Glycine as a therapeutic supplement
Glycine is a nonessential amino acid that plays a crucial role in the human body, functioning as a building block for proteins. It has been studied mainly for its potential therapeutic effects in various health conditions, most notably schizophrenia. Some research suggests that glycine may enhance the efficacy of certain antipsychotic medications, particularly for addressing the negative symptoms of schizophrenia, although its interaction with clozapine appears to be less favorable.
Additionally, glycine is being explored for other therapeutic uses, including anxiety reduction, sleep improvement, and metabolic health support, particularly in diabetes management. Preliminary studies indicate that glycine might also aid in limiting brain damage after strokes and enhancing wound healing. While glycine is generally considered safe, especially at typical dietary levels, high doses for therapeutic purposes should be approached with caution and under medical supervision due to potential risks, including interactions with medications. Overall, while the promise of glycine as a therapeutic supplement is recognized, further research is needed to substantiate its efficacy and safety across various health conditions.
Glycine as a therapeutic supplement
- DEFINITION: Natural substance of the human body used as a supplement to treat specific health conditions.
- PRINCIPAL PROPOSED USE: Schizophrenia
- OTHER PROPOSED USES: Anxiety, cancer prevention, diabetes, enhancing memory and mental function, epilepsy, heart health, immune support, kidney protection, liver protection, metabolic health, prostate enlargement, sleep, sports performance, strokes, wound healing
Overview
Glycine is the simplest of the twenty amino acids used as building blocks to make proteins for the body. It works in concert with glutamine, a substance that plays a significant role in brain function. Glycine has shown some promise as an aid in the treatment of schizophrenia and may have other uses related to the brain as well, such as enhancing mental function, amongst myriad other health claims.
Requirements and Sources
The body makes glycine using another amino acid, serine. Because one can manufacture glycine, one does not have to consume any, so it is called a nonessential amino acid. Most people get about 2 grams (g) of glycine daily from regular foods. This dietary glycine comes mostly from high-protein foods like meat, fish, dairy products, and legumes. However, much larger amounts than are commonly consumed for treating certain disease conditions have been advocated; such high doses can be obtained only by taking supplements.
Therapeutic Dosages
Dosages of oral glycine used in clinical trials for therapeutic purposes range from 2 to 60 g daily.
Therapeutic Uses
Several studies have evaluated glycine as a supportive treatment for schizophrenia. According to some of these studies, high doses of glycine (15 to 60 g daily) might augment the effectiveness of medications used for this condition. The notable exception is clozapine (Clozaril); one study suggests that glycine may decrease the effectiveness of this drug.
One large double-blind study suggests that low doses of glycine may help limit the spreading of brain damage that occurs during stroke. However, there are also theoretical concerns that glycine could increase such damage, so one should not try this treatment except under physician supervision. Glycine may have additional benefits for mental health, as early studies have shown it can improve the quality of sleep, and its benefits for reducing anxiety are being studied. Another small study weakly suggests that glycine may enhance memory and mental function.
A small double-blind study found evidence that glycine may help improve long-term blood sugar control in people with type 2 diabetes. Glycine may also be beneficial for other metabolic disorders, such as fatty liver disease. Glycine alone and in combination with other amino acids has shown some promise for enhancing wound healing.
Animal studies suggest that dietary glycine may protect against chemically induced damage to the liver or kidneys. Other studies in laboratory animals suggest that dietary glycine may prevent tumor formation and growth in the livers of mice and rats. However, it is too early to say whether glycine has cancer-preventive effects in humans.
Manufacturers advertising glycine supplements have made several additional claims, including preventing epileptic seizures, reducing stomach acid, reducing multiple sclerosis symptoms, boosting the immune system, and calming the mind. It is also proposed as a sports supplement, which is said to work in this capacity by increasing the release of human growth hormone (HGH). No scientific evidence exists proving that glycine works for any of these purposes. A 2024 review of studies determined not enough scientific evidence existed to support claims of muscle growth and recovery following exercise. Because it has a sweet taste, glycine has also been recommended as a sugar substitute for people with diabetes.
Scientific Evidence
Schizophrenia. Glycine might enhance the effectiveness of drugs used for schizophrenia, especially those in the older phenothiazine category. It has also shown equivocal promise for enhancing the effectiveness of the drugs risperidone and olanzapine. However, it may not be helpful for people using clozapine.
Phenothiazine drugs are most effective for the “positive” symptoms of schizophrenia, such as hallucinations and delusions. (Such symptoms are called positive because they indicate the presence of abnormal mental functions rather than the absence of normal mental functions.) In general, however, these medications are less helpful for the “negative” symptoms of schizophrenia, such as apathy, depression, and social withdrawal. Glycine might be of benefit here.
