Is Glycine Keto-Friendly? Decoding the Amino Acid's Role in a Ketogenic Diet

October 26, 2025 •

5 min read

Did you know that despite being an amino acid and a building block of protein, glycine also has a naturally sweet taste? The question is glycine keto-friendly? is a common one among those pursuing a low-carb lifestyle, with the answer depending on understanding its unique metabolic properties.

Quick Summary

Glycine is a carb-free amino acid compatible with the keto diet, offering benefits like improved sleep, better fat digestion, and muscle support. However, it is glucogenic, meaning the body can convert it into glucose, which could affect ketosis in high doses.

Key Points

Keto-Compatible: Glycine is a carbohydrate-free amino acid, making it fully compatible with a ketogenic diet.
Glucogenic Potential: Despite being carb-free, glycine is a glucogenic amino acid, which means the body can convert it into glucose, potentially affecting ketosis at very high doses.
Supports Fat Digestion: Glycine is used in the synthesis of bile acids, which are crucial for the efficient digestion and absorption of fats in a high-fat keto diet.
Enhances Sleep and Recovery: Studies show that supplementing with glycine before bed can improve sleep quality, reduce daytime sleepiness, and aid in muscle recovery.
Aids Muscle Preservation: Research in animal models suggests that glycine supplementation can help preserve lean muscle mass while accelerating fat loss during calorie restriction, a common goal on keto.
Blood Sugar Impact: While associated with improved insulin sensitivity, consuming large doses of glycine may lead to a temporary blood sugar increase in some individuals due to gluconeogenesis.
Found in Keto Foods: Excellent natural sources of glycine suitable for a keto diet include bone broth, collagen powder, and cuts of meat with connective tissue.

What is Glycine?

Glycine is the simplest of all amino acids and is considered 'nonessential' because the human body can synthesize it from other amino acids. It plays several crucial roles, acting as a precursor for the body's primary antioxidant, glutathione, and the compound creatine, which fuels muscles. Glycine is also a major component of collagen, the most abundant structural protein in the body, providing strength to connective tissues, skin, and bones. Beyond its structural and metabolic functions, glycine also serves as an inhibitory neurotransmitter in the brain and spinal cord, promoting a calming effect.

Is Glycine Keto-Friendly? The Glucogenic Conundrum

On the surface, glycine appears perfectly suited for a ketogenic diet, as it contains zero carbohydrates. However, a key detail for anyone in ketosis is understanding its metabolic fate. While fats are metabolized into ketones for energy, and carbs are metabolized into glucose, amino acids like glycine have a more complex role.

The Role of Gluconeogenesis

Glycine is classified as a glucogenic amino acid. This means that if the body requires more glucose for energy—which can happen during fasting or a strict low-carb diet—it can convert glycine into glucose through a process called gluconeogenesis. For most individuals on a standard keto diet, consuming glycine from food sources or moderate supplementation is unlikely to cause a significant issue or knock them out of ketosis. The body uses this pathway as a backup, and the amount of glucose produced from a typical glycine dose is generally minimal compared to a carbohydrate-rich food. However, for those aiming for a very deep level of ketosis, such as for therapeutic purposes, the impact of high-dose glycine should be monitored.

Blood Sugar and Ketone Levels

Some evidence suggests that large doses of glycine may have a noticeable impact on blood sugar and ketone levels. A case mentioned in one source involved a keto dieter whose blood sugar spiked after consuming a product with a significant amount of glycine. It's also important to note that studies show glycine can affect insulin responses and blood glucose levels. Therefore, while a low-carb delight, the quantity is a vital factor to consider.

The Benefits of Glycine on a Ketogenic Diet

Far from just being a neutral amino acid, glycine offers several advantages for those following a ketogenic lifestyle:

Supports Fat Metabolism: Glycine is used by the body to produce bile acids, which are essential for the digestion and absorption of dietary fats. Given that the keto diet is high in fat, sufficient bile acid production is critical for smooth digestion and nutrient uptake.
Aids Muscle Preservation: During periods of calorie restriction, such as when following a ketogenic diet for weight loss, the body can break down muscle for energy. Studies suggest that glycine supplementation may help preserve lean muscle mass and accelerate fat loss, particularly during periods of calorie deficit.
Enhances Sleep Quality: Many people on keto report improved sleep, and glycine may contribute to this benefit. It has a calming effect on the brain, helping people fall asleep faster and improving overall sleep quality.
Reduces Inflammation and Oxidative Stress: As a precursor to glutathione, glycine boosts the body's antioxidant capacity. This helps combat oxidative stress and may lower chronic inflammation, providing benefits for overall health.

