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Glycine: The Muscle-Building, Brain-Boosting Amino Acid

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Glycine benefits - Dr. Axe

While you may not be familiar with the term specifically, you probably already rely on glycine every day to strengthen your body and, frankly, allow it to work properly.

What is glycine used for? This amino acid is essential for many different muscle, cognitive and metabolic functions. It helps break down and transport nutrients like glycogen and fat to be used by cells for energy. In the process, it supports your muscular, immune, digestive and nervous systems.

In the human body, glycine is found in high concentrations in the skin, connective tissues of the joints, and muscle tissue. As one of the key amino acids used to form collagen and gelatin, glycine can be found in bone broth, some types of meat, and other protein sources. In fact, glycine (along with many other nutrients like proline and arginine) is part of what gives “superfood” bone broth its amazing healing abilities.

Amino acids such as glycine can be found in supplement form, too but it’s easy — and probably even more beneficial — to acquire them from natural food sources.

What Is Glycine?

Classified as a “non-essential” (also called conditional) amino acid, glycine can be made in small amounts by the human body itself, but many people can benefit from consuming a lot more from their diets thanks to its numerous beneficial roles.

Nutritional Facts About Glycine:

  • Glycine is the second most widespread amino acid found in human enzymes and proteins, which is why it has roles in nearly every part of the body.
  • It’s one of 20 amino acids used to make protein in the body, which builds the tissue that forms organs, joints and muscles.
  • Of the proteins in the body, it’s concentrated in collagen (the most abundant protein in humans and many mammals) and also gelatin (a substance made from collagen).
  • Some of the most attractive attributes include promoting better muscle growth, healing the lining of the GI tract, and slowing down the loss of cartilage in joints and skin.
  • While high-protein foods (like meat and dairy products) do contain some glycine, the best sources — collagen and gelatin — can be hard to get. These proteins are not found in most cuts of meat and instead are obtained from consuming parts of animals that today most people throw away: skin, bones, connective tissue, tendons and ligaments.
  • People who are ill, recovering from surgery, taking medications that hinder certain metabolic processes or who are under a lot of stress can all use extra glycine for recovery.

Health Benefits

According to some research, glycine can be used to help lower symptoms in people suffering from conditions like ulcers, arthritis, leaky gut syndrome, diabetes, kidney and heart failure, neurobehavioral disorders, chronic fatigue, sleep disorders, and even certain cancers.

Some of the many health benefits of glycine include:

  • helping build lean muscle mass
  • preventing sarcopenia (muscle loss, muscle wasting or deterioration)
  • playing a role in the production of human growth hormone
  • boosting mental performance and memory
  • helping prevent ischemic strokes and seizures
  • protecting skin from signs of aging or cellular mutations
  • protecting collagen in joints and reducing joint pain
  • improving flexibility and range of motion
  • stabilizing blood sugar and lowering risk for type 2 diabetes
  • improving sleep quality
  • lowering inflammation and free radical damage by increasing glutathione production
  • reducing risk for certain types of cancer
  • building the lining of the gastrointestinal tract
  • producing bile salts and digestive enzymes
  • helping reduce allergic and autoimmune reactions
  • boosting energy levels and fighting fatigue, stress and anxiety
  • helping produce red blood cells
  • helping control symptoms of seizures, schizophrenia and mental disorders

Among all of these benefits, here are several key ways glycine is used in the body:

1. Promotes Muscle Growth

Glycine has been found to help inhibit the deterioration of valuable protein tissue that forms muscle and boosts muscle recovery.

In fact, it’s considered as an “anti-aging amino acid” because of how it helps maintain lean muscle mass into old age, stimulates the secretion of human growth hormone, prevents loss of cartilage in joints, and even improves daytime energy, physical performance and mental capabilities (all important for athletes).

Glycine is used during the biosynthesis of creatine, which provides muscles with a direct source of fuel to repair damage and grow back stronger. It also helps provide cells with energy thanks to its role in the conversion of nutrients from your diet, helping feed hungry muscle tissues and boosting endurance, strength and performance.

Additionally, studies suggest it seems to benefit hormone production and regulation, helping the body naturally synthesize steroid hormones that regulate the ratio of fat to muscle mass and control energy expenditure.

2. Repairs and Protects Joints and Cartilage

Together with other amino acids found in bone broth (especially proline), glycine plays a part in the formation of collagen, promoting the growth and function of joints, tendons and ligaments.

