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Glycine: The Underrated Amino Acid That Could Improve Your Sleep, Recovery, and Overall Health

Cheap, well tolerated and quietly useful — what the sleep, collagen and glutathione research actually supports, plus our five editorial picks.

These are SupplementDecider editorial picks. Rankings are based on overall value, brand reputation, product format, and practical usefulness. They are not claims that SupplementDecider independently laboratory-tested any product, and no ranking position is for sale.

For years, glycine has quietly remained one of the most overlooked supplements in nutrition. Unlike flashy “miracle” ingredients, glycine is a simple amino acid naturally found in collagen, meat, fish, eggs, and other protein-rich foods. Yet research suggests it may support sleep quality, connective-tissue health, recovery, and normal nervous-system function.

The good news is that glycine is also one of the least expensive supplements available. Because supplemental glycine is generally sold as the same free-form amino acid, consumers often gain more by comparing manufacturing quality, serving size, convenience, and price than by paying for elaborate marketing.

What is glycine?

Glycine is the smallest amino acid in the human body. The body can make it, so it is traditionally called nonessential. However, some researchers consider it conditionally essential because the amount produced may not always meet the body’s needs during aging, illness, heavy training, injury, or increased collagen production.

Glycine contributes to collagen, glutathione production, creatine synthesis, bile acids, heme, and normal nervous-system signaling. It also acts as an inhibitory neurotransmitter in parts of the brain and spinal cord.

Potential benefits of glycine

Sleep support

Small clinical studies have used about 3 grams of glycine before bedtime. Participants reported improvements in sleep quality, falling asleep, or next-day fatigue. The evidence is promising but still based on relatively small studies.

Collagen and connective tissue

Glycine is a major building block of collagen, the principal structural protein in skin, joints, cartilage, tendons, ligaments, and bone. Glycine supplementation is not guaranteed to rebuild damaged joints, but adequate glycine intake helps provide material the body uses to make collagen.

Antioxidant defenses

Glycine is one of three amino acids needed to produce glutathione, a major antioxidant made by the body. Glycine may therefore help support normal antioxidant defenses, especially when combined with adequate cysteine and glutamate.

Exercise and recovery

Because glycine participates in creatine and collagen production, it may support recovery and connective-tissue maintenance. Direct evidence that glycine alone significantly improves athletic performance remains limited.

Blood pressure and metabolic health

Some research has suggested possible cardiovascular or metabolic benefits in selected populations, but glycine is not an established treatment for high blood pressure, diabetes, or cardiovascular disease. It must not replace prescribed medication or medical care.

Brain and mental-health research

Very high doses have been studied in certain psychiatric conditions because glycine affects NMDA receptors. These research doses are far above ordinary supplement use and should never be attempted without specialist supervision. Evidence for depression, tinnitus, and other neurological conditions remains inadequate.

Powder vs. capsules

Powder is generally the best value for anyone taking several grams per day. It is easy to mix with water and has a naturally mildly sweet taste. Capsules are more convenient for travel and eliminate measuring, but reaching a 3-gram serving may require several large capsules.

SupplementDecider’s top five glycine picks

Editorial recommendations based on overall value, brand reputation, convenience, product format, and practical usefulness.

  1. 1Best overall9.8/105.0

    NOW Foods Glycine

    NOW Foods combines strong brand recognition, broad availability, powder and capsule choices, and competitive pricing. It is the most practical all-around option for many shoppers.

    Best for: Shoppers seeking dependable quality and value without paying a premium.

  2. 2Best premium choice9.6/105.0

    Thorne Glycine

    Thorne is widely recognized for professional-grade supplements and careful manufacturing standards. Its glycine costs more than budget products, but it appeals to consumers who place a high priority on brand reputation and practitioner familiarity.

    Best for: Consumers who prefer a premium supplement company and do not mind paying more.

  3. 3Best capsule for healthy-aging shoppers9.5/104.5

    Life Extension Glycine

    Life Extension has a long-standing focus on evidence-informed nutrition and healthy aging. Its 1,000-milligram capsules provide a simple way to adjust intake in one-gram increments.

    Best for: People who prefer capsules and already trust Life Extension products.

  4. 4Best budget powder9.4/104.5

    BulkSupplements Glycine

    BulkSupplements is a strong option for buyers who want plain glycine powder in larger quantities at a low cost per serving. Powder is especially practical for the commonly studied 3-gram bedtime amount.

    Best for: Regular users and cost-conscious shoppers comfortable measuring powder.

  5. 5Best capsule value9.2/104.0

    Double Wood Supplements Glycine

    Double Wood offers a straightforward capsule option with a large bottle size. It may suit consumers who want capsules without moving into the highest-priced premium tier.

    Best for: Buyers prioritizing capsule convenience and long-term supply.

How much glycine is commonly taken?

A frequently studied amount for sleep is 3 grams roughly 30 to 60 minutes before bedtime.

General supplement products often provide between 1 and 3 grams per serving. Much larger research doses should not be self-administered.

Start with the lowest practical amount and assess tolerance. Follow the product label unless a qualified healthcare professional recommends otherwise.

Food sources of glycine

Glycine occurs naturally in meat, poultry, fish, eggs, dairy products, legumes, seeds, gelatin, collagen, bone broth, skin, and connective tissue. People eating a balanced protein-rich diet already obtain glycine from food, although the exact amount varies considerably.

Safety and side effects

Glycine is generally well tolerated at ordinary supplemental amounts. Possible effects include nausea, stomach discomfort, loose stools, or sleepiness. Very high doses are more likely to cause gastrointestinal problems.

Consult a healthcare professional before taking glycine if you are pregnant or breastfeeding, have kidney or liver disease, take seizure medication, take antipsychotic medication — especially clozapine — or use blood-pressure-lowering drugs.

Glycine may lower blood pressure in some people, so anyone who experiences dizziness, weakness, faintness, or an unusually low reading should stop and seek medical advice.

Final verdict

Glycine is not a miracle cure, but it may be one of the most practical and affordable amino-acid supplements available. The strongest everyday case is sleep support, while its biological roles in collagen and glutathione make it scientifically interesting for recovery and healthy aging.

For most buyers, NOW Foods offers the best overall balance. Thorne is the premium choice, Life Extension is a strong capsule option, BulkSupplements provides excellent powder value, and Double Wood offers convenient capsules at a competitive level.

Medical disclaimer

This article is for educational purposes only and is not medical advice. Dietary supplements are not intended to diagnose, treat, cure, or prevent disease. Consult a qualified healthcare professional before starting a supplement, especially if you have a medical condition or take prescription medication.

Independence

SupplementDecider does not sell supplements and accepts no payment for evidence ratings, rankings or verdicts.