Benefits of Proline + How to Get More in Your Diet

By Jillian Levy, CHHC pasted from Dr. Axe website

April 1, 2018 

• What Is Proline?
• Proline Benefits and Uses
• The Best Proline Sources
• Proline vs. Glycine vs. Lysine 
• How to Get Proline in Your Diet + Recipes
• History

Even if there currently isn’t a standard criteria used for for diagnosing “proline deficiency,” certain people can definitely benefit from consuming more of the amino acid. The body makes some of its own proline, plus it is found in “complete protein” foods, but your need for amino acids like proline increases as you age or if you’re experiencing certain health problems.

People with poor skin health, slow healing, joint pain, gastrointestinal problems and a high risk for heart disease can likely all benefit from getting more of this amino acid.

Of all the amino acids that form collagen, proline’s effects on promoting skin health has probably been the most well-researched. (1) What are other benefits of proline? Besides its anti-aging effects and ability to repair damaged skin, other functions of proline include supporting the immune system, improving antioxidant status, improving gut health and nutrient absorption, supporting the metabolism, and protecting the cardiovascular system.

What Is Proline?

Proline is a type of imino acid — very similar to an amino acid, which are often described as the “building blocks of protein.” What type of amino acid is proline? It’s considered to be a “nonessential amino acid” because the human body can synthesize some on its own, unlike certain other amino acids that must be obtained from someone’s diet. For example, glutamate can be used to synthesize proline, although getting it directly from food sources is useful for boosting your levels.

What are the main roles of proline? Functions of proline include helping form collagen, regenerating cartilage, forming connective tissue, repairing skin damage and wounds, healing the gut lining, and repairing joints. The structure of proline is unique because it’s the only proteinogenic amino acid (the types that biosynthetically form proteins) with a secondary amine. Not only does it help with “building” proteins, but it also has a role as a catalyst in many organic reactions. (2)

Proline’s Role in Forming Collagen

One of the reasons that proline is so important is because along with the amino acid glycine, it is the primary amino acid involved in the synthesis of collagen. Here’s how it works:

• Proline is converted into hydroxlysine and hydroxyproline in order to help form collagen, which is the most abundant protein found in the human body and the main component that forms connective tissue.
• Collagen is made up of smaller branched amino acids. It’s formed by linking and winding together branches of amino acids (mostly the types glycine, proline, hydroxyproline and arginine) that together create longer collagen fibers that form tissue. (3)
• Proline amino acids make up about 15 percent of collagen, and proline, glycine and hydroxyproline combined represent more than 50 percent of the total amino acid content of collagen. (4)
• Thanks to proline, our bodies can build enough collagen to support our overall health, since collagen is found nearly everywhere inside the body — including the muscles, teeth, skin, bones, organs, joints, etc.
• The amino acids that form collagen have specific benefits for different parts the body. For example, proline is especially great for skin health and wound healing (in addition to having many other benefits), while glycine can help promote restful sleep, balance blood sugar and repair tendons.

Related: Threonine: The Amino Acid Needed for Collagen Production

Proline Benefits and Uses

1. Helps Heal Wounds and Repair Skin
2. Supports Digestive Health
3. Helps Prevent Joint Pain
4. Supports the Cardiovascular System
5. Contributes to a Healthy Metabolism and Fights Inflammation

1. Helps Heal Wounds and Repair Skin

A major function of proline is helping repair damage to the skin, such as wounds, incisions and burns. It is involved in all three phases of the “wound-healing cascade” as it stimulates cellular migration and contributes to new tissue development. Studies have found that during the early phases of wound healing, wound fluid proline levels are at least 50 percent higher than plasma levels, suggesting active import of proline into the wound site. (5)

Proline does this by supporting collagen synthesis, or the formation of new collagen. Collagen is an essential part of wound healing because it gives structure and strength to our skin. Certain studies have found that collagen supplements, which contain proline, can improve skin barrier function, induce the synthesis of hyaluronic acid, and promote fibroblast growth and migration.