Approximately one-third of collagen is composed of glycine, and collagen is crucial for forming connective tissue that keeps joints flexible and able to withstand shock. This is why collagen hydrolysate is often used for the treatment of degenerative joint diseases like osteoarthritis.

As people get older, it’s especially important to consume enough protein (amino acids) in order to repair damaged tissues within joints that suffer due to ongoing free radical damage.

Glycine has been shown in studies to be essential for the formation of stretchy, flexible cartilage, helps heal damaged joints, and can prevent loss of mobility and functionality in older adults.

3. Improves Digestion

Amino acids, including glycine and proline, help rebuild tissue that lines the digestive tract, keeping food particles and bacteria inside the gut where they belong, rather than allowing tiny openings to form that pass particles to the bloodstream where they trigger inflammation.

Glycine helps form two of the most important substances that make up the gut lining: collagen and gelatin.

Collagen and gelatin help people with food allergies and sensitivities tolerate foods more easily, can soothe the lining of the GI tract in people with inflammatory bowel diseases or indigestion (including leaky gut syndrome, IBS, Crohn’s, ulcerative colitis and acid reflux), and even promote probiotic balance and growth.

Within the GI tract, glycine also acts like a metabolic fuel. It’s needed to manufacture bile, nucleic acids, creatine phosphate and porphyrins to be used to break down nutrients from your diet.

For example, it helps break down fats by aiding with the production of bile acids and helps transport glycogen to cells to be used for energy in the form of ATP. Evidence also shows that glycine can help stabilize blood sugar levels, leading to more lasting energy and preventing sugar cravings and fatigue.

There is also evidence from research conducted on rats that “L-glutamine and/or glycine supplementation is beneficial for the repair of the colonic wall of rats, but L-glutamine, with its trophic effects on the colonic mucosa, seems to exhibit better results.”

Glycine benefits - Dr. Axe

4. Slows the Effects of Aging and Builds the Immune System

Glycine helps form glutathione, a valuable antioxidant that’s used to prevent cellular damage and various signs of aging.

A 2011 study published in the American Journal of Clinical Nutrition found that although glutathione deficiency in elderly people occurs because of a marked reduction in synthesis, supplementation with the glutathione precursors cysteine and glycine fully restores glutathione synthesis. This helps increase concentrations and lowers levels of oxidative stress and oxidant damages that lead to aging.

In certain studies, glycine has even been found to help prevent cellular mutations that lead to cancer. There’s some evidence that using targeted amino acid therapy can prevent the growth of cancerous cells by cutting off their energy supply and help turn down inflammation, which is linked to numerous other chronic conditions besides cancer.

This amino acid may also support cardiovascular and metabolic health too. Does glycine raise blood pressure? Most experts believe it doesn’t;  in fact there’s some evidence that glycine supplementation may help lower high blood pressure in patients with the metabolic syndrome or those at risk for heart disease. This is attributed to its ability to reduce free radicals and to increase the availability of nitric oxide.

One study found that higher intake of glycine (in terms of percentage of total protein) was significantly associated with a decreased risk of mortality from ischemic strokes in women. Supplementing with this amino acid following a stroke also seems to help with recovery.

It can also offer protection against type 2 diabetes by increasing insulin sensitivity/protecting against insulin resistance, according to recent studies. In fact it’s been found that glycine levels are lower in patients with obesity, heart disease and/or type 2 diabetes, but that insulin response improves as levels increase.

5. Calms the Nerves and Feeds the Brain

Studies show glycine benefits cognitive performance and the central nervous system because of how it plays a role in the metabolic synthesis of certain nutrients that the brain and nerves use for energy. One example is how it helps regulate nerve impulses throughout the body by balancing electrolyte levels, such as calcium, chloride and potassium.

Is glycine good for anxiety? Yes; due to its role in both nerve and neurotransmitter functions, glycine can improve sleep, mental performance, bodily sensations, moods, memory and behaviors. For example, glycine works with other amino acids, including taurine and gamma-amino butyric acid (GABA), as an inhibitory neurotransmitter.

It may reduce hyperactivity in the brain and even play a role in the treatment or prevention of mental disorders, including learning disabilities, schizophrenia, bipolar disorder/manic depression and epilepsy. It’s also been demonstrated to decrease psychotic symptoms, strokes and seizures when used with other supplements as part of a holistic treatment plan for mental/cognitive illness.

6. Fights Fatigue and Promotes Restful Sleep

Due to its roles in the central nervous system and the digestive system, glycine effects can include helping to boost energy levels, balance blood sugar and prevent fatigue.

