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17 Benefits of Glycine Supplements + Dietary Sources

Written by Puya Yazdi, MD | Last updated:
Jonathan Ritter
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology) | Written by Puya Yazdi, MD | Last updated:

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Glycine Supplement
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Glycine is an amino acid, one of the basic building blocks of proteins, which may have a variety of health benefits. What does the science say?

What is Glycine?

Glycine is one of many amino acids that are used to produce proteins. It is the smallest of all amino acids and is incredibly important for the synthesis of other amino acids, glutathione, creatine, heme, RNA/DNA, and it can also help with the absorption of calcium in the body [1, 2].

Dietary Requirements

Glycine is sometimes called a semi-essential nutrient because it is made by the body, but not in sufficient quantities to supply various tissues (including bone, muscle, and skin) with what they need. Therefore, we need to get quite a bit of glycine from our diets to stay healthy.

The average person usually can make roughly 3g of glycine, and usually consume 1.5 – 3.0 g from food, making their daily intake from roughly 4.5 – 6g [3].

Some researchers believe that the amount of glycine available in humans might not be enough to meet metabolic needs and that a dietary supplement is appropriate [3].

One study suggests that humans may fall significantly short of the amount needed for all metabolic uses – by about 10 g per day for a 70 kg (154 lbs) human [3].

Glycine is a “semi-essential” amino acid; the human body can produce some on its own, but we also need to get some from our diet. The smallest amino acid, glycine is essential for the production of many important compounds, including DNA.

Benefits of Glycine

Despite the presence of glycine in most protein-containing foods, glycine supplements have not been approved by the FDA for medical use and generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.

Possibly Effective For

1) Skin Health

Glycine (through the consumption of collagen) significantly improved skin elasticity in elderly women and improved skin moisture and water loss [4, 5].

Collagen peptide, which contains a lot of glycine, suppressed UV-B induced skin damage and photoaging [6].

Women taking 2.5g of collagen peptide for 4 weeks significantly reduced eye wrinkles by 20%, with positive effects lasting after the study ended [7].

At 8 weeks, collagen significantly improved skin content of procollagen type I by 65%, and elastin by 18%.

Diabetic Ulcers

Glycine nearly doubles the speed at which skin ulcers heal in 89 diabetic patients across 23 long term care facilities [8].

Glycine enhanced wound healing in diabetic animal models as well [9].

Glycine in combination with l-cysteine and dl-threonine topically applied to leg ulcerations significantly improved the degree of wound healing and decreased pain [10].

Glycine’s best evidence of benefit comes for its effect on diabetic leg ulcers. Nevertheless, additional research is required before it will be considered sufficient to support a medical claim.

2) Mental Illnesses

Schizophrenia

Glycine supplementation significantly reduced symptoms of schizophrenia [11].

In treatment-resistant schizophrenia glycine improved cognitive and depressive symptoms (dosed at 0.8g/kg).

The group who made the most improvement were also the most deficient in glycine [12].

Glycine helps in chronic schizophrenia by increasing NMDA-receptor-mediated neurotransmission [13].

This effect on NMDA-receptor-mediated neurotransmission allows for glycine to work synergistically with schizophrenia medication [11].

OCD

Glycine supplementation has been shown in one instance over the course of 5 years to significantly reduce symptoms of OCD and body dysmorphic disorder [14].

Glycine has positive results when used in the treatment of obsessive-compulsive disorder in adults [15].

Depression

Depression is associated with lower levels of blood glycine, as well as high levels of taurine [16].

Glycine is most likely to be beneficial for people with schizophrenia and could be beneficial for people with other types of mental illness. Additional human trials will be required to determine glycine’s potential role in mental health.

3) Brain Health

Small amounts of glycine have been shown to dilate the microvessels in the brain by up to 250% [17, 18].

In rats with alcohol poisoning, glycine was able to reduce the accumulation of cholesterol, free fatty acids, and triglycerides in blood circulation, liver, and brain. Ultimately, this decreases swelling in the brain [19].

A shortage of glycine in the brain can negatively influence the brain neurochemistry, synthesis of collagen, RNA/DNA, porphyrins, and other important metabolites [20].

