Glycine: Benefits and Side Effects

Glycine is an amino acid that supports nerve signal transmission, as well as helping to structure bones, muscle, and connective tissue. It may also benefit mood, memory, sleep, stroke recovery, and heart disease, among other conditions, but more study is needed to identify and confirm potential benefits of glycine.

Glycine Benefits

Glycine is an amino acid that serves as a building block for specific proteins, including collagen, a structural protein found in connective tissues. Glycine makes up around 33% of the collagen in the human body. It also binds to toxins to clear them from the body.

There’s some evidence that glycine supplementation can prevent and treat disease as well as enhance the quality of sleep and neurological symptoms. Research studies on benefits include:

• Mood: Glycine stimulates the production of serotonin, the “feel-good” hormone that helps elevate mood and enhance memory. Studies on rodents have demonstrated that glycine supplementation increases serotonin levels.
• Improved sleep: Multiple studies suggest that glycine can help to improve sleep quality and reduce fatigue. It’s thought that glycine acts on N-methyl-D-aspartate (NMDA) receptors in the suprachiasmatic nucleus, the master circadian pacemaker responsible for controlling sleep.
• Schizophrenia symptoms: Researchers have looked at how glycine might treat schizophrenia, a mental illness that causes delusions, hallucinations, and unusual behavior. A 2016 review of studies found conflicting evidence, but glycine may limit the side effects of medication used to treat this mental health disorder.
• Risk of ischemic stroke: Healthcare providers sometimes prescribe glycine to people who have just had an ischemic stroke. A study in 2020 concluded that glycine improved outcomes of ischemic stroke (caused by a blood clot rather than bleeding), but studies show mixed results.
• Heart disease: Glycine is anti-inflammatory and antioxidative (meaning it prevents or slows cell damage), which are properties that reduce heart disease risk. More study is needed, but researchers have found links between lower glycine levels in the blood and higher risks of high blood pressure and heart disease.
• Improved glutathione synthesis: Glutathione is an antioxidant found in every cell in the body. It’s made in the liver and has many important roles, including regenerating vitamins E and C, helping certain enzymes function, and supporting the immune system. Research has shown it can slow cancer progression and reduce cell damage caused by other diseases. Glycine is needed to produce glutathione, and supplements may help to support function.

In addition to the potential health benefits listed above, some people use glycine to support:

• Enlarged prostate
• Leg ulcers
• Liver damage, especially alcohol-induced
• Insulin resistance and type 2 diabetes
• Enhance muscle protein mass

What Are the Risks and Side Effects of Glycine?

Your healthcare provider may recommend you take glycine to support your sleep or mood or lower your heart disease or stroke risk. However, consuming a supplement like glycine may have potential side effects that include:

Since studies have found that glycine supplements interact with antipsychotic drugs, like Clozaril (clozapine), you should talk to a healthcare provider before taking glycine if you are taking these medications.

The following people should avoid glycine:

• Children
• Pregnant people
• Those who are breastfeeding

It is essential to carefully read the ingredient list and nutrition facts panel of a supplement to know which ingredients and how much of each ingredient is included. In addition, review this supplement label with your healthcare provider to discuss any potential interactions with foods, other supplements, and medications. 

Dosage: How Much Glycine Should I Take?

Glycine is available in several different formulations:

• Oral gel caps, typically available in 500 milligrams (mg) to 1,000 mg doses
• Powdered formulations that you can add to shakes or smoothies
• Topical creams containing glycine and the amino acids L-cysteine and DL-threonine, available by prescription for leg ulcers

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs. 

What Happens if I Take Too Much Glycine?

Glycine toxicity from supplements is rare. However, it can occur when used with sterile water for bladder irrigation. In this situation, a healthcare provider administers glycine, usually after prostate or bladder surgery, to prevent or flush out blood clots.

Signs of glycine toxicity include:

• Visual disturbances
• Drowsiness
• Vomiting
• Weakness
• Prickling skin sensations
• Skin flushing

Glycine toxicity can be fatal.

Sources of Glycine and What to Look For

Glycine is readily available in plenty of foods. You can also take it in supplement form.

Food Sources of Glycine

You can find glycine in high-protein foods. Good sources of glycine-rich foods include legumes, fish, dairy, and meat.

Some of the best food sources of glycine include:

• Red meat: (1.5 to 2 g per 100 g serving)
• Seeds (1.5 to 3.4 g per 100 g)
• Turkey (1.8 g per 100 g)
• Chicken (1.75 g per 100 g)
• Pork (1.7 g per 100 g)
• Peanuts (1.6 g per 100 g)
• Canned salmon (1.4 g per 100 g)
• Granola (0.8 g per 100 g)
• Quinoa (0.7 g per 100 g)
• Hard cheese (0.6 g per 100 g)
• Pasta (0.6 g per 100 g)
• Soybeans (0.5 g per 100 g)
• Bread (0.5 g per 100 g)
• Almonds (0.6 g per 100 g)
• Eggs (0.5 g per 100 g)
• Beans (0.4 g per 100 g)

Glycine Supplements

Glycine supplements come in capsules or powder formulations. Some people prefer capsules because they are easy to take. Others incorporate powders into shakes or smoothies.

Supplements are typically vegetarian or vegan. However, read the label carefully for allergens like wheat or eggs if you have food allergies.