We like to think we have a pretty good grasp on nutrition. Get enough macronutrients for your goals, and you should be set. Protein is protein, and we just need a lot of it. What if I told you even the balance of amino acids you’re getting is important, and can have a long-term impact on your health? There really are hidden factors in good nutrition, and one of the most important balances that few of us today are striking is that between methionine and glycine.
Methionine is one of the essential amino acids. Essential amino acids can’t be produced by the human body, and need to be supplemented through the diet. Methionine is particularly abundant in animal proteins like eggs, dairy products and most common cuts of meat. Methionine is one of the few amino acids that can contribute sulfur to biological processes. This allows methionine to methylate DNA, a foundational step of epigenetics(1). As Western diets are very high in animal proteins, they are also very high in methionine content, which is helpful for recovery, but without the right balance of another amino acid--glycine, we could cause problems in the long run.
The human body can produce glycine, but there are major enzymatic bottlenecks in that process that limit its effectiveness(2). Glycine is used throughout the body, so it should be supplemented to see benefits. Found in bones and connective tissue like collagen and gelatin, glycine is involved in detoxification, creatine synthesis, and collagen synthesis. Glycine has also been implicated in systemic anti-tumor, anti-inflammatory, and anti-diabetic effects(3, 4). Appropriate glycine levels (achieved through supplementation) allow for the production of glutathione, a major cellular antioxidant that helps defend against aging at a cellular level(5). Glycine is a powerful dietary supplement that most people in the U.S. are missing.
Methionine and glycine may seem like independent proteins, but they need one another at the individual and societal level. In the human body, methionine consumption has a direct negative relationship with glycine concentrations, meaning that each gram of methionine will increase glycine needs by 0.5 to 1 gram(6). Unfortunately, modern Western diets have deviated from an equitable consumption of both amino acids, in favor of a methionine-heavy regimen. Our overconsumption of skinless, boneless cuts of meat and underconsumption of connective and organ tissues means that our long term health is also at risk7. Methionine-restricted diets have been shown to increase lifespan in numerous organisms, as well as improving chronic inflammation and fat deposition8.
A methionine-heavy diet mimics the blood amino acid profile of a body under extreme physiological stress, and proper glycine supplementation can provide a systemic calming effect, promoting recovery. Most people don’t have easy access to headcheese or chicken feet soup, so they need to supplement their glycine from elsewhere. Collagen is an excellent source of glycine, with the amino acid being the most abundant in the molecular structure of collagen. Recommendations for proper glycine intake include about 1 gram of collagen protein per 10 grams of animal protein ingested. Because of the tax methionine exerts on glycine availability, you may need to increase that ratio as you increase the overall amount of protein in your diet(6). Generally, we recommend one scoop of collagen for every scoop of whey protein to keep the overall diet in balance.
The relationship between methionine and glycine may seem complex, but it’s a relatively new problem. Think about broths, curries, and other bone-based sauces used in traditional cooking - diets rich in these foods would have been balanced naturally. Over the past 100 years, our culture has increased the consumption of carbohydrates, fat, and methionine-rich protein, with a premium on convenience over nutritional value. Much of the fitness community is already comfortable with the idea of eating like our ancestors. If you’re interested in supplementing with more glycine in your diet, try cuts of meat with skin or bone, or try buying or making some bone broth. Not only will you be able to diversify your boring eating habits, but you’ll diversify your amino acid profile and give your body the chance to reap the benefits of glycine.
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