In this video Dr. Ashley Frazee explains why the simple amino acid glycine, found even on comets, is crucial for human health. She describes glycine’s unique role as the smallest amino acid that fits into every third position of collagen’s triple‑helix, making it the “biological glue” of skin, cartilage, tendons, and bone. Although classified as non‑essential because the body can synthesize it, endogenous production averages only about 3 g per day, while physiological needs for collagen repair, creatine synthesis, and glutathione production are estimated at 10–15 g daily, creating a large dietary deficit. When glycine is insufficient, the body prioritizes short‑term survival functions (e.g., glutathione production) and deprioritizes long‑term tissue repair, leading to slower healing of joints, gut lining, and skin. Modern diets that emphasize lean muscle meat are high in methionine, which further depletes glycine because excess methionine must be processed using glycine. Dr. Frazee recommends two main strategies to close the gap: (1) ancestral eating patterns that include bone broth, cartilage, skin, and tough cuts of meat rich in connective tissue; and (2) supplementation with collagen peptides (≈33 % glycine) or pure free‑form glycine powder. She notes that 3–5 g of glycine taken before bedtime can improve sleep by promoting peripheral vasodilation and lowering core body temperature. The video also includes a sponsorship disclosure for Hume Health’s BodyPod body‑composition tracker, which she uses to monitor muscle mass, visceral fat, and other health metrics. The overall message is that despite being labeled non‑essential, glycine is a limiting nutrient that most people need to obtain from diet or supplements to support structural health and sleep.
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There is an amino acid inside your body that is so fundamental to life and the universe that scientists found it on a comet in space. In fact, astrobiologists have discovered that this amino acid can form on icy dust grains in space through dark chemistry. This exact same molecule is used by our bodies to build our skin, cartilage, tendons, and bones. So why is something so fundamental to life Also hanging out in space because this amino acid, glycine, is the simplest amino acid that exists. It's fundamental to life and structure itself. So what exactly is glycine? Well, like I said, it's an amino acid, and amino acids are the building blocks of proteins. Glycine just so happens to be the simplest and smallest of them all. And to your body, it's essentially biological glue because it virtually has no bulk. It's extremely It's extremely flexible, and it's the only molecule small enough to fit into the tight center of collagen's triple helix structure. Every 3rd amino acid in collagen has to be glycine. Take glycine away and the structure of collagen would fall apart. So why am I telling you all of this? Because I've come across a very interesting biological math problem. Interestingly, we call glycine a nonessential amino acid, meaning you don't need to eat it because your body can manufacture it internally from other molecules. But calling glycine nonessential hides an important math problem. Just because we can manufacture glycine ourselves, that doesn't mean we can make enough glycine. See, here's the math. Your body can make around 3 grams of glycine per day. However, a human adult needs roughly 10 to 15 grams of glycine every single day just to maintain basic physiological functions like repairing collagen for your joints, your skin, and your gut lining. Synthesizing creatine for energy and producing glutathione, your master antioxidant. In fact, it's one of the 3 amino acids that glutathione is made out of. And believe it or not, collagen makes up about 30% of your total body protein. And like I said, roughly 1 in every 3 amino acids in collagen is glycine. And maintaining collagen, or the stuff in bone and connective tissue, consumes the vast majority of glycine in your body. So if you make 3 grams, but you need 15 grams, what are you supposed to do? See, this leaves a massive 10-gram daily deficit that has to come from diet. But this next thing I'm going to tell you actually dropped my jaw when I learned it, because nobody taught me this in medical school. See, here are the consequences of the deficit. When your body doesn't get enough glycine, It performs biological triage. I've learned that a lot with most things, but your body will prioritize immediate survival, and it will use the available glycine to make glutathione to fight oxidative stress or manage toxicity or things going through your liver. So what gets deprioritized is long-term structural integrity. So your body quite literally stops repairing the collagen in your knees, lining of your gut and the elastin in your skin because it's using its limited glycine budget just to keep the lights on. I mean, is this why I can't heal my wrist with peptides? Now I'm going to give you some simple tips on how to get more glycine, but first let me go further on why we lose it in the first place. See, for thousands of years, humans ate meats nose to tail. We consumed the muscle of the animals like we do now, but we also ate the skin We chewed the cartilage, and we boiled the bones into broth. Kind of grosses me out, but those connective tissues are densely packed with glycine. And modern food processing and our dietary habits today have kind of engineered all of that away. And now we prioritize boneless, skinless chicken breasts and lean steaks, right? These muscle meats are