Some evidence shows that glycine benefits sleep by boosting serotonin production which decreases anxiety and insomnia.

It can be used to calm anxiety or nervousness that keeps you up at night and gets in the way of getting good sleep — plus it helps directly bring nutrients to cells and tissue for energy at all times of the day.

According to research done by the Japanese Society of Sleep Research, glycine supplements improve sleep quality, lessen daytime sleepiness, and improve performance of memory recognition tasks.

One of its most important effects of glycine is helping carry out the biosynthesis of heme, a component of haemoglobin that helps produce and maintain red blood cells.

Red blood cells help carry oxygen around the body, support cellular functions, and provide the tissue, heart and brain with energy. In fact, glycine is often used in supplements meant to improve energy in athletes, fight fatigue caused by anemia, and help regulate blood sugar levels.

Related: Threonine: The Amino Acid Needed for Collagen Production

Top Foods

Getting more glycine into your diet is probably even easier than you think. What foods are high in glycine? Bone broth is one of the greatest source of naturally occurring glycine and other amino acids, is inexpensive, simple to make at home, and has far-reaching health benefits.

Bone broth — which is made from slowly simmering animal parts, including bones, skin and tendons, in stock — contains natural collagen, which releases important amino acids and other substances that are often missing from the typical Western diet.

However, if you’re not willing to consume bone broth — for example, you’re a vegetarian or vegan — this amino acid can be obtained from plant foods, too.

Plant-based sources include beans; vegetables like spinach, kale, cauliflower, cabbage and pumpkin; plus fruits like banana and kiwi. Other than bone broth, glycine can also be found in “complete sources of proteins” (animal proteins), including meat, dairy products, poultry, eggs and fish.

Don’t forget that it’s also found in high amounts in gelatin, a substance made from collagen that’s used in certain food products and sometimes for cooking or food prep. Gelatin isn’t commonly eaten in large amounts but can be added to recipes when making some gelatin desserts, yogurts, raw cheeses or even ice cream.

Glycine facts - Dr. Axe

Recipes

Here are several simple recipes you can make at home to boost your glycine intake:

Supplements

When it comes to glycine supplements and dosage recommendations, here’s what you need to know:

  • While some foods (especially animal proteins and bone broth) do provide some glycine, amounts tend to be small overall. This is why many can benefit from taking glycine supplements in order to prevent glycine deficiency.
  • There is no established daily requirement or upper limit of glycine at this time. It’s believed that most people already get around two grams of glycine daily from their diets, but needs differ a lot depending on someone’s level of activity and state of health.
  • Depending on the symptoms you’re looking to resolve, you might benefit from consuming 10 times the average amount or even more.
  • Not all protein/amino acid supplements are created equal. The best glycine supplements are those made by reputable companies that use food-based ingredients and no close to no fillers.

Related: Citrulline: The Amino Acid that Benefits Blood Blow and Performance

Risks and Side Effects

Because glycine is a natural amino acid, there’s not much risk for consuming too much from your diet. In supplement form, higher doses of glycine (between 15–60 grams) have been used safely to help resolve chronic conditions like mental disorders without causing side effects. However this amount should be taken with supervision from a doctor.

It’s not known if giving glycine supplements to children, pregnant or breastfeeding women — or people with kidney or liver disease — is safe or likely to cause side effects. This means it’s best to avoid using glycine supplements in these cases for now.

Glycine supplements can also interact with certain medications when taken in high doses (such as those used by people with mental disorders, including clozapine).

Although for most people glycine is very safe (especially in food form), if you take medications it’s always a good idea to get your doctor’s opinion when you begin to use any supplements. Stop using amino acid supplements if you experience side effects like indigestion, restlessness, and so on.

Final Thoughts

  • Glycine is a conditional/non-essential amino acid found in foods including bone broth, meat, poultry, eggs, dairy products and certain beans and veggies.
  • Positive effects of glycine include helping to form collagen and gelatin, substances that are important for building connective tissue throughout the body.
  • This amino acid is beneficial in both food and supplement form for people with joint pain, digestive disorders (like IBS, IBD or food sensitivities), fatigue, trouble getting enough sleep, anxiety, type 2 diabetes, and low immunity.
  • There is no recommended daily amount of glycine or upper limit, but studies have found that it can be used safely in high doses up to 15–60 grams daily when necessary.
  • Estimates show that most people eating a standard Western diet may be experiencing glycine deficiency, as most consume only about two grams from foods daily. This is likely because concentrated sources like animal tendons, skins and bones are often thrown out.
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