What are Leucine and Isoleucine

What Are Leucine and Isoleucine?

Leucine: A Protease (Proteolytic) Amino Acid

The name leucine comes from the Greek word “leukos” which means white. Leu-kos is derived from the Latin words “lucere”, meaning white, and “-cide”, meaning to kill or put out of action.

Thus, leucine means white protein. When combined with another amino acid called arginine, it becomes known as lysinate. Lysine is found in many foods such as meat, poultry, fish, eggs and dairy products. L-lysine is converted into lysine by bacteria in the gut. L-lysine acts like a protease enzyme that breaks down proteins.

Isoleucine: An Amylase (Amino Acid Cleavage) Amino Acid

The name isoleucine comes from the Greek word “iros” which means grain. Iso refers to equal or similar and leucine means white hence isoleucine means similar to leucine.

Isoleucine is categorized as a basic (or alpha-amino) amino acid. It can be found in the seeds, grains, and nuts of various plants especially wheat, corn, rice, and rye. It can also be found in human blood and tissues.

What are Branched-chain Amino Acids?

Branched-chain amino acids (BCAAs) are three essential amino acids that human beings cannot produce naturally. These three amino acids are leucine, isoleucine, and valine. They are called branched-chain because their structures have a side chain or “branch” chaining off from the main structure of the amino acid.

Why are BCAAs important?

The human body can produce nine of the twenty kinds of amino acids. The other eleven are considered essential because our bodies cannot produce them and they must be obtained from food sources. If our body does not receive essential amino acids, it cannot build new proteins and this may result in a whole host of complications.

Why are leucine, isoleucine, and valine considered BCAAs?

Leucine, isoleucine, and valine are classified as branched-chain amino acids because their structures have a side chain or “branch” chaining off from the main structure of the amino acid.

What does leucine do in the body?

The body uses leucine as a building block for muscle proteins. In fact, some research says that leucine stimulates protein synthesis better than any other amino acid. It may also increase the body’s production of a substance called insulin-like growth factor-1 (IGF-1). IGF-1 is responsible for helping muscle cells and bones grow. A study has shown that after injecting lab rats with IGF-1, the rats grew bigger muscles.

What does isoleucine do in the body?

Research says that isoleucine helps the body produce energy. It may also help regenerate liver cells.

What does valine do in the body?

Valine is used by the body to build muscle. It also helps the body produce hemoglobin (the substance that carries oxygen in the blood).

How much leucine, isoleucine, and valine do I need?

The recommended dietary allowances (RDAs) for BCAAs are based on a person’s weight. The following chart shows the RDA for BCAAs:

What are Leucine and Isoleucine - at

The table below shows how much leucine, isoleucine, and valine are found in different foods.

Food Serving Leucine Isoleucine Valine Milk (whole) 1 cup 4.053 g 2.912 g 0.945 g Beef 3 oz 3.028 g 1.092 g 0.074 g Broccoli 1 cup 1.976 g 0.628 g 0.064 g

How do I get enough BCAAs?

Meats, eggs, and some dairy products contain significant amounts of leucine, isoleucine, and valine. But if you’re careful with your food choices you may not need to supplement your diet with extra BCAAs. For example, 3 ounces of beef provides about 3.028 grams of leucine, which is only about 2% of your daily needs. By eating a varied diet that includes plenty of fruits, vegetables, and whole grains, you should receive all the leucine, isoleucine, and valine that your body needs.

How can I maximize my intake of BCAAs?

Supplements, such as Branched Chain Amino Acids (BCAAs) can increase your intake of leucine, isoleucine, and valine. A daily serving of one scoop of a BCAAs supplement provides the same amount of leucine found in 2 cups of milk or 4 ounces of chicken. Because each serving provides about 1.5 grams of isoleucine and valine, you would need to take two servings per day to match the amount found in the foods listed under the table above.

Are BCAAs effective for building muscle?

Most studies show that BCAAs are not any better than other amino acids at increasing muscle mass, strength, and exercise performance. One study even showed that taking a BCAA supplement before exercise decreased endurance more than when subjects took a placebo (sucralose). However, this study used a very large amount of BCAAs (6 grams) per dose. Most researchers suggest that BCAAs don’t need to be consumed in supplement form because we get enough of them from dietary sources.

Are BCAAs safe to use for long periods of time?

Leucine, isoleucine, and valine are safe to use for long periods of time. Large amounts of BCAAs can be harmful to people with certain genetic disorders. If you know that you have one of these disorders (known as Maple Syrup Urine Disease), you should NOT take BCAA supplements.

Are there any side effects of using BCAAs?

Most people experience no side effects when taking leucine, isoleucine, and valine. However, some people report feeling nauseous when taking high amounts of BCAAs. Large amounts of BCAAs can also deplete other amino acids in the blood. When this happens, the liver breaks down muscle tissue to obtain these “used” amino acids. Men especially are at risk of developing a condition called “rhabdomyolysis.” Rhabdomyolysis can cause serious kidney damage. If you notice symptoms such as dark urine, muscle pain, or muscle weakness, you should stop taking the supplement and contact your physician immediately.

Do BCAAs cause any interaction effects?

No interactions with BCAAs are known at this time. However, if you are taking any medications or have a pre-existing medical condition, it is always a good idea to speak with your physician before starting a new supplement.

Is there anything else I should know about BCAAs?

If you notice a very fishy odor on your skin, hair, or clothing shortly after taking a BCAA supplement, it could be a sign that you’re not metabolizing the supplement well. If this is the case, your body is breaking down the amino acids in your kidneys and throwing out the “waste products.” To prevent this from happening, consume a combination of carbohydrates and BCAAs during and after exercise. This will suppress muscle breakdown, increase the amount of BCAA oxidation, and ultimately increase the anabolic response from exercise.

Expert Tip: Are BCAAs safe for women?

Although there is no evidence that BCAAs are dangerous for women, research has shown that men benefit more from supplementing with BCAAs than women. One study found that men experienced an increase in muscle protein synthesis when they took a BCAA supplement before and after exercise. The same increase in muscle protein synthesis did not occur in the female subjects. In theory, this means that women do not get as much benefit from taking BCAAs. However, one must remember that this study only looked at women who were exercising. It is possible that women who are not athletes would get the same benefits from BCAAs as men do. Until more studies are done, it is best to limit BCAA supplements to a maximum of 3 grams per day, if you are a woman.



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