Glycine

Glycine is an amino acid that the body uses to produce proteins that it needs for growth and maintenance of body tissue and for the production of important substances such as hormones and enzymes. The body can produce glycine itself from other amino acids, but glycine can also be found in protein-rich foods and is also available as a supplement. Aside from being a component of body proteins, glycine has a number of impressive health benefits and functions, which we will take a closer look at in this article.

Glycine is needed for the production of a powerful antioxidant

Glycine is one of the three amino acids required by the body to produce glutathione - a powerful antioxidant that helps protect the body's cells from oxidative damage caused by free radicals, which is believed to be at the root of many diseases (1). Without adequate amounts of glycine, the body cannot produce enough glutathione, which can negatively impact the body's ability to cope with oxidative stress (2, 3). As glutathione levels decrease with age, ensuring that you consume more glycine as you age may have positive effects on your health. Summary: Glycine helps the body produce glutathione, an important antioxidant that protects the body from cell damage.

Glycine is a component of creatine

Glycine is one of the three amino acids the body needs to make creatine. Creatine provides the muscles with energy for quick and short bursts of high-intensity activities such as weightlifting or sprinting. Creatine has been shown to increase muscle mass, strength and speed in combination with resistance training (4, 5, 6). Creatine has also been studied for its positive effects on bone health, brain function and neurological diseases such as Parkinson's and Alzheimer's (7, 8, 9). Although the body can produce creatine itself and creatine can also be obtained from food, an insufficient intake of glycine can reduce the amount of creatine produced by the body.

Summary: Glycine is a component of creatine - a compound that provides energy to muscles and has been linked to numerous other health benefits such as better bone health and brain function.

Glycine is the primary amino acid in collagen

Collagen is a structural protein that contains a large amount of glycine. In fact, one out of every three or four amino acids in collagen is glycine 11). Collagen is the most abundant protein in the body, providing stability to muscles, skin, joint cartilage, blood, bones and ligaments. Collagen supplementation has been shown to provide benefits for skin health, relieve joint pain and prevent bone loss (12, 13, 14). For this reason, it is important to consume enough glycine to support the body's collagen production.

Summary: Glycine is the most abundant amino acid in collagen. Collagen is a structural protein that has many benefits including skin, joints and bones.

Glycine could improve sleep quality

Many people struggle to get enough good, restful sleep at night, either having trouble falling asleep or staying asleep. While there are many ways to improve sleep quality, including avoiding caffeinated drinks later in the day and avoiding bright light during the last few hours before bedtime, glycine may also be helpful. Glycine has a calming effect on the brain and may help you fall asleep and stay asleep faster by lowering your body's core temperature (15, 16). Research conducted with subjects suffering from sleep problems has shown that taking 3 grams of glycine before bedtime shortens the time it takes to fall asleep, improves sleep quality, reduces daytime sleepiness and improves cognition (17, 18). For this reason, glycine may be a good alternative to prescription sleep aids when it comes to improving sleep quality and reducing daytime sleepiness.

Summary: Glycine may promote good sleep and improve sleep quality through its calming effects on the brain and its ability to lower the body's core temperature.

Glycine may protect the liver from alcohol-induced damage

Too much alcohol can have harmful effects on the body, particularly the liver. As far as the liver is concerned, there are three primary types of alcohol-induced damage (19):

An alcohol-induced fatty liver: an accumulation of fat in the liver, which leads to an enlargement of the liver.
Alcohol-induced hepatitis: A form of hepatitis caused by inflammation of the liver resulting from prolonged, excessive alcohol consumption.
Alcohol-induced cirrhosis: This is the final stage of alcohol-related liver disease, which occurs when the liver cells are damaged and replaced by scar tissue.

Interestingly, scientific research suggests that glycine may reduce the damaging effects of alcohol on the liver by preventing inflammation. Glycine has been shown to reduce blood alcohol concentrations in alcohol-fed rats by stimulating the metabolism of alcohol in the stomach rather than the liver, preventing the development of fatty liver and alcohol-induced cirrhosis (20). In addition, glycine may also help repair liver damage caused by excessive alcohol consumption in animals. While moderate alcohol-induced liver damage can be reversed by abstinence, glycine could improve the regeneration process. In a study of rats with alcohol-induced liver damage, liver cell health returned to baseline 30% faster compared to the placebo group when the animals followed a glycine-rich diet for two weeks (21). Despite these promising results, studies on the effects of glycine on alcohol-induced liver damage have so far been limited to animals and cannot be directly translated to humans (22, 23, 24).

Summary: A glycine-rich diet can reverse alcohol-induced liver damage in rats. The corresponding effects in humans are not yet known.