How to Incorporate Glycine into Your Keto Diet

Glycine can be obtained from both food sources and supplements, allowing for flexible incorporation into a ketogenic plan.

Natural Food Sources (Keto-Friendly)

For those who prefer to get their nutrients from whole foods, several glycine-rich options fit perfectly into a keto diet:

Bone Broth: One of the most popular sources, providing collagen and gelatin, which are high in glycine.
Gelatin and Collagen Powder: These powders are processed from animal collagen and are a concentrated source of glycine.
Meat and Poultry (Connective Tissue): Tougher cuts of meat, skin-on poultry, and organ meats contain higher amounts of connective tissue, and thus, more glycine.
Eggs: The protein in eggs contains a good spectrum of amino acids, including glycine.

Supplemental Glycine

For targeted benefits or to increase intake, glycine powder is an easy and effective option. Because of its sweet taste, it can be added to coffee, tea, smoothies, or even used as a zero-carb sweetener in baking. A typical dose used in studies for sleep improvement is around 3 grams before bed.

Glycine Dosage and Potential Side Effects

Glycine is generally considered safe, with studies testing high doses (up to 90 grams per day) without serious side effects, although the standard dose is significantly lower. Mild gastrointestinal distress can occur with high intake, and it's always wise to consult a healthcare professional before starting any new supplement. While the glucogenic effect of glycine is a metabolic reality, its impact on ketosis is largely dose-dependent. For those concerned about blood sugar spikes, especially on a very strict keto protocol, moderate intake from food or small supplemental doses is recommended, and blood glucose/ketone levels can be monitored for peace of mind. A ketogenic diet with glycine supplementation has shown to have positive effects on fat loss and muscle mass during caloric restriction.

Comparison: Glycine Sources


Feature	Collagen/Gelatin Powder	Bone Broth	Supplemental Glycine Powder
Glycine Concentration	High	Moderate (Varies)	Very High (Pure)
Convenience	High (Mixes into drinks)	Moderate (Requires preparation or purchasing pre-made)	Very High (Easy to measure)
Other Nutrients	Other amino acids, some minerals	High in minerals and other nutrients	Pure glycine; no other nutrients
Cost	Varies, can be more expensive	Can be inexpensive if homemade	Relatively affordable
Taste	Neutral or slightly sweet	Savory	Sweet
Best For	General supplementation, skin/joint health	Maximizing nutrient intake from whole foods	Targeted high-dose supplementation (e.g., for sleep)

Conclusion: Is Glycine Right for Your Keto Journey?

The short answer is yes, glycine is keto-friendly due to its lack of carbohydrates. However, a more complete answer acknowledges that as a glucogenic amino acid, large supplemental doses have the potential to impact blood glucose levels via gluconeogenesis. For the average keto dieter, moderate intake from sources like bone broth or small amounts of supplementation is a valuable addition to support collagen synthesis, aid fat digestion, and improve sleep quality. For those on a very strict therapeutic ketogenic regimen, careful monitoring of blood glucose and ketones is advisable when experimenting with higher doses. Ultimately, by understanding glycine's metabolic dual nature, you can use it to enhance your diet effectively and reap its many potential benefits.

This article is for informational purposes only and is not medical advice. Consult a healthcare professional before beginning any new supplement or dietary regimen.

Frequently Asked Questions

No, glycine is an amino acid, which means it contains no carbohydrates and is compatible with a ketogenic diet.

In high doses, glycine can be converted into glucose by the liver through a process called gluconeogenesis. For most people, moderate amounts won't affect ketosis, but those on a strict therapeutic keto diet should monitor their response, especially with large supplemental doses.

The primary benefits include supporting collagen production for joint and skin health, aiding fat digestion, enhancing sleep quality, and helping to preserve lean muscle mass during weight loss.

Glycine can influence blood sugar by stimulating insulin secretion and is also glucogenic. While often linked to better insulin sensitivity, high supplemental intake could cause a temporary blood sugar increase in some individuals.

Keto-friendly foods high in glycine include bone broth, collagen and gelatin powders, skin-on poultry, and tougher cuts of meat that contain connective tissue.

For purposes like improving sleep, studies have commonly used doses of around 3 grams before bedtime. While much higher doses have been tested, it is best to start with a conservative amount.

Yes, glycine has a naturally sweet flavor, making the powdered form a pleasant addition to drinks like coffee or tea on a keto diet.