Since your body produces less collagen as you age and this takes a toll on the appearance of your skin, consuming more amino acids that form collagen can be effective for keeping skin looking younger. Proline might also help naturally prevent or treat cellulite. It can help tone, firm and tighten skin, which is why collagen supplements are commonly used for their many anti-aging effects.

2. Supports Digestive Health

Collagen protein has become known as one of the best supplements for improving gut health, treating leaky gut syndrome and therefore supporting overall immune system function. What is the use of proline when it comes to supporting digestive health? The amino acids found in collagen can help strengthen the tissues that line the GI tract, which is beneficial for nutrient absorption and preventing autoimmune responses.

Studies have found that proline and other amino acids found in collagen support the intestine and the gut-associated lymphoid tissue by improving the body’s immune defense and ability to protect against foreign antigens and pathogens. Each amino acid has unique properties that affect gut health, which include: maintaining the integrity, growth and function of the intestines; normalizing inflammatory cytokine secretion; improving T-lymphocyte numbers; and regulating secretion of IgA cells. (6)

3. Helps Prevent Joint Pain 

One reason why aging is often associated with increasing joint pain is because starting in about our mid-30s we begin to produce less collagen. Collagen is necessary for overall physical and mental health, since it literally helps hold the body together and is needed to maintain strength and flexibility of connective tissue. Collagen loss can also be accelerated due to an unhealthy diet, lifestyle and habits, since these lead to higher levels of inflammation, oxidative stress, hormonal imbalances and nutrient deficiencies.

Obtaining more of the amino acids that form collagen, including proline, may help to mitigate these effects by promoting formation of new cartilage, aiding in muscle growth or maintenance, and even helpin improve bone density. Proline and other amino acids can strengthen cartilage by stimulating chondrocytes (the cells of cartilage). Studies conducted on animals have found that proline supports tissue growth and performance. (7) It also aids in many functions of the immune system and can help improve antioxidant status, meaning it may be beneficial for reducing inflammation and oxidative stress, which can damage joints and connective tissue.

4. Supports the Cardiovascular System

Proline can help protect the heart and arterial walls, such as by preventing fat from accumulating in the bloodstream and by controlling blood pressure. Amino acids are needed to form the tissue that constructs blood vessels/arteries. Acquiring more of the amino acids that form collagen may be beneficial for reducing arteriosclerosis risk (thickening or hardening of the arteries).

5. Contributes to a Healthy Metabolism and Fights Inflammation

Proline plays a beneficial role in metabolic functions and synthesis of other compounds. It acts as a signaling molecule and a sensor of cellular energy status. It can help modulate mitochondrial functions, influence cell proliferation or cell death, and trigger specific gene expression, which are all reasons it has been shown to be essential for plants to recover from environmental stress. (8)

Other beneficial effects of proline for energy production and overall health include boosting metabolism and muscle mass, helping with energy output during physical activity, improving the body’s use of antioxidants, facilitating the process of constructing healthy cells from DNA and RNA, supporting phase II liver detoxification, and supporting the central nervous system. A 2017 study conducted on rats found that when rats experienced inflammation, oxidative stress and altered energy parameters in parts of their brains, administration of proline was able to prevent some of these harmful effects. (9)

The Best Proline Sources

What foods are high in proline?

It is found in highest concentrations in natural sources of collagen. The best sources of proline and collagen in the diet are bone broth and other high-protein foods, especially animal products, such as organ meats like liver, grass-fed beef, pasture-raised chicken, wild-caught fish and eggshell membranes.

