You can get glycine from three sources: your body makes about 3 grams per day on its own, food provides another 1.5 to 3 grams daily, and supplements can fill any remaining gap. For most people, the combination of diet and internal production covers basic needs, but research suggests the body’s manufacturing capacity falls short of what’s needed for optimal collagen turnover and other metabolic demands. Here’s how each source works and how to make the most of them.
How Much Glycine You Actually Need
The recommended dietary intake of glycine is 1.5 to 3 grams per day, but that number may understate the real demand. Your body uses glycine for building collagen (the most abundant protein in your body), producing the antioxidant glutathione, supporting brain function, and synthesizing other compounds like creatine and heme. Collagen alone is roughly one-third glycine by weight, so any tissue repair, joint maintenance, or skin turnover draws heavily on your glycine supply.
Your body synthesizes about 3 grams of glycine daily, primarily by converting the amino acid serine. Combined with a typical diet, that gives most adults somewhere around 4.5 to 6 grams per day total. But researchers have described glycine biosynthesis as “a weak link in metabolism,” noting that the body’s production capacity doesn’t fully satisfy collagen synthesis needs. The shortfall is more pronounced in older adults, people under high physical stress, and athletes in demanding training cycles.
Best Food Sources of Glycine
Glycine is found in virtually all protein-containing foods, but the richest sources by far are collagen-heavy animal foods: bone broth, skin-on poultry, pork rinds, and gelatin. A cup of bone broth can deliver 2 to 3 grams of glycine depending on how long the bones were simmered. Gelatin, which is essentially cooked collagen, is roughly 25 to 30% glycine by weight, making even a tablespoon a meaningful source.
Meat, fish, and dairy all provide glycine, though at lower concentrations than connective-tissue-rich foods. A typical serving of chicken breast, beef, or salmon provides about 1 to 2 grams. Eggs contribute smaller but consistent amounts, especially the whites.
Plant-Based Sources
If you eat a vegetarian or vegan diet, you can still get glycine, though the concentrations are lower per serving. Among plant protein isolates, brown rice protein is the richest source at 3.4 grams of glycine per 100 grams, followed by potato protein (3.2 g), pea protein (2.8 g), soy protein (2.7 g), and microalgae (2.6 g). Wheat, lupin, and hemp protein isolates fall in the 2.1 to 2.4 gram range. Keep in mind these values are for concentrated protein isolates, not whole foods. You’d need to eat substantially more whole rice or peas to reach those numbers. Combining legumes with grains throughout the day is a practical way to build up your glycine intake on a plant-based diet, though supplementation is worth considering if you’re aiming for higher amounts.
Glycine Supplements
Glycine is sold as a pure powder or in capsules, and it’s one of the more affordable amino acid supplements. The powder dissolves easily in water and has a mildly sweet taste, which makes it simple to add to drinks or food. Most supplement doses range from 3 to 5 grams per day.
The best-studied dose for sleep benefits is 3 grams taken before bedtime. In clinical trials, this amount improved subjective sleep quality, reduced daytime sleepiness and fatigue, and shortened the time it took to reach deep slow-wave sleep, all without altering overall sleep architecture. Participants in these studies had either insomnia tendencies or restricted sleep schedules, so the effects are most relevant if you struggle with sleep quality rather than simply wanting to sleep longer.
For collagen support or general wellness, doses of 5 to 15 grams per day appear in the research literature, sometimes split between meals. No formal upper limit has been established, and side effects at typical supplemental doses are rare. Some people report mild gastrointestinal discomfort at higher doses, which usually resolves by splitting the amount across the day.
How Your Body Makes Glycine
About 35% of your body’s glycine comes from internal production, and the vast majority of that, around 87%, is made by converting serine into glycine. This conversion happens in both the main body of your cells and inside mitochondria, using an enzyme called serine hydroxymethyltransferase. The reaction also produces a molecule your cells need for DNA synthesis, which is why this pathway is tightly regulated.
Smaller amounts of glycine come from the breakdown of choline (found in eggs, liver, and soybeans) through a chain of intermediate compounds. Your liver can also produce glycine through a reversible reaction, though this same enzyme system is equally capable of breaking glycine down, so it doesn’t always work in your favor.
The rate-limiting step in glycine production appears to be the serine conversion itself. This is why researchers have concluded that your body simply can’t manufacture enough glycine to cover all its metabolic uses, particularly the enormous demand created by collagen maintenance. Eating adequate protein, especially serine-rich foods like eggs, soy, and dairy, supports your body’s internal glycine production, but diet alone is the more reliable lever for increasing your total supply.
Why Glycine Matters for Collagen
Collagen is the structural protein in your skin, joints, tendons, bones, and blood vessels. Every third amino acid in collagen’s repeating chain is glycine, making it the single largest ingredient in collagen production. When glycine availability drops, your cells can compensate to a point by ramping up internal synthesis from glucose and serine, but this workaround has limits.
Research on fibroblasts, the cells responsible for producing collagen during wound healing and tissue maintenance, shows that when external glycine and serine are removed, cells increasingly divert glucose to manufacture their own glycine. But when glucose is also limited, or when the signaling pathway driving this compensation is blocked, collagen production drops significantly. Adding glycine back to the environment partially rescues collagen output even under those stressed conditions. This suggests that keeping glycine levels topped up through diet or supplements gives your cells a reliable building block without forcing them into metabolic workarounds.
Practical Tips for Increasing Glycine Intake
- Cook with bone broth. Use it as a base for soups, stews, or rice instead of water. A cup or two daily adds 2 to 5 grams of glycine along with other collagen-derived amino acids.
- Add gelatin to foods. Stir unflavored gelatin into smoothies, oatmeal, or homemade gummies. A tablespoon provides roughly 1.5 to 2 grams of glycine.
- Choose collagen-rich cuts. Skin-on chicken thighs, slow-cooked chuck roast, and oxtail deliver more glycine than lean cuts like chicken breast or sirloin.
- Use glycine powder at bedtime. Dissolve 3 grams in warm water or herbal tea before sleep if you’re targeting both collagen and sleep quality.
- Stack plant proteins. If you’re plant-based, combining pea protein or brown rice protein into shakes gives you the highest glycine yield per serving among non-animal options.
One Caution Worth Knowing
Most of the research on glycine supplementation is positive, but one animal study raised an important flag. In mice fed a high-fat, high-sugar diet to model obesity, adding glycine to their drinking water for six weeks actually worsened fasting blood sugar and increased liver gluconeogenesis, the process where the liver produces new glucose. The glycine didn’t improve muscle insulin sensitivity either. This doesn’t mean glycine is harmful for everyone, but it suggests that if you’re dealing with significant insulin resistance or metabolic syndrome, the interaction between glycine and liver metabolism may not be straightforward. The study used a modest dose in an obesity model, so the relevance to lean, healthy people is likely minimal.