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Many people wonder why animal proteins are so important. After all, can’t you combine beans and rice and eat plenty of soy protein to get enough protein? While technically, you can get enough protein from all plant foods, there’s a stark difference in the protein quality. An amino acid called leucine has a lot to do with it.

What is Protein Quality?

Protein quality refers to how well a protein source provides the amino acids needed for basic physiological function. These may include growth, repair, and maintenance of tissues. Several factors contribute to protein quality. The amino acid composition, digestibility, bioavailability, and use all play in. [1]

One aspect of protein quality is how well a protein source provides the essential amino acids the body cannot produce on its own. A high-quality protein source contains all nine essential amino acids in adequate amounts. Animal-based proteins, such as those found in meat, poultry, fish, eggs, and dairy, are considered complete proteins. Therefore, they’re also deemed “high quality.” [2]

Plant-based proteins, like those found in beans, lentils, and grains, are usually incomplete. However, they can be combined to achieve a complete amino acid profile. [3] That’s why beans and rice are often a staple meal in many traditional cultures.

Keep in mind, though, that you’ll also be getting plenty of carbohydrates when relying on plant-based protein sources. That can create problems if you’re at all having glucose or insulin issues, such as hypoglycemia or diabetes. Again, that’s where animal proteins come in.

Where Does Leucine Come in?

Leucine is one of the nine essential amino acids (EAA) that must come from foods because the body cannot make them on its own. Leucine is also one of the three branched-chain amino acids (BCAAs), along with isoleucine and valine.

BCAAs are known to play a crucial role in stimulating muscle protein synthesis. So, they are critical for maintaining and building lean body mass. [4] BCAA and leucine supplementation are often used in the context of sports nutrition. Athletes will take these amino acids as supplements to improve their protein synthesis rates.

Of the three BCAAs, leucine is the strongest “trigger” of muscle protein synthesis. [5] It activates specific signaling pathways that promote the growth and repair of muscle tissues. But to get this effect, you have to consume about 3-5 grams (depending on body weight) to stimulate muscle building. [6]

Our cells can sense leucine concentrations in the body. When enough leucine is present, the cells trigger an enzyme called the “mechanistic target of rapamycin” (mTOR). This protein directly activates the body’s mTOR complex 1 (mTORC1) pathway to stimulate protein synthesis. [7] Essentially, if you get enough leucine, you’ll start repairing and building muscle.

Leucine is also important for preventing the muscle wasting (sarcopenia) typical in older adults. One study showed healthy older men increased their protein synthesis and muscle growth by supplementing leucine. [8][9]

However, supplementing leucine in its isolated form can only go so far. It’s far better to get protein through including leucine-rich whole foods, as you’ll see below.

Leucine-Rich Foods

Foods rich in leucine include animal proteins such as meat, poultry, fish, eggs, and dairy products. Plant-based sources like soybeans, lentils, and quinoa also have leucine but in smaller amounts. [10] A high-quality protein source rich in leucine is considered optimal for supporting muscle protein synthesis.

Whey protein or whey protein isolate is often promoted for its high leucine content and overall amino acid profile. However, at The Wellness Way, we discourage getting your protein from cow’s milk sources. There are plenty of other animal proteins that are rich in leucine.

Here are some dietary proteins that are also excellent sources of leucine:

  • Chicken Breast: Chicken breast is a lean source of protein that is also rich in leucine.
  • Turkey: Like chicken, turkey is a poultry option that provides a good amount of leucine.
  • Beef: Beef, especially lean cuts, is a rich source of leucine.
  • Fish: Various fish, including wild-caught salmon and tuna, are good sources of leucine. Salmon and other cold water fish are also high in inflammation-lowering omega-3 fatty acids.
  • Eggs: Eggs, especially egg whites, contain leucine and other essential amino acids. Depending on your food allergies, you can opt for chicken, duck, or even quail eggs.

The leucine content of foods can vary, so combining many protein sources can help ensure you’re getting your ideal amount of protein each day.

Protein quality and leucine content become particularly important in situations where muscle preservation or growth is a priority, such as during periods of exercise, recovery from illness, or aging, when maintaining muscle mass becomes crucial.

Health Restoration, Protein Quality, and Leucine

As mentioned, getting high-quality protein with adequate leucine is important when recovering from an illness. If you’re currently working on restoring your health, increasing your daily protein intake is essential.

However, it can be difficult to get it all from eating whole foods! Protein is very satiating, after all. So, you may find yourself pushing away from the table before finishing all those high-protein foods. That’s where supplementation may help. Protein supplements like Bone Broth protein or hemp protein can help you increase your total protein intake by getting it in liquid form.

Don’t forget about physical activity! Resistance exercises like weightlifting and using resistance bands can also improve the anabolic response (building up) of the skeletal muscles. Resistance training works with a healthy diet rich in protein content to improve body composition and overall health. [11]

The Wellness Way is Here to Help!

Focusing on protein ingestion is only one small part of the health restoration puzzle! There’s much more to it than that. Working with a Wellness Way doctor or coach can help you discover what other nutrients you may be missing. Thorough food allergy testing can also help you make necessary adaptations to an already healthy diet. After all, whey protein won’t do you any good if you have a dairy allergy or can’t break down casein.

Get tested, start a personalized nutrition program, and restore your health and energy. Contact a Wellness Way Clinic today!


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Disclaimer: This content is for educational purposes only. It’s not intended as a substitute for the advice provided by your Wellness Way clinic or personal physician, especially if currently taking prescription or over-the-counter medications. Pregnant women, in particular, should seek the advice of a physician before trying any herb or supplement listed on this website. Always speak with your individual clinic before adding any medication, herb, or nutritional supplement to your health protocol. Information and statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease.

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