Glycine Side Effects

Glycine is a non-essential amino acid touted for building proteins required for tissue maintenance and hormone synthesis.

Although glycine is considered safe and is well-tolerated by most people, side effects like nausea, stomach upset, vomiting, and fatigue may occur in some people taking glycine supplements. 

Quick Look:

• Glycine is a non-essential amino acid produced from serine, choline, and threonine.
• The amino acid glycine is involved in muscle function, digestion, sleep, immunity, and more.
• Nausea, vomiting, stomach upset, soft stools, and fatigue are among the side effects of taking glycine supplements.
• Your body requires about 2 grams per day of glycine, but the average dose for glycine supplements is 3 grams per day.

What is Glycine?

Glycine is a non-essential amino acid naturally produced in the body from three other compounds:

• Serine
• Choline
• Threonine

Its primary function is as a neurotransmitter (NT), but unlike many NTs, glycine has a dual function—as an excitatory and inhibitory neurotransmitter. It operates in the central nervous system (CNS) via N-methyl-D-aspartate type glutamate receptors and glycine receptors, respectively. 

What does that mean? Glycine can rev up the nervous system or cool it down depending on which receptor it binds to. If you need to sleep, glycine’s inhibitory actions can help reduce nervous system activity and induce relaxation and calmness, but if your nervous system needs to fire on high, its excitatory actions will do that.

What Does Glycine Do?

As an important amino acid, glycine doesn’t have a single role—it exerts widespread effects on various systems in the body. Some of the most important roles include:

• Memory and brain function
• Improving insulin sensitivity
• Supporting collagen production
• Promoting better digestion
• Enhancing immunity
• Boosting serotonin production

So, what’s in it for you?

1. Better muscle growth, strength, and performance
2. Healthier skin, bones, and joints
3. Better digestion
4. Stronger immune system
5. Regulated nervous system 
6. Better quality sleep

Key takeaway: Glycine’s dual role as both an excitatory and inhibitory neurotransmitter helps to support cognitive function, insulin sensitivity, immunity, sleep, and more. 

Benefits of Glycine Supplements

Boosts Glutathione Synthesis

Humans have a built-in antioxidant defense system to combat free radical production and reduce oxidative stress. Although several antioxidants are present in the body, glutathione is one of the most potent antioxidants. It’s synthesized from three precursors:

1. Glycine
2. Cysteine
3. Glutamic acid

Without sufficient glutathione, free radicals can build up and cause damage to healthy cells, leading to oxidative stress—and oxidative stress is an underlying factor in many chronic diseases, including neurological diseases, cardiovascular disease, diabetes, cancer, and more. 

Because glycine is required for glutathione synthesis, maintaining sufficient levels is vital for mitigating inflammation and oxidative stress and warding off diseases caused by excessive free radical damage. 

Enhances Creation Production

If you’re big into fitness, you’ve probably heard about creatine. It’s one of the most popular fitness supplements on the market, offering serious benefits for muscle growth. On its own, creatine is an amino acid concentrated in muscles and the brain. In technical terms, creatine and creatine phosphate act as buffers for ATP in tissues, maintaining proper ATP levels when the energy demand exceeds the ATP synthesis rate. In simple terms, creatine supplies energy for short-duration activities.

But what does glycine have to do with creatine? 

Glycine is one of three amino acids your body uses to produce creatine, along with arginine and methionine. As such, glycine supplementation may increase our body’s natural production of creatine to enhance energy, strength, and athletic performance. 

Supports Collagen Synthesis

Collagen is a big buzzword and is all the rage in the health and wellness world. It’s one of the most abundant proteins in the human body and plays a major role in the structure of connective tissues, such as the skin, bones, tendons, and joints. 

Studies have shown that collagen supplements are effective in improving osteoarthritis symptoms and fighting the signs of aging by improving skin moisture, elasticity, and hydration.

Because glycine is essential for collagen production, sufficient intake, either via dietary glycine or supplementation, is critical. 

Improves Sleep Quality

Glycine and sleep go hand in hand. Although glycine may not have a direct effect on sleep like melatonin or Montmorency tart cherries, glycine is involved in a few aspects of sleep:

• Serotonin (melatonin) production
• Reduces core body temperature
• Improves sleep latency
• Reduces insomnia symptoms 

Scientific evidence has shown that people who take glycine before bed fall asleep faster, enter a deeper sleep faster, and wake with less daytime fatigue the following day. Glycine and GABA can also be combined to improve sleep efficiency.