Glycine could protect the heart

Increasing evidence suggests that glycine may offer protection against heart disease. It prevents the accumulation of a compound that in high amounts is associated with arteriosclerosis - the hardening and narrowing of the arteries (25, 26, 27, 28). Glycine may also improve the body's ability to produce nitric oxide (29). Nitric oxide is an important molecule that can increase blood flow and lower blood pressure. In a 7.4-year observational study of over 4,100 people suffering from chest pain, higher glycine levels were associated with a lower risk of heart disease and heart attacks (28). After factoring out the effect of cholesterol-lowering medications, researchers also observed more beneficial blood cholesterol levels in those who had higher glycerol levels (28). In addition, studies have shown that glycine was able to reduce several risk factors for heart disease in rats fed a high-sugar diet (29). Eating too much added sugar can increase blood pressure and blood lipid levels and promote the buildup of dangerous belly fat - all factors that can promote heart disease (30). However, although these study results on the effects of glycine on heart disease risk are promising, further human studies are needed before glycine use can be recommended for this purpose (31).

Summary: Glycine could reduce risk factors for heart disease by preventing the accumulation of a molecule associated with heart disease and by improving the body's ability to utilize nitric oxide.

Glycine could help people with type 2 diabetes

Type 2 diabetes can lead to low glycine levels. Diabetes is a disease characterized by impaired insulin secretion and insulin action, which means that the body does not produce enough insulin or that it does not respond properly to the insulin it does produce (32). Insulin lowers blood glucose levels by signaling cells to take up sugar from the blood and use it for energy or storage. Interestingly, it has been observed that glycine can increase the insulin response in people without diabetes. For this reason, it is thought that glycine supplements may also improve impaired insulin response in people with type 2 diabetes (11, 33, 34). Higher glycine levels are associated with a reduced risk of type 2 diabetes - even after all other factors, such as lifestyle, associated with the condition have been taken into account (35, 36). For this reason, people suffering from type 2 diabetes may benefit from supplementing with glycine, although the scientific evidence is not yet sufficient to make specific recommendations. For people suffering from type 2 diabetes, the best way to reduce insulin resistance is to lose weight through diet and exercise (37).

Summary: Glycine supplementation could improve impaired insulin action. However, there are not yet sufficient data to make specific recommendations.

Glycine could protect against muscle loss

Glycine could reduce muscle wasting - a condition that can occur with age, malnutrition and when the body is exposed to severe stress such as cancer or severe burns. Muscle wasting leads to a detrimental reduction in muscle mass and strength, which can worsen the body's functional status and exacerbate other potentially existing diseases (38).

The amino acid leucine has been studied as a treatment for muscle wasting because it strongly inhibits muscle breakdown and promotes muscle gain (39). However, several changes that occur in the body during a state of muscle wasting impair the effectiveness of leucine in stimulating muscle growth. Interestingly, studies have shown that in mice suffering from muscle wasting diseases such as cancer, glycine was able to stimulate muscle growth while leucine was unable to do so (40, 41). Thus, glycine supplementation is promising in improving health by protecting against muscle loss in various forms of muscle wasting due to disease (42). However, further human studies are needed in this regard.

Summary: Glycine may protect existing muscle mass in diseases and conditions such as cancer, burns and malnutrition that are associated with muscle wasting.

It's easy to add extra glycine to your diet

Glycine is found in varying amounts in meat. You can also consume glycine in the form of gelatine. Gelatine is made from collagen and is added to many foods to improve their texture.

Other, more convenient ways to increase your glycine intake include the following:

Add glycine to foods and drinks

Glycine is available as a supplement in capsule or powder form. If you don't like swallowing capsules, you can also use glycine in powder form, which dissolves easily in water and has a sweet taste. In fact, the name glycine is derived from the Greek word for "sweet".

Due to its sweet taste, you can easily incorporate glycine powder into your diet by adding it to foods and drinks such as the following:

Coffee and tea
soups
oatmeal
protein shakes
yogurt
Pudding

Use collagen supplements

Glycine is the primary amino acid in collagen, the primary structural protein of connective tissue found in bones, skin, ligaments, tendons and joint cartilage. Accordingly, you can increase your glycine intake by using collagen supplements. This is probably even more efficient, as glycine competes with other amino acids for absorption in the digestive tract and is therefore absorbed less efficiently on its own than when bound to other amino acids, as is the case with collagen (43, 44).

Is glycine safe and harmless?

Glycine supplementation is safe and harmless in appropriate amounts. Studies have used up to 90 grams of glycine per day for several weeks without side effects (45). In comparison, the standard dosage used in studies is around 3 to 5 grams per day.

Conclusion

Glycine is an amino acid with impressive health benefits. The body needs glycine to produce important compounds such as glutathione, creatine and collagen. In addition, this amino acid can protect the liver from alcohol-induced damage and improve both sleep quality and health. Furthermore, glycine may also be beneficial for people suffering from type 2 diabetes and may also protect against muscle wasting that can occur in certain diseases associated with muscle wasting. Glycine intake can easily be increased by eating meat products, adding glycine powder to food and drink or supplementing with collagen.