Stroke

In ischemic stroke patients, taking glycine 1 – 2g/day normalized autoantibodies, reduced glutamate and aspartate levels, increased GABA concentrations, and reduces lipid peroxidation [21].

Those who consume regularly low doses of glycine actually reduce damage in future strokes [21].

The glycine treatment at the dose of 1 – 2g/day was accompanied by a tendency to a decreased risk of dying over 30-days [21].

500mg/kg glycine combined with 500mg/kg Piracetam improved cognitive impairments and promoted recovery in the prefrontal cortex in animals with a stroke [22].

There is relatively good evidence that glycine could play a role in stroke prevention and recovery; larger, more robust, and more specific human trials will be required.

Insufficient Evidence For

The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of glycine supplements for any of the below-listed uses. Remember to speak with a doctor before taking glycine supplements, and never use them in place of something your doctor recommends or prescribes.

4) Sleep and Fatigue

Taking glycine before sleep improves sleep quality and sleep efficacy by shortening the time to fall asleep while increasing restorative, slow-wave deep sleep [23].

After taking glycine for sleep, the following day subjects had lessened daytime sleepiness and improved performance of memory recognition tasks [23].

Glycine helps improve REM sleep and decrease non-REM sleep [24].

3g Glycine given to volunteers before sleeping resulted in improvements in fatigue, ‘liveliness and peppiness,’ and ‘clear-headedness’ [25].

Glycine appears to improve daytime sleepiness and fatigue induced by sleep deprivation [26].

Glycine affects certain neuropeptides in the SCN (suprachiasmatic nucleus) in the region in the hippocampus which regulate the circadian rhythm [26].

Specifically, glycine increases VIP, which is critical to the circadian rhythm.

This effect on the SCN indirectly contributes to reducing sleepiness and fatigue induced by sleep restriction [26].

In clinical studies, glycine supplementation reduced daytime sleepiness and fatigue and made people feel more lively and clear-headed after sleep deprivation.

5) Gut Health and Ulcers

Glycine dramatically increased the tolerability of Aspirin in the upper GI tract of 20 healthy human volunteers [27].

Glycine inhibits stomach acid secretion and protects against chemical and stress-induced ulcers [28].

Glycine possesses significant anti-ulcer activity [29].

Glycine prevents chemically induced colitis in animal models [29].

Glycine prevents alcohol-induced stomach lesions (ex. ulcers) when used as a pretreatment in animal models [30].

In small intestine grafts, glycine improves smooth muscle dysfunction after transplantation as well as reduces inflammation [31].

Glycine, but not L-arginine, is able to maintain intestinal wall integrity and mucosa in cancer treatment irradiation in animal models [32].

Glycine has protective effects against oxidative stress in intestinal cells in test tubes [33].

Glycine could potentially help prevent the formation of ulcers in response to stress or harmful chemicals, but human studies have been very limited.

6) Metabolic Disorders

5g glycine taken in the morning increased total insulin response in 12 healthy first-degree relatives of Type 2 diabetes patients [34].

Glycine is believed to help with diabetes and metabolic disorders [2].

Glycine intake decreases free fatty acids in blood, fat tissue cell size, and blood pressure in sucrose-fed rats [35].

Glycine reduces glycated hemoglobin (A1C), a risk factor associated with poor blood glucose management in patients with type 2 diabetes. The dose was 5g/d [36].

Glycine stimulates the secretion of a gut hormone (glucagon) that helps insulin to remove glucose from circulation [37].

Glycine helps patients with oxidative stress in the development of metabolic syndrome [38].

Glycine increases adiponectin, which may trigger weight loss in obese people, but this effect has only been observed in a cell study [39].

Glycine is considered important for metabolic health, but much of the research on this topic is limited to animals and cells.

7) Glucose Balance & Diabetes

Diabetic patients have 26% lower blood glycine levels than “normal” population [40].

Glycine helped 8 older, male HIV patients restore insulin sensitivity [41].

Glutathione synthesis was restored in patients with uncontrolled diabetes and hyperglycemia with glycine (+cysteine) added to their diet [42].