Key takeaway: Glycine’s involvement in several body systems benefits collagen production, creatine synthesis, antioxidant defenses, and sleep. 

The Most Common Glycine Side Effects

Before taking a glycine supplement, you’ll want to know about potential side effects. Although not common, they do happen, so knowing what to look for is important.

Glycine is generally considered safe as a supplement and is well-tolerated by healthy adults, but the following side effects may occur in some people:

• Nausea
• Vomiting
• Stomach upset
• Soft stools
• Fatigue

While supplementary glycine are safe for most people, there are two contraindications with this amino acid:

1. Pregnant or breastfeeding women: A lack of evidence on whether glycine supplements are safe during pregnancy or lactation means that pregnant or breastfeeding women should avoid supplement use. However, reaching your daily glycine requirements through diet is still crucial during pregnancy or lactation.
2. Schizophrenia drugs: People taking the drug Clozapine (brand name Clozaril) for schizophrenia should refrain from taking glycine supplements, as the combination could reduce the effectiveness of the medication. 

If you’re unsure whether supplementing with glycine is safe, consult your healthcare provider.

How to Take Glycine

There are two ways to increase levels of glycine:

1. Food sources
2. Glycine supplements

Food sources are one of the safest ways to increase glycine levels, as they’re more readily absorbed and harder to overdose. However, glycine is found in the highest concentrations in animal products, so vegetarians and vegans may find consuming enough dietary glycine challenging.

The other option is glycine supplementation. Glycine is widely available online and through health food stores as pure glycine or mixed with other amino acids or compounds. 

However, it’s important to remember that taking a single amino acid to support an underlying issue may offer beneficial effects, but ingesting too much of any single amino acid may disrupt the balance of amino acids in the body. That said, scientific evidence shows that glycine absorption is lower on its own than when bound to other amino acids.

Food Sources of Glycine

As mentioned, high-protein foods, especially animal products, are one of the best sources of dietary glycine. It’s found in the highest concentrations in the following foods:

• Bone broth (gelatin)
• Red meat
• Seeds
• Turkey
• Chicken
• Pork
• Peanuts
• Canned salmon 

In addition to the foods listed above, smaller amounts of dietary glycine can also be found in: 

• Beans/legumes
• Spinach
• Kale
• Cauliflower
• Cabbage
• Pumpkin
• Banana
• Kiwi

What’s the Right Glycine Dose to Avoid Side Effects?

As with any supplement, it’s hard to pinpoint the exact dose that will work for every individual. So, how much glycine do you need?

For a glycine supplement, most studies suggest that a dosage of 3 grams daily can elicit positive effects on things like sleep, joint health, and digestion. For more serious disorders like schizophrenia, high doses of up to 30 grams per day have been proven safe. 

Food sources should supply about 2 grams of glycine daily for optimal body functions.

Conclusion

Glycine benefits several health conditions, from digestive and sleep issues to joint pain and memory. It’s important to remember that when taking dietary supplements, side effects can happen. Although glycine side effects may not present as serious, knowing what to look for can reduce the risk of complications.

FAQs

Is glycine an amino acid?

Yes, glycine is a non-essential amino acid produced from three precursor amino acids: serine, choline, and threonine.

Can you take glycine during the day?

Glycine supplementation is safe at any point during the day. The beneficial effects of supplemental glycine have more to do with glycine levels in the body than when you take the supplement. However, if you’re after the sleep benefits of glycine, taking your supplement before bed might offer greater benefits. 

What is glycine made of?

The kidneys and liver synthesize glycine from choline, serine, hydroxyproline, and threonine.

Are there glycine benefits for skin?

Yes! Glycine is a significant component of collagen’s structure, the most abundant protein in the skin and other connective tissues. Using glycine supplements or applying glycine topically may help strengthen the skin matrix and increase its firmness. Glycine accelerates recovery of the skin and can enhance skin regeneration to reduce signs of aging.

What are the most common glycine supplement side effects?

Fatigue, nausea, vomiting, soft stools, and stomach upset are some of the most common side effects of glycine supplements.

Can I take glycine every day?

Oral glycine supplements are likely safe when taken in doses of up to 6 grams per day for four weeks. Although well-tolerated by most people, some may experience mild side effects, especially with higher doses.

What medications should not be taken with glycine?

People taking the drug Clozapine, used to treat schizophrenia, should avoid using glycine supplements, as they can interfere with the effectiveness of the medication.