What is glycine, and is it good for you? (2024)

Glycine is an amino acid you can get naturally in foods or take as a supplement. Here's what we know about its effects on metabolic health.

Getting sufficientproteinin your diet is crucial for maintaining stable blood sugar, strong muscles, and satiety. But among the 20 individual amino acids that comprise protein, do any have unique metabolic benefits that warrant a higher intake? Getting a bit more buzz lately from functional medicine and health optimization experts likeMark Hyman, MD,Peter Attia, MD, andAndrew Huberman, PhD, is glycine—an amino acid that’s relatively abundant in bothbone brothand collagen powder but that can also be found as a standalone supplement.

While preliminary research (small human trials and animal studies) suggests glycinemay positively influencecardiovascular health, sleep quality, glycemic control, inflammation, and more, findings are inconsistent, and there’s a lot we still need to learn about the long-term safety and efficacy of this amino acid when taken as a supplement. Below, learn more about glycine and its potential perks.

What is glycine?

Glycine is one of the20 amino acidsthat your body needs to function properly. Amino acids are considered the “building blocks” of protein, as they’re used to produce various structural proteins within your body, including the myosin in muscles, collagen, and elastin. Amino acids also play an important role in neurotransmitters, hormones, and enzymatic reactions.

Some amino acids are considered essential and must be obtained from food, as your body can’t produce them (just likeessential vitamins and mineralsmust be obtained from food). But glycine is primarily considered a non-essential amino acid because the body can produce it fromprecursorslike choline and the amino acids serine and threonine. Sometimes, however, glycine (along withseveral other amino acids) is “conditionally essential,” meaning your body may not be able to keep up with production during times of illness and stress, so you’ll need more fromdietary sourcessuch as meat, fish, dairy, and legumes.

Glycineplays many rolesin the body. To name a few:

How might glycine affect metabolic health?

Glycine and Sleep Quality

While glycine is touted for a range of benefits, the perk repeatedly mentioned by health experts is better sleep. In fact, health and longevity expertsPeter Attia, MD, andAndrew Huberman, PhD, both take 2 g of glycine (along with other supplements likemagnesium) several nights per week to support sleep. Although Dr. Attia acknowledged ina 2022 podcast episodethat data on glycine and sleep isn’t substantial yet, there are a couple of small studies to support the connection.

Ina small 2006 study, 15 participants with chronically poor sleep quality experienced greater subjective improvements in fatigue and felt more clear-headed upon waking after taking 3 g of glycine for four nights within an hour before bedtime compared to a placebo; and ina small 2007 study, the same evening dose was associated with faster sleep onset, subjective improvements in sleep quality, and decreased daytime sleepiness among 11 participants. Animal studies suggest the mechanism behind glycine’s sleep-enhancing effect may be its ability tobind NMDA (N-methyl-D-aspartate) receptorsin the brain, which researchers speculate increases peripheral vasodilation (i.e., widening of the blood vessels) and leads to a subsequent reduction in core body temperature by increasing blood flow throughout the body and to skin—and a reduction in core body temperature, in turn, is thought to support sleep. It may also play a role insupporting the production of serotonin,a precursor to melatonin.

Quality sleep, in turn, is incrediblyimportant for glycemic controland regulating appetite. In fact, several studies have found that just one night of poor sleep maypromote insulin resistanceand impair glucose processing the next day, as well asincrease hunger and food cravings, possibly by ramping up production ofthe hunger hormone ghrelin.

Glycine, Glutathione, and Oxidative Stress

Your body needs glycine, along with the amino acids cysteine and glutamine,to make glutathione—a powerful antioxidant that helps neutralize reactive oxygen species (a type of free radical) caused by factors like poor diet, stress, and pollution that might otherwise contribute to a disease-promoting state of oxidative stress. Keeping oxidative stress in check is important, as it’sbeen linked toinflammation, insulin resistance, complications of diabetes and metabolic dysfunction,cancer, as well as painful conditions that limit mobility likeosteoarthritis. All of this is to say that maintaining healthy levels of glutathione is in your best metabolic interest.

Glycine is considered “rate-limiting” for glutathione production—so when you have less glycine in your diet, your body produces less glutathione. Some experts believe supplementing with a combination of glycine and cysteine in the form of N-acetyl-cysteine (NAC) can boost glutathione synthesisto a greater extentthan taking either amino acid alone—which makes intuitive sense since both are required for glutathione synthesis. In turn, the theory goes, this may help improve insulin resistance, diabetes complications, and issues associated with oxidative stress.

Ina 2023 study, older adults who supplemented with a combination of glycine and NAC dubbed “GlyNAC” for 16 weeks at a dose of 100 mg/kg per day each had an increase in glutathione levels and improvements in markers of oxidative stress, insulin resistance, inflammation, mitochondrial function, walking speed, and other markers of aging.