Glycine helps with lipid profiles in insulin-resistant patients (but not insulin resistance).

Glycine can help with positive glucose management by stimulating the production of Glucagon, a hormone which helps potentiate the action of insulin [37].

These early studies are promising, but larger and more robust human trials are needed.

People with diabetes appear to have lower blood glycine than the average, and glycine supplementation improved insulin sensitivity and glutathione synthesis in diabetic patients.

8) Heart Health

Glycine lowered systolic blood pressure in 60 patients with metabolic syndrome [38, 41].

In heart attack conditions (Post-ischaemic reperfusion) glycine prevented the death of heart muscle cells by inhibiting mitochondrial permeability in rats [43].

Glycine depletion within cells during a heart attack (hypoxia/reoxygenation) may make heart cells more vulnerable to cell death [43].

Glycine lowered blood pressure in patients with metabolic syndrome; glycine’s role in heart health has otherwise not yet been studied in humans.

9) Joint, Bone, and Muscle Strength

Glycine improved body composition and muscle strength in 8 older men with HIV [41].

Glycine protected against (peptidoglycan polysaccharide-induced) arthritis in animal studies [28].

Glycine combined with green tea benefits tendon recovery processes after tendinitis by better collagen bundling organization [44].

Glycine can potentially help in menopause because of its estrogen-like bone protective effects [45].

Glycine played a role in maintaining the health of mice suffering from osteoarthritis [45].

Glycine is believed to be important for joint, bone, and tissue strength. High-quality human research into this potential benefit is lacking.

Animal & Cell Research (Lacking Evidence)

No clinical evidence supports the use of glycine for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.

10) Inflammation

Glycine acts directly on inflammatory cells to suppress the activation of transcription factors, the formation of free radicals, and inflammatory cytokines [28].

Glycine reduces TNF-alpha and increases interleukin-10 [36].

Glycine can reduce TNF-receptor I levels, and raise interferon (IFN)-gamma levels in diabetic patients [36].

Glycine significantly inhibits NF-κB activation and IL-6 production in heart artery cells [46].

Glycine increases the anti-inflammatory IL-10 production in toxin-induced liver injury, increasing rat survival rates [47].

Glycine significantly improves toxin-exposed mice survival rates by lowering TLR4 and TNF-alpha and inhibiting Nf-kB [47].

Feeding rats diets high in glycine (5%) totally prevented death after exposure to an injection of a toxin (E Coli) by blunting TNF-alpha. Whereas 50% of the control group died within 24hrs [48].

In this same study, glycine fed rats who had liver damage and also injected with a toxin had an 83% survival rate, whereas the non-glycine control group had 0% rate of survival [48].

In mice fed with various types of sugar, TNF-alpha is significantly higher in mice fed fructose [49].

Glycine has protective properties against the harms of Fructose by its ability to prevent the release of inflammatory cytokines (TNF-α, IL-6) release with fructose exposure [50].

Glycine plays an important role in reducing oxidative stress in the body [38].

As a precursor to glutathione, glycine can restore previously lowered levels of glutathione [42, 51].

Glycine is sometimes recommended to the elderly because glutathione levels naturally fall with age [52].

Animal and cell research indicates that glycine is important for reducing inflammation and oxidative stress.

11) Liver Health

Glycine prevents lactate dehydrogenase leakage (a cell death indicator) in rat liver cells in test tubes [53].

In rats with alcohol poisoning, feeding glycine reduced accumulation of cholesterol, phospholipids, free fatty acids and triglycerides in blood circulation, liver, and brain, ultimately reversing liver disorder associated with fat accumulation [19].

In rats deficient in choline and methionine, glycine supplementation prevents liver injury [54].

Glycine reduced liver damage and decreases mortality rates in rats suffering from a serious bacterial infection (sepsis) [55].

Glycine was able to maintain Vitamin D blood levels in animals models with induced liver disease (bile duct ligation), and also slow liver damage [56, 57]

Supplementation of glycine for five days in animal models prior to complete or partial liver donation significantly inhibited liver injury and liver-related enzymes [58].

Glycine maintains mitochondrial activity and bile composition in liver injury in animals [59].

