Glycine: Benefits, Side Effects, Best Time to Take It & More (2024)

Since glycine is a non-essential amino acid, you do not need to consume it to survive. However, this amino acid still plays an important role in human health.

Glycine is a component of collagen, which is needed for proper joint health and other collagen-related effects. About 25% of collagen by weight is glycine. Unfortunately, supplemental glycine doesn’t seem to improve joint health.

This amino acid acts as a precursor to a variety of molecules, such as creatine.

Glycine can also act as a neurotransmitter. It can have both stimulating and sedative effects.

• Improved sleep quality – Multiple studies show that glycine supplements (about 3 grams taken an hour before bed) can increase sleep quality on the following night.
• Reducing the negative effects of methionine – These two amino acids have to be kept in balance as too much of one (methionine, in particular) without enough of the other can cause unnecessary harm. For every gram of methionine, you need to consume at least half a gram of glycine if you wish to prevent side effects related to too much methionine. For optimal health, try to get about 1 gram of glycine for every gram of methionine.

• Improved cognition – This effect is secondary to improving sleep quality. In people who sleep well without the supplement and aren’t schizophrenics, glycine is unlikely to have a notable effect on cognition.
• Reduced fatigue – This benefit is also secondary to improving sleep quality and doesn’t seem to apply to people who sleep just as well without supplemental glycine.
• Reduced symptoms of schizophrenia – Glycine can reduce symptoms of schizophrenia when taken at extremely high doses (800+ mg/kg/d). This dose seems too impractical and may not be safe to take in the long term.
• Improved insulin sensitivity – Low serum glycine levels are associated with insulin resistance. However, this is likely because insulin resistance leads to a depletion in glycine.

• Amino acid imbalance – Essential and non-essential amino acids should be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects if there isn’t enough of another amino acid. For example, this principle applies to glycine and methionine, lysine and arginine, and the BCAA trio. There are many other proven and unproven examples. Food or a protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a particular amino acid/s.
• Toxicity – While acute toxicity has never been reported, taking high amounts of glycine could lead to chronic toxicity and cause some health problems. To prevent chronic toxicity, it is best to stay below 6 grams a day unless you have a great reason to take more.
• Contamination– Contaminated supplements are uncommon in the USA and other well-regulated countries. However, if you wish to buy products from China, India, or other countries without strict regulations, beware that the supplements may be contaminated. Either way, you need to choose the brand you order from wisely. It is highly recommended to check the certificates or read through some reviews for the specific product before you buy it. The FDA (Food and Drug Administration) has the power to regulate dietary supplements but can only do so after they have been on the market for a while. That’s because supplement companies are not obligated to announce to the FDA when releasing a new product on the market. The FDA has to discover the product and test it for potential impurities, which can take a lot of time. During that time, the supplement can be sold on the market even if it’s impure. Also, supplement companies can change their manufacturers without announcing it to the FDA.

• get enough glycine from food
• experience a severe adverse reaction after taking the amino acid
• are on a tight supplement budget (since there are more cost-effective supplements on the market for most people)

• eat high amounts of methionine (for optimal health, you should get at least half a gram (preferably a full gram) of glycine for every gram of methionine)
• have difficulty falling asleep
• consume very little protein (less than 0.3 grams/pound of body weight)
• suffer from insulin resistance
• are pregnant (pregnant women need more glycine)

Since this amino acid can be found in food or synthesized in the body, you may already get sufficient amounts without taking it as a supplement. About 0.36 grams of protein/pound of body weight should generally be enough to prevent any symptom deficiency.

If you plan to take glycine as a supplement, 3-5 grams appears to be the best daily target for most people. This amount should provide most of the benefits without meaningful side effects.

Some people may benefit from doses higher than 5 grams. These include schizophrenics, carnivores with a high methionine intake, and people with difficulty sleeping.

Glycine can reduce symptoms of schizophrenia when taken at extremely high doses (800+ mg/kg/d). This dose seems too impractical and may not be safe to take in the long term.

Beware that for optimal health you should get at least half a gram (preferably a full gram) of glycine for every gram of methionine.

The upper safety limit for glycine is not well-established. To stay on the safe side, don’t take more than 6 grams daily unless you have a great reason to do so. Higher amounts may cause problems if you take the supplement for a prolonged period.

An average diet provides about 2 grams of glycine.

Glycine is found in all whole foods that contain dietary protein.

The amount of glycine per gram of protein varies from food to food but a general rule of thumb is that the more protein you eat, the more glycine you are getting from food.

Beware that for optimal health you should get at least half a gram (preferably a full gram) of glycine for every gram of methionine.

This is generally the ratio people get from their diet. However, people who eat lots of muscle meat (the richest source of methionine) without getting enough glycine can throw this ratio off balance. This can cause long-term negative effects on their health.

The easiest way to find out exactly how much glycine, methionine, or other amino acids you are getting from food is with Cronometer.com. This free app allows you to track all vitamins, minerals, and more.

Like most other amino acids, glycine is water-soluble, so you don’t have to take it with food to absorb it well. Taking the supplement with food is better if it causes stomach upset when you take it on an empty stomach.

To maximize the benefits, take glycine before falling asleep. One of the main benefits of the supplement is improving sleep quality.

If you practice time-restricted eating, take this amino acid during your eating window to guarantee it won’t break your fast.

Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.

• Methionine
  For every gram of methionine, you need to consume at least half a gram of glycine if you wish to prevent side effects related to too much methionine. For optimal health, try to get about 1 gram of glycine for every gram of methionine.
• Other amino acids
  Essential and non-essential amino acids should be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects if there isn’t enough of another amino acid. For example, this principle applies to glycine and methionine, lysine and arginine, and the BCAA trio. There are many other proven and unproven examples. Food or a protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a particular amino acid/s.
• Vitamin B3
  Vitamin B3 supplements (such as niacinamide, nicotinic acid, NR, and NMN) can deplete levels of TMG (trimethylglycine) in the body. If you’re taking nicotinic acid, combine it with half the dose of glycine to prevent liver toxicity. For example, for 1000 mg of nicotinic acid, take 500 mg of glycine. With the other forms of vitamin B3, you don’t need to worry about glycine as much.
• Clozapine
  Clozapine (Clozaril) is used to help treat schizophrenia. Glycine may decrease the effects of Clozapine and thus shouldn’t be taken with the drug.

Amazon is the best option for ordering glycine supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.

Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.

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