But while this research appears to support the indirect antioxidant benefit of glycine and cysteine together (via increased glutathione), studies have not yet sussed out glycine’s benefit specifically.

Glycine and Inflammation

Untamed inflammation is at the root of nearly every chronic disease, including cardiovascular disease and diabetes—and glycine may influence its progression.Preliminary studieson animals and cell cultures suggest that glycine exerts an anti-inflammatory effect by downregulating the pro-inflammatory NF-κB pathway, which results in reduced production of pro-inflammatory cytokines and increased production of anti-inflammatory cytokines. Supplementing with glycinehas been proposedas a way to potentially treat conditions with low-grade inflammation, such as obesity. However, there’s no research yet on humans establishing an ideal intake or supplemental dose to promote this anti-inflammatory effect.

Glycine and Blood Glucose

Maintaining stable blood sugar in a healthy range is one of the most effective ways to support metabolic health (which is why continuous glucose monitors [CGMs] can be so effective). A2008 studyon 74 adults with Type 2 diabetes found that supplementing with 5 g of glycine three times per day (15 g per day) for three months was associated with significant reductions inHbA1c(-1.4%) compared to a placebo group (-0.4%), although the mechanism is unclear. HbA1C is a marker of average blood sugar over three months. There were also reductions in fasting glucose and increases in fasting insulin, but these didn’t reach statistically significant levels.

Findings aren’t entirely consistent from trial to trial, however. A2013 studyon 52 adults with metabolic syndrome who also took the same dose of 5 g of glycine per meal (15 g per day) for three months found that although HbA1C levels dropped more in the glycine group (along with systolic blood pressure and markers of oxidative stress), fasting glucose levels actually increased—and this increase was more pronounced for women. Though unclear why, researchers speculate it could be due to increased gluconeogenesis, or the process by which the liver and kidneys create new glucose. More research is needed on the long-term impact of glycine supplementation on glycemic control.

Glycine and NAFLD

Non-alcoholic fatty liver disease (NAFLD) can be triggered by a high-calorie, high-sugar diet, and it’s often considered the liver manifestation of metabolic syndrome. Plasma glycine levels may be around9-13% lowerin patients with NAFLD, butanimal studiessuggest supplemental glycine could help reduce liver fat accumulation—possibly by boosting levels of the hormones GLP-1 and glucagon, which work in complementary ways toenhancefatty acid beta-oxidation and counter the formation of fatty acids in the liver. However, more research on glycine and fatty liver in humans is needed.

Glycine and Cardiovascular Health

A2015 studyon more than 4,000 adults found an association between higher plasma glycine levels and a lower risk of heart attack after a median of 7 years. As mentioned, glycine appears to help curb oxidative stress and inflammation—and both of these processes can promote cardiovascular disease. However, research is mixed on glycine and stroke risk, withone studysuggesting it may reduce the risk of stroke by regulating inflammation and aspects of glucose metabolism, whileanotherfound that high-glycine diets were associated with an increased risk of death from stroke in men (but not women).

Glycine and Collagen Production

Glycine plays an important role in the creation ofcollagen, the most abundant protein in the body, forming a vital component of muscles, tendons, ligaments, and cartilage injoints, bones, and skin. The integrity of these tissues is important for so many reasons, including enhancing and maintaining functional capacity—in other words, ensuring you’re able to move andexercisecomfortably, which is crucial for metabolic health.Researchon cell cultures suggests that quantities of glycine exceeding what the body can make on its own may help optimize collagen production by cartilage cells, which could help prevent or treat conditions that limit functional capacity, such as osteoarthritis. But again, no effective or recommended dose has been established for this in humans.

How much glycine do you need?

This question is tricky to answer since glycine is technically non-essential (i.e., the body is capable of making it), and yet some research suggests we may benefit from getting more. Here’s what we do know: The body produces around2.5-3 gof glycine per day from precursors like the amino acid serine, and most people consume around1.5-3 gof glycine directly from animal and plant protein sources. But some researchers believe this cumulative 4-6 g of glycine per day may not be enough to optimally meet the body’s demands—ina 2009 report, authors write that an average 70 kg (154 lb) adult requires about 15 g of glycine per day to optimally support the synthesis of collagen and other proteins and metabolites. Meaning, we could fall about 10 g short, and it may be worth supplementing to ensure a healthy metabolism, per the authors.

However, the idea that glycine supplementation is necessary for optimal health isn’t widespread, and based on some of the mixed results from the studies above (and the general shortage of high-quality clinical trials), experts haven’t identified optimal doses for various situations.