In animals, glycine supplementation has improved liver health and bile composition and prevented complications from liver injury.

12) Alcohol Absorption

Blood alcohol levels were significantly lower in animals which had consumed glycine prior to intoxication over controls who had not [60].

Glycine reduced the rate at which the stomachs of mice absorbed alcohol and emptied into the intestine [61].

13) Kidney Health

Kidney tubes (proximal tubules) are resistant to oxygen deprivation damage if glycine is present in the test tube. This has only been observed in an isolated tissue study, and studies in animals and humans are lacking, so we can’t say what the implication is for kidney health in a living system [62].

14) Oral Health

In rat models, supplementation with 4% glycine caused a 65.7% reduction of cavity occurrence. This has not been investigated in humans [29].

15) Thyroid Hormones

Glycine might also increase the conversion of T4 to T3 in the liver, but this effect has only been studied in fish so far. It is unclear whether or how much this result might apply to human livers [63].

Supplementing With Glycine

Dosage

Note that there is no safe and effective dose because no sufficiently powerful and specific study has been conducted to determine one. That being said, many human trials have safely used doses between 1 g per day (for supporting brain health after a stroke) to over 50 g (for schizophrenia).

Most Americans get between 1.5 and 3 g of glycine from food, and our bodies produce another 3 g or so.

Many commercial supplements come in 1 g capsules or in free powder that can be scooped into shakes or other fluids.

Side Effects of Glycine

Slight sedation is a possible side effect of taking Glycine [21]. Some practitioners recommend taking it in the evening for this reason.

Potential Downsides of Glycine

In a Japanese study of nearly 30,000 patients, the risk of dying after stroke may be increased by meat consumption. The scientists pointed out a correlation between glycine intake and mortality from stroke, though they did not suggest a reason for this link [64].

Glycine is not recommended to take while suffering from diarrhea. It may worsen the condition and lead to poor rehydration [65].

Top Foods with The Highest Glycine Content

You can get a good amount of glycine from glycine, collagen or gelatin.

A list of foods high with glycine:

  • Gelatin
  • Whitefish
  • Soy Protein Isolate
  • Chicken
  • Turkey
  • Pork
  • Beef

Collagen contains 22 – 30% glycine. Adding 1 – 2 tbsp a day to a breakfast smoothie will give you an additional 2.5 – 3.5g glycine per Tbls.

Takeaway

Glycine is a semi-essential amino acid, meaning that the human body can produce some on its own, though some must also be consumed in food. The smallest of the amino acids, it is important for the production of many proteins and compounds, including DNA and RNA.

Glycine supplementation may prove useful for diabetic ulcers, schizophrenia, and stroke recovery. Other human studies suggest a potential benefit for other areas of metabolic and mental health, including insulin resistance, insomnia, and sleep disorders.

The richest dietary sources of glycine include gelatin, fish, and all types of meat. Glycine is also available as a dietary supplement.

About the Author

Puya Yazdi

Puya Yazdi

MD
Dr. Puya Yazdi is a physician-scientist with 14+ years of experience in clinical medicine, life sciences, biotechnology, and nutraceuticals.
As a physician-scientist with expertise in genomics, biotechnology, and nutraceuticals, he has made it his mission to bring precision medicine to the bedside and help transform healthcare in the 21st century.He received his undergraduate education at the University of California at Irvine, a Medical Doctorate from the University of Southern California, and was a Resident Physician at Stanford University. He then proceeded to serve as a Clinical Fellow of The California Institute of Regenerative Medicine at The University of California at Irvine, where he conducted research of stem cells, epigenetics, and genomics. He was also a Medical Director for Cyvex Nutrition before serving as president of Systomic Health, a biotechnology consulting agency, where he served as an expert on genomics and other high-throughput technologies. His previous clients include Allergan, Caladrius Biosciences, and Omega Protein. He has a history of peer-reviewed publications, intellectual property discoveries (patents, etc.), clinical trial design, and a thorough knowledge of the regulatory landscape in biotechnology.He is leading our entire scientific and medical team in order to ensure accuracy and scientific validity of our content and products.

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