Methionine and glycine are two amino acids found in the foods we eat that can have an enormous impact on our mental, emotional, and physical health.

Both of them are needed to protect our tissues from wear and tear as we age, to help us heal well when we get injured, and to prevent degenerative diseases like diabetes, heart disease, stroke, and cancer.

But they also have unique functions that make it important to balance them. Methionine helps prevent fatty liver disease, which affects an estimated 70 million Americans. It makes us mentally more flexible, and can help cool our anxiety or lift us from depression when our minds are rigidly ruminating on negative thoughts. Glycine helps stabilize our blood sugar. It helps stabilize our mind, to prevent us from drifting into endless distractions. It promotes healthy sleep, and it revitalizes our skin and bones.

The reason it is important to balance these amino acids is that consuming too much methionine can deplete our glycine levels. Methionine is especially abundant in eggs, dairy, meat, poultry, and fish. Glycine is especially abundant in skin and bones. While our ancestors tended to eat “nose-to-tail,” making liberal use of the skin and bones of the animals they ate, we tend to eat the meat and throw out the skin and bones. For example, skinless, boneless chicken breast is rich in methionine, but the glycine-rich skin and bones have been removed.

This article contains a searchable database of the methionine/glycine balance of almost 4000 foods. You can skip to the database with this link, or keep reading for more context.

How Much Methionine Do We Need?

It is better to focus on getting enough protein than on getting enough methionine, because if we get enough protein we will almost certainly get enough methionine.

If you are just trying to be healthy and not trying to achieve a goal related to body composition or athletics, 1.2 grams of protein per kilogram body weight or 0.5 grams of protein per pound of bodyweight should be enough. If you are trying to lose weight without losing lean mass, trying to gain muscle, or shooting for an athletic goal that depends on strength and muscle mass, you should double this amount, and sometimes consume more.

These amounts of protein will ensure you get enough methionine as long as you get them from animal sources or from a broad diversity of plant sources. When counting your animal protein, though, you should disregard protein from bones, bone broth, and gelatin or collagen supplements.

How Much Glycine Do We Need?

Estimates of how much dietary glycine we need range from 10 grams per day to 60 grams per day. Our needs are probably closer to 10 when we are in good health and closer to 60 when we are in poor health. In terms of what has been studied in humans, we can say the following:

3-5 grams of glycine before a meal helps stabilize blood sugar.
3 grams of glycine before bed helps improve sleep.
15 grams of gelatin before a workout helps improve collagen synthesis in our joints.
20 grams of glycine per day is used to treat some rare metabolic disorders.
60 grams of glycine per day has been used to treat schizophrenia.

If you were to add up the glycine from all of the specific uses you might use it for, it would all fall into the estimated 10-60 grams per day we need.

How Much Glycine Do We Need to Balance Methionine?

We do not have any rigorous human studies showing how much glycine we need to eat to make up for a given amount of methionine. We know, however, from biochemistry that methionine depletes glycine, and we know that our ancestors consumed much more glycine than we do.

The biochemistry predicts that every gram of methionine would increase our needs for glycine by 0.5-1 gram.

Plant-based diets that provide most of their protein as pulses and the remainder mainly as nuts and seeds tend to provide three to four times as much glycine as methionine. While crickets and many shellfish rival this ratio, most animal proteins provide only one or two times as much glycine as methionine. Collagen, found abundantly in the skin, bones, and other connective tissue of animals, provides 25 times as much glycine as methionine.

A simple way to bring a diet based on animal protein into the same glycine/methionine balance as a diet based on plant protein would be to add one gram of collagen for every 10 grams of non-collagen animal protein. For example, if you consume 100 grams of non-collagen animal protein, add 10 grams of collagen or a serving of bone broth that contains 10 grams of protein.

We might guess, though, that when you consume more protein than you need, the methionine is even more taxing. Let's say, for example, that you weigh 150 pounds and your minimal protein requirement is 75 grams per day. You are trying to build muscle, so you consume 150 grams of protein per day. If this is all non-collagen animal protein, you might add 7.5 grams of collagen for the first 75 grams of protein, and then 15 grams of collagen for the next 75 grams of protein, bringing your total collagen for a day to 22.5 grams.

If you applied the same reasoning to plant protein, you would ignore the protein contributing to your minimal requirement and then add one gram of collagen for every 10 grams of plant protein once you exceed that requirement.

A diet providing 150 grams of animal protein from steak and 22.5 grams of collagen would provide about 16.5 grams of glycine. This is within the estimated requirement of 10-60 grams per day. You would also have around 4 grams of excess methionine in your diet, which would demand an extra 2-4 grams of glycine over and above what you need without considering the methionine. Your glycine intake, at 16.5 grams, would provide 12.5 grams of glycine after fully compensating for the methionine, still within the range of 10-60 grams per day. You might consume more glycine, pushing your intake further up within this range, if you use it at the recommended doses for specific purposes like managing your blood sugar, promoting sleep, or boosting your joint health.

