed to build protein. You need adequate protein, including leucine as one component, to be sure your have the raw materials to build muscle.

Though muscles are the body’s largest storehouse of protein, and maintaining muscle mass is important to health, proteins are needed everywhere else in your body, too. 

Here’s an example. The cells lining the intestine turn over rapidly and constantly need to be replenished. Not enough protein? The intestinal lining is less robust, and your nutrient absorption suffers. You also become prone to food sensitivities because you don’t have an intact barrier to keep large, allergy-triggering molecules out of your general circulation.

Leucine switches on protein synthesis

Leucine is foremost among amino acids when it comes to protein fabrication. Like other amino acids, it’s one of the necessary raw materials, but it has a hormonal role too. After you eat, leucine signals your chemistry to accelerate the translation of genes into protein.

Without adequate leucine intake, amino acids aren’t efficiently snapped up for protein building. Then their default fate is to be converted into carbohydrate or fat to be stored in fat cells. 

Leucine zips directly into your blood

Most of the food you eat is digested and absorbed into the blood vessels of the small intestine. From there it filters through the liver, where a host of enzymes go to work on it. Most amino acids are altered in the liver and then sent out to the rest of the body.

But leucine is different.

The liver lacks the enzymes that process leucine (and the other branched-chain amino acids valine and isoleucine.) Instead, leucine passes unaltered into the blood stream. That means your muscles and other body cells get a jump-start in putting to use the protein component of the meal you’ve just eaten.


Leucine is one of the “essential” amino acids. Your body can’t manufacture it; you’ve got to consume it in foods.

Good food sources include poultry, meats and fish, beans and dairy products. Many people get plenty in their diet. But there are situations in which your leucine intake might be inadequate: if your diet is sketchy, if you’re a strict vegan, if you’re recovering from illness or an injury, if your body composition is seriously out of balance (too much fat!) or if you’re actively trying to build your athletic capabilities.

Protein powder

Another option to ensure you get optimal amounts of leucine is a protein powder supplement. Many people enjoy a shake or smoothie with added protein powder, either as a supplemental source of protein or even as a meal replacement.

A wide variety of powders are on the market with protein from a variety of sources: soy, hemp, meat, pea, whey, and more. The supplement with the most leucine is from whey.

25 g of whey protein powder contains 2.7 g of leucine. By contrast, you’d have to consume 31 g of corn-derived protein powder in order to get 2.7 g of leucine. Other plants have even less.

If you have trouble digesting milk

Even if you have trouble digesting milk, whey protein is most likely to be just fine for you. That’s because most people who have trouble digesting milk have trouble with the sugars found in milk – lactose – not the protein component.

And even for those who have a negative reaction to the protein in milk – a food allergy – most often it’s not because of whey but because of the other main family of proteins found in milk, casein.

Here’s the whey supplement I recommend most often. I like it because there’s no added sugar or other ingredients.

If you’d like to get some, you can:

  • Let me know and I can order it for you, or
  • Order it through my online dispensary Fullscript

Dr. Lavine has been an innovator in the use of movement and touch to promote health since 1981. He practices in New York City and Princeton, NJ.


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