• When you eat animals “nose to tail,” you consume proline and collagen from parts of the animal, including the bones, connective tissue and muscle tissue.
• Concentrated collagen protein powder and gelatin are two other great sources of proline. Collagen powder is made from sources including chicken collagen, bovine/beef collagen, eggshell membrane collagen and fish collagen. Gelatin is a form of hydrolyzed beef collagen, which means it’s essentially a part of broken-down collagen that is mostly used in desserts or food manufacturing since it creates a gel-like texture.
• Using bone broth or collagen powders/supplements can really come in handy because these save you loads of time and effort. For example, slow-cooked bone broth is made over the course of one to two days, but when you use concentrated bone broth protein powder you can get the benefits of bone broth almost instantly.
• Chicken collagen contains glycine, glutamine and proline, plus chondroitin and glucosamine, two compounds that help rebuild cartilage. You can consume some by eating chicken cooked on the bone with its skin or by making chicken broth, soup, stew and other savory recipes with a variety of animal parts (organs, bones, etc.).
• You can also get small amounts of proline from consuming fish collagen, such as by eating pieces of fish that contain small bones, tissues or scales, or by making fish stock/broth, soup and stew (such as with fish heads).
• Another source is yokes of cage-free eggs. A great way to up your proline/collagen intake is to add some collagen powder to scrambled eggs or a omelette.

Is proline found in plants? Yes, although eating plant foods like vegetables or fruits won’t supply you with very high amount. In plants components, such as pollen, proline accumulation is actually a response to physiological stresses and also involved in structure development.

Proline vs. Glycine vs. Lysine 

What is different about proline compared to other amino acids?

• Approximately one-third of collagen is composed of glycine. Glycine is an amino acid that’s essential for many different muscle, cognitive and metabolic functions. It is one of the main amino acids used to form collagen and gelatin. The best sources of glycine are similar to proline sources, such as bone broth, collagen protein powder and other protein foods.
• Of one glycine’s functions includes helping break down and transport nutrients like glycogen and fat to be used by cells for energy. It’s known as an “anti-aging amino acid” because of how it helps maintain lean muscle mass and stimulates the secretion of human growth hormone. Glycine is used to treat many health conditions, such as muscle wasting (scaropenia), ulcers, arthritis, leaky gut syndrome, diabetes, kidney and heart failure, neurobehavioral disorders, and fatigue.
• Lysine (or l-lysine) is an essential amino acid that is found in protein foods like meat, beans, cheeses and eggs, as well as available in supplement form. Like proline, L-lysine aids in the growth and maintenance of bones and connective tissue by helping form to collagen. It is also very important in the creation of carnitine, which converts fatty acids into energy.
• L-lysine may help repair the digestive system, lower cholesterol levels and be helpful for absorbing calcium, which protects against blood clots and other problems.
• Other benefits attributed to l-lysine include treating cold sores, anxiety, diarrhea and even the development of cancer. The best dietary sources of L-lysine are beef, chicken, turkey, fish like tuna, white beans, pumpkin seeds and eggs.
• Arginine is another amino acid found in collagen. It is found in protein foods, including beef and other types of red meat, poultry, fish, eggs and dairy products. Arginine may offer benefits for heart health, exercise performance, mental capabilities and much more.

How to Get Proline in Your Diet + Recipes

1. Drink Bone Broth

To consume more proline, it’s ideal to drink real bone broth almost daily, which also provides many other nutrients beyond just amino acids. Bone broth is one of the very best ways not only to get more collagen into your diet, but also trace minerals, electrolytes, and beneficial compounds like chondroitin sulfate, glucosamine sulfate and hyaluronic acid.

For the most benefits, aim to have about eight to 16 ounces of bone broth per day. You can make your own homemade bone broth using traditional recipes that take one to two days or by consuming dried or powdered bone broth/bone broth protein. Bone broth can be consumed on its own, added to shakes or smoothies, or used it in all sorts of sweet and savory recipes, such as marinades, stews, or even shakes and smoothies.