Where Should I Get My Glycine?

The database covers the glycine content of almost 4000 foods and supplements. If you are consuming foods with a glycine-to-methionine ratio between 3 and 4, the foods themselves are providing adequate glycine, at least until you start exceeding your minimal protein requirement.

To add extra glycine to your diet, the best foods are edible bones, such as those in canned fish; bone broth, as long as you can verify its protein content; hydrolyzed collagen or gelatin supplements, and pure glycine powder.

Bones, bone broth, gelatin, and collagen all have the advantage that they are better at promoting collagen synthesis than pure glycine. If your purpose is to benefit your joints, you should choose from among these.

Pure glycine powder has the advantage that it is sweet and can be used as a sugar substitute, and that it does not provide any other amino acids. Some people seem to get better sleep-promoting effects from pure glycine than from collagen, presumably because the glycine gets into the brain and fulfills its function better in the absence of the competing amino acids that would be found in collagen supplements or food protein.

If your purpose is stabilizing blood sugar, it probably doesn't matter.

Bone broth has culinary benefits: it can be enjoyed as a hot cup, like coffee or tea, and it can be used in cooking, to moisten low-fat dishes or to create a thicker texture or incorporate the taste of broth. It also contains traces of minerals and other bone components besides just collagen.

Edible bones have the advantage that they are very rich in calcium.

In addition to these sources, there is some glycine in certain mineral supplements. For example, 300 milligrams of calcium from calcium glycinate provides just over 1 gram of glycine, and 300 milligrams of magnesium from magnesium glycinate contains almost 2 grams of glycine. It is best to use these when you have a specific reason for supplementing with the mineral that is attached to the glycine.

Glycine Buying Recommendations

The collagen brands I trust most are Great Lakes and Vital Proteins. I personally use Great Lakes because it is less expensive, but I have a consulting client who finds that Vital Proteins is the only product that he digests well, possibly because they use enzymes instead of heat during processing.

Bulk Supplements sells a pure glycine powder that can be used as a sugar substitute or as a source of pure glycine whenever collagen is not a good choice. For example, I have a consulting client who finds that pure glycine, but not collagen, helps her sleep. For those who often have unexplained negative reactions to supplements that might be due to allergens or trace contaminants, I would use Pure Encapsulations glycine capsules.

For bone broth, the key is to verify the protein content. Kettle and Fire and Kitchen Basics both have 10 grams of protein per serving, which should supply about 3 grams of glycine. Kitchen Basics is less expensive, but Kettle and Fire boasts the best taste and quality.

If you join the CMJ Masterpass, you will have access to a storefront where you have a permanent 35% discount on Vital Proteins and Pure Encapsulations products. You will also get up to 30% off Kettle and Fire products. When signing up for the Masterpass, use the code GLYCINE to get a lifetime discount of 10% off the membership price.

Testing Recommendations for Glycine and Methionine Balance

This is the test you need!

Genova Methylation Panel

For help with interpretation, see here:

Interpreting the Genova Methylation Panel

How to Use The Database

This database has almost 4000 entries. Most of the entries come from the USDA nutrient database, which does provide raw data for glycine, methionine, protein, and Calories, but does not compute the ratios and percentages found in this database. In addition to data from the USDA, it incorporates data from the labels of many different supplements.

By default, the database is set to show the glycine-to-methionine ratio of all foods. You can limit the search to a single category, and you can search within all foods or within a category for specific keywords. I recommend selecting foods to obtain an average glycine-to-methionine ratio near or above 4.0 when averaged across the diet. If you fall substantially below 4.0, you can use glycine, gelatin, or collagen supplements to bring the ratio up.

You may, alternatively, want to find out how to get the most glycine or methionine per calorie, per 100-gram serving of food, or per gram of total protein. You can change the glycine-to-methionine ratio to the selection of the drop-down menu that best matches your objective. Once you turn up the search, you can click on “view more details” under any entry to get the complete set of glycine- and methionine-related values, as well as the source of the data and any special notes the entry might contain.

The Database

Adverse Effects of Glycine

There is some research suggesting that gelatin can raise oxalate levels. In theory, this could be harmful for someone at high risk of kidney stones. Glycine is less likely to do this than gelatin or collagen. If you know you are at a high risk of kidney stones, I recommend using glycine instead of gelatin or collagen and discussing this with your doctor. Outside of this one concern, very high doses of glycine have been studied without any adverse effects and it appears overwhelmingly safe.

Other Searchable Databases

Like this database? Here are three more!

Balancing Methionine and Glycine in Foods: The Database