A double-blind, placebo-controlled trial enrolled twenty-two participants who continued to experience negative symptoms of schizophrenia despite standard therapy. The results showed that the use of glycine significantly improved negative symptoms. In addition, glycine also appeared to reduce some of the side effects caused by the prescription drugs. No changes were seen in positive symptoms (for instance, hallucinations). Still, it is not possible to tell whether that is because prescription medications were already controlling these symptoms or if glycine simply has no effect on those particular symptoms of schizophrenia.
Double-blind, placebo-controlled clinical trials of glycine together with standard drugs for schizophrenia also found it to be helpful for negative symptoms. These studies used very small groups (from twelve to eighteen people), so much larger trials are still needed to verify glycine’s effectiveness. The trials were conducted before atypical antipsychotics were widely available. These drugs cause fewer side effects and also provide benefits for the negative symptoms of schizophrenia along with the positive. One study found that glycine augmented the effectiveness of two of these drugs: olanzapine and risperidone. However, another study suggests that adding glycine to the atypical antipsychotic clozapine may not be a good idea. In this study, glycine was found to reduce the benefits of clozapine. Other double-blind, placebo-controlled trials of glycine and clozapine simply failed to find benefit. Another recent study, not specifically limited to clozapine, failed to find glycine benefits.
Stroke. Glycine’s potential usefulness for treating individuals who have undergone strokes was investigated in a double-blind, placebo-controlled study with two hundred participants. The results suggest that glycine can protect against the spreading damage to the brain that usually follows a stroke. Participants were given either 1 to 2 g of glycine sublingually (dissolved under the tongue) or a placebo treatment for a period of five days. The results suggest that glycine can prevent neural damage. This appears to be an impressive result, but further research is necessary.
Although other researchers using glycine for brain disorders have reported that such small doses of glycine would not be sufficient to cross the blood-brain barrier, measurements of amino acids in the cerebrospinal fluid during the above study suggest that it did enter the brain. However, there are potential concerns that high-dose glycine could increase stroke damage.
As the twenty-first century progressed, scientific study into the health benefits of glycine continued. As previously discussed, human studies were conducted on glycine for sleep, exercise performance, and metabolic health with varying conclusions. Still, because many of the proposed therapeutic health benefits of glycine have only been seen in laboratory and animal studies, increased scientific study is needed.
Safety Issues
No serious adverse effects from using glycine have been reported, even at doses as high as 60 g per day. One participant in the twenty-two-person trial described above developed stomach upset and vomiting, but it ceased when the glycine was discontinued.
In contradiction to the study on strokes mentioned above, theoretical concerns have been raised that suggest glycine might increase brain injury in strokes. Drugs that block glycine have been investigated as treatments to limit stroke damage. However, the authors of the study on strokes described above make an argument suggesting that glycine's overall effect is protective. Until this controversy is settled, prudence suggests not using glycine following a stroke except on the advice of a physician.
In addition, as noted above, it is possible that use of glycine could reduce the benefits of clozapine. Maximum safe doses for young children, pregnant or nursing women, or people with liver or kidney disease are not known. Persons taking clozapine should not take glycine except under the supervision of a physician.
Bibliography
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Diaz, P., et al. "Double-Blind, Placebo-Controlled, Crossover Trial of Clozapine Plus Glycine in Refractory Schizophrenia Negative Results." Journal of Clinical Psychopharmacology, vol. 25, 2005, pp. 277-278.
Myhre, James, and Dennis Sifris. "Glycine: Benefits, Side Effects, and Risks." Verywell Health, 30 Aug. 2024, www.verywellhealth.com/glycine-overview-4583816. Accessed 8 Oct. 2024.
Heresco-Levy, U., et al. "High-Dose Glycine Added to Olanzapine and Risperidone for the Treatment of Schizophrenia." Biological Psychiatry, vol. 55, 2004, pp. 165-171.
Javitt, D. C., et al. "Reversal of Phencyclidine-Induced Effects by Glycine and Glycine Transport Inhibitors." Biological Psychiatry, vol. 45, 1999, pp. 668-679.
Patricia, Rosa, et al. "An Update of the Promise of Glycine Supplementation for Enhancing Physical Performance and Recovery." Sports, vol. 12, no. 10, 2024, p. 265, doi.org/10.3390/sports12100265. Accessed 8 Oct. 2024.
Zhou, X., et al. "Glycine Protects Against High Sucrose and High Fat-Induced Non-Alcoholic Steatohepatitis in Rats." Oncotarget, 2016, www.oncotarget.com/article/12831/text/. Accessed 8 Oct. 2024.