Glycine is gaining increasing attention in the world of dietary supplements and healthy nutrition. This simple amino acid, found both in natural foods and as a dietary supplement, is essential for many functions in the body. Glycine is particularly valued for its positive effects on sleep, brain function, and muscle recovery. In this article, we'll explain everything you need to know about glycine, its benefits and uses, as well as its effects on the body and potential side effects.

What is glycine?

Glycine is a non-essential amino acid, meaning the body can produce it itself. Nevertheless, it is essential for many important bodily functions. Glycine is the smallest and simplest building block of proteins and plays a crucial role in the synthesis of collagen, creatine, and hemoglobin. It also serves as a neurotransmitter in the brain, where it has a calming and sleep-inducing effect [1].

Where does glycine come from?

Glycine occurs naturally in animal foods such as meat, fish, and gelatin. It is present in large quantities in bone broth and collagen. The body can also synthesize glycine from other amino acids such as serine and threonine. Glycine is often offered as a dietary supplement, particularly in powder or capsule form [2].

How is glycine produced?

Glycine can be obtained from natural sources or produced synthetically. Industrial production is usually achieved through chemical synthesis, using acetic acid as the starting material. Glycine is often used in its pure form in dietary supplements to specifically support its health benefits [3].

Health benefits of glycine

Glycine and sleep

One of the most well-known benefits of glycine is its effect on sleep. Glycine helps calm the body and brain by acting as an inhibitory neurotransmitter. It lowers body temperature, thus promoting sleep onset. Studies have shown that taking glycine before bedtime improves sleep quality, makes it easier to fall asleep, and increases the time spent in deep sleep [4]. Glycine is therefore particularly useful for people who suffer from insomnia or restless sleep.

Glycine and brain function

Glycine also plays an important role in brain function. It acts as a neurotransmitter that regulates signals between nerve cells. Glycine acts as an inhibitor and can reduce excessive neuronal activity, which can lead to improved cognitive function and mental clarity [5]. Glycine also supports the production of glutathione, a powerful antioxidant that protects the brain from oxidative stress.

Glycine and muscle regeneration

Glycine is necessary for the synthesis of creatine and collagen, both of which play an important role in muscle recovery. By promoting protein synthesis, glycine helps the body repair damaged muscle cells and build new tissue [6]. Many athletes and fitness enthusiasts therefore value glycine as a supplement to promote recovery after intense training.

Glycine and metabolic health

Glycine supports the body in regulating blood sugar levels by improving insulin sensitivity. This can help reduce blood sugar fluctuations and lower the risk of metabolic disorders such as type 2 diabetes [7]. Combined with a healthy diet, glycine can thus contribute to better metabolic health.

How does glycine work in the body?

Glycine functions in the body in several ways. As an amino acid, it is a building block for proteins and plays a key role in the formation of collagen, which is essential for skin, hair, nails, and joints. It also acts as a neurotransmitter in the central nervous system, inhibiting overactive nerve cells. This action helps calm the nervous system, reduce stress, and promote sleep. Glycine also contributes to the formation of glutathione, a powerful antioxidant that protects cells from oxidative stress [8].

Recommended dosage and use of Glycine

What is the recommended dosage?

The recommended dosage of glycine depends on the desired effects. To improve sleep and relaxation, the usual dose is 3 to 5 grams per day, taken approximately 30 to 60 minutes before bedtime [9]. To support muscle recovery and metabolism, glycine can also be taken in smaller doses of 1 to 3 grams spread throughout the day.

When should you take glycine?

Glycine can be taken at different times depending on the intended purpose. To improve sleep quality, it should be taken shortly before bedtime. For muscle building and recovery, glycine can also be taken after training or in conjunction with meals to support protein metabolism [10].

Side effects and safety of glycine

Is glycine safe?

Glycine is generally considered very safe when taken in recommended doses. It is a naturally occurring amino acid that the body produces and is also found in many foods. No serious side effects are known when glycine is consumed in normal amounts [11]. However, people with certain pre-existing medical conditions or who regularly take medication should consult a doctor before taking glycine.

What are the side effects of glycine?

In rare cases, mild side effects such as gastrointestinal discomfort, nausea, or mild drowsiness may occur when taking glycine. These effects are generally mild and usually only occur at very high doses. It is recommended to increase the dosage slowly to allow the body to adjust to the effects and avoid potential side effects [12].

Glycine compared to other ingredients

Glycine vs. L-Theanine

Both glycine and L-theanine have calming and sleep-promoting properties, but they work in different ways. While glycine acts as an inhibitory neurotransmitter and lowers body temperature, L-theanine increases the production of alpha waves in the brain, leading to a state of relaxed alertness. Both amino acids can work synergistically to reduce stress and improve sleep [13].

Glycine vs. Glutamine

Glycine and glutamine are both non-essential amino acids, but they have different functions. While glycine primarily contributes to calming and recovery, glutamine is especially important for the immune system and gut health. Both amino acids can be used in combination to promote overall health [14].

Natural sources of glycine

Glycine occurs naturally in protein-rich foods such as meat, fish, eggs, and dairy products. Particularly high concentrations are found in collagen and gelatin, which are found in bone broth and meat-rich dishes. Plant sources such as legumes and soy also contain small amounts of glycine, although in significantly lower concentrations than animal products [15].

Final Thoughts on Glycine

Glycine is a versatile amino acid that plays a vital role in health. Whether it's promoting sleep, supporting brain function, or improving muscle recovery, glycine offers numerous health benefits and is a safe and effective supplement for many people. Thanks to its calming effect on the nervous system and its role in metabolism, glycine can be a valuable addition to your daily routine to reduce stress, improve sleep, and promote overall health.