2. Take Collagen Powder/Collagen Supplements

You can also use collagen protein in smoothies, shakes or other recipes. I recommend a multi-collagen powder that contains several collagen types, such as types 1, 2, 3, 5 and 10. Each type of collagen has unique functions and benefits, so it’s best to supplement with more than one type.

Collagen is tasteless, odorless and easy to blend into all types of recipes — plus it’s gluten-free, dairy-free, nut-free and soy-free. Add some to baked recipes like muffins, bars or pancakes to increase the protein content. You can also use collagen powder just like gelatin to thicken smoothies, desserts or recipes that have a gel-like texture. Always make sure to purchase a collagen powder that is derived from grass-fed or pasture-raised, healthy animals (ideally that are organically raised).

3. Eat Enough Protein and an Overall Healthy Diet

You’ll get the most benefits from consuming proline and other amino acids found in collagen if you eat a nutrient-dense diet that includes plenty of protein and lots of antioxidants. This is helpful for maintaining higher collagen levels and preventing collagen degradation because it decreases inflammation and free radical damage (also called oxidative stress).

You can boost the amount of proline you absorb and utilize by eating foods that serve as “collagen cofactors,” such as plenty of fresh vegetables, fresh fruits, fresh herbs and spices; various sources of “clean” protein; and foods high in vitamin C, vitamin A, copper and iron.

Below are recipe ideas for adding more proline into your diet:

• Chicken Bone Broth Recipe or Beef Bone Broth Recipe
• 101 Bone Broth Protein Recipes

History

• The imino acid proline was first isolated by a researcher named Richard Willstätter in the year 1900. It was named after pyrrolidine, which is one of the constituents found in proline.
• In humans, this amino acid is synthesized from glutamic acid and other amino acids. It is a constituent of many proteins, especially collagen, which is why proline is supportive of skin, tendons, bones and other types of connective tissue.
• Today it can be taken in isolated supplement form, which is usually labeled as l-proline. Some of the reasons that someone might choose to take proline supplements is if they are dealing with joint/connective tissue pain or various skin problems. While proline supplements have their uses, I recommend getting proline from bone broth or collagen protein, which not only provides proline, but also other amino acids and nutrients too.
• Proline has been shown to play an important role in plants’ response to various environmental stresses. It has natural osmoprotectant properties (it helps organisms survive extreme osmotic stress), so it can be found in a variety of pharmaceutical products or utilized for biotechnological applications. (10) Osmoprotectants are small, organic molecules with neutral charges and low toxicity. They help plants overcome harsh environmental conditions by regulating cellular homeostasis. (11)
• Some studies have found that plants treated with proline show an increase of antioxidant enzymes activities, photosynthetic activity, nutritional status, plant growth and oil content. (12)

Precautions

• There is no established daily requirement or upper limit of proline at this time. Because it is a natural amino acid, there’s not much risk for consuming too much from your diet. If you eat foods high in protein, you likely already get a decent amount of proline from your diet, however consuming more in supplement form is still safe for most people.
• Always look for high-quality collagen, gelatin or bone broth supplements that are sold from reputable companies. Purchase grass-fed, organic products whenever possible.
• It’s not known if proline supplements are always safe for pregnant or breastfeeding women in high doses. If you have trouble digesting protein, have kidney or liver disease , or you’re pregnant, it’s a good idea to discuss supplementing with  proline with your doctor first.

Final Thoughts

• Proline is a non-conditional amino acid, meaning the body makes some on its own while more is obtained from high protein foods.
• Its functions include repairing damage to the skin, supporting the immune system, healing joints, improving antioxidant status, improving gut health and nutrient absorption, supporting the metabolism, and protecting the cardiovascular system.
• One of proline’s most important roles includes forming collagen, the most abundant protein in the human body that gives connective tissue structure and strength.
• The best sources of proline and collagen in our diet are bone broth, collagen powder, gelatin, and other high-protein foods like liver, organ meats, grass-fed beef, pasture-raised chicken, wild-caught fish, egg yolks and eggshell membranes.