While prioritizing your dietary intake ofproteinand glycine-rich foods (more on those below) in general is likely a safe way to get a bit more glycine in your diet, the implications of long-term supplementation, especially at higher doses, are not clear. In general, requirements for different nutrients vary based on your individual health, so it’s best to work with a medical professional who is familiar with glycine to identify the best dose for you.

How do you test your glycine levels?

There’s no widely available glycine test. However, some functional medicine practitioners may use organic acid testing (OAT) to identify increased demand for glycine and other nutrients. OAT measures the levels ofdifferent organic compoundsin urine that are produced via a variety of important biochemical pathways, including 5-oxoproline (or pyroglutamic acid), a metabolite of the antioxidant glutathione. Some research suggests that elevated levels of 5-oxoproline may indicate glutathione depletion and an increased demand for glycine (a glutathione precursor).

Keep in mind: This type of testing tends to be expensive and not covered by insurance, and it may not be practical or necessary for most people. If interested, it’s worth seeking out the opinion of a reputable functional medicine practitioner. In conventional medicine, OAT is widely usedto identify inborn errors of metabolismin newborns, but it’s typically not used in adults.

What are the best foods for glycine?

Glycine is an amino acid, and amino acids are found in proteins—so prioritizing adequate protein intake is your best overall strategy for naturally boosting glycine levels. In anolder study from 1980, researchers found that a total daily protein intake of 1.5 g/kg led to increased dietary intake of glycine and increased glycine synthesis in the body compared to an intake of 0.4 g/kg.

Some protein-containing foods with higher glycine contentincludevarious fish, meats, dairy products, and legumes. Here are some important factors to consider:

  • Glycine is particularly concentrated in thecollagen-rich bone, skin, and connective tissueof animals, which is whybone broth,gelatin, andcollagenare considered good sources.
  • A serving of a popular brand of collagen peptides has3.7 g glycine(and their gelatin has3.5 g), which is a bit more than the amount of glycine used in the sleep studies above.
  • The amount of glycine and other amino acids in bone broth will vary based on how it was prepared; one popular brand states their products have1.9 g glycineper serving.
  • Tougher cuts of meats that require slow cooking, such as brisket and chuck and shoulder roasts,contain more collagenand, therefore, more glycine.
  • As for plants, soybeans appear to have the highest levels of glycine, with around673 mg per cupof prepared edamame.

Just remember, because glycine can be synthesized from other amino acids, prioritizing protein in general may be more realistic than simply seeking out high-glycine foods.

What about glycine supplements?

Glycine supplements are available as capsules and powders and typically come with recommended doses of1 to 3 grams per day. You can also find combinationglycine and NAC supplements (with 1.8 g each), like the ones used in the glutathione studies mentioned above. It may be worth proceeding with caution at higher doses—and remember, experts like Attia and Huberman have said they stick to a relatively low 2 g/day dose.

Based on the information presented in this article, it’s hard to say for sure if we’re getting optimal amounts of glycine from food or if supplementing is worth it. For the studies mentioned above, glycine taken in doses of 3-15 g for up to three months appears to be safe, but there hasn’t been much research into the long-term safety of glycine supplements. Some sources caution against taking single amino acid supplements due to the fact that large doses of onemay lead to poor absorption of others, but it’s not clear if this would happen with glycine supplements.

Choosing a collagen powder (which has more glycine than a typical protein powder) could be a smart way to boost intake of glycine along with other amino acids. These are typically flavorless and dissolve in liquids, making them easy to incorporate into a variety of food and beverages.

If you choose to supplement, seek out brands that have been third-party tested by an independent organization and discuss proper dosing for your needs with a healthcare provider. (Attia usesThorne Glycineand doesn’t have a financial stake in the company).

As with nearly all supplements, women who are pregnant or breastfeeding shouldavoid taking glycinesupplements before first talking with their doctor.

What is glycine, and is it good for you? (1)Get a better view of your metabolic health

The best way to understand how well your body processes your diet is with a continuous glucose monitor and an app like Levels to help you interpret the data. Levels members get access to the most advanced CGMs and personalized guidance to build healthy, sustainable habits. Click here to learnmore about Levels.

What is glycine, and is it good for you? (2024)
Top Articles
Latest Posts
Article information

Author: Manual Maggio

Last Updated:

Views: 6452

Rating: 4.9 / 5 (49 voted)

Reviews: 88% of readers found this page helpful

Author information

Name: Manual Maggio

Birthday: 1998-01-20

Address: 359 Kelvin Stream, Lake Eldonview, MT 33517-1242

Phone: +577037762465

Job: Product Hospitality Supervisor

Hobby: Gardening, Web surfing, Video gaming, Amateur radio, Flag Football, Reading, Table tennis

Introduction: My name is Manual Maggio, I am a thankful, tender, adventurous, delightful, fantastic, proud, graceful person who loves writing and wants to share my knowledge and understanding with you.