fantastic for protein, but they're incredibly high in a different amino acid called methionine. And here's the kicker: your body actually consumes, or uses up, glycine in order to process and clear excess methionine. So by eating a modern muscle meat-heavy diet, we're not just missing out on dietary glycine, we're actively draining our already limited homemade supply. It's like a biological double whammy. So if you're not into eating tendons and bones, well, what can you do to bridge the gap that you have? Because you absolutely have to bridge the gap. And I treat a lot of highly active weightlifters, and sometimes they ask me, why am I all of a sudden getting hurt and not recovering well? And I wonder if this is one puzzle piece that we could utilize. So here are some practical solutions on how to bridge your glycine gap. The way I see it, there are 2 different easy pathways depending on how you prefer to manage your own biology. Number one is the ancestral dietary fix. So to get glycine from food, you have to eat the structural components of the animal, the parts we usually throw in the trash. But I'm not eating joints and tendons. I tried chicken feet as a kid, but it just wasn't for me. So if you're like me, consider trying bone broth or the tougher cuts of meat. So real slow-simmered bone broth is made by simmering bones in broth, and this pulls the glycine out of the bones and connective tissue and yields high amounts of glycine in the broth itself. So it's not just good for protein, it's good for glycine-heavy protein. And the tough cuts of meat are things like chuck roasts, ribs, shanks. These contain high amounts of connective tissue, and when cooked low and slow, that tough connective tissue literally melts into gelatin, which is essentially pure collagen and therefore loaded with glycine. You can also eat the skin on animals like poultry and fish and Not shy away from the gristle. I'm going to attempt to take my own advice here because that sounds like the most natural route, but I also envision myself buying some supplements if I can't stomach it. So if you'd like to do that, here are the supplement alternatives to eating tendons. Collagen peptides. Simple, right? Well, a high-quality collagen powder is about 33% glycine by weight. So if you're like me and you're somebody who drinks coffee, you can add collagen to that. It's very easy. I add about 10 to 15 grams of collagen every morning to my coffee. And I've been trying this one out from MDhair because I asked my hairdresser how to improve my hair, and I actually got to say I really like it. So I'll link that and another brand that I use in the description. There's also pure freeform glycine. This is the most direct route. It comes as a white powder, and because of its molecular structure, it's incredibly sweet. Apparently very much like real sugar. And I'm going to come back to this in just a second because I want you to remember there is a distinction between eating muscle and maintaining your own muscle, which is why I'm going to promote one of my favorite products here. I'm a clinician at heart, and whether I'm working with somebody to lose weight or improve their longevity, I can't help but to encourage as much muscle building or muscle preservation as possible, as I believe high muscle mass is one of the major keys to longevity. And so I'm working to get more patients into a habit of tracking not just their weight, but their body composition. And whether that's with a DEXA scan or the fancy scale at your gym, or you can use a home tracker like I do. And I use the Hume BodyPod. And really honestly, I am obsessed with mine because when I started trying out different home trackers, the Hume Pod was spot on with my actual DEXA scan done about 2 days prior. It also measures things like a visceral fat index. Muscle mass, hydration, and other metabolic markers that you can track over time. With the Hume Body Pod, you can easily understand how your body reacts to things like different foods, sleep, stress, and other factors so that you can start making informed choices. And Hume has been kind enough to sponsor several of my videos so that I can continue making content for you, and they're sponsoring this video too. So thank you to Hume Health for allowing me to do this. If you click on the link in my description, my discount code can combine with any of Hume's current discounts to get you up to 50% off the total, and you can use an FSA or an HSA for it. Please have some way to track your body composition. It will tell you more about your health than your weight does. Now there's an unexpected benefit to supplementing with glycine that I need to tell you about, and that's sleep improvement. Like I said, pure glycine powder has a sweet taste. In fact, a lot of people use 3 to 5 grams of glycine powder as like a sugar replacement in tea or water right before bed. And this bridges their glycine gap deficit, helps them with sweet cravings, and can trigger a useful drop in your core temperature before bed, which can help with getting into deep sleep. Clinical studies consistently show that if you take 3 grams of glycine within 60 minutes before bed, well, glycine hits its peak concentration in the brain just as you're naturally starting to wind down. It hits receptors in the brain that signal nighttime. I promise I did not make that up. Glycine also triggers peripheral vasodilation, causing a shift of blood flow from your core to your hands and your feet, and this drops your core temperature. And this is like a biological green light for your brain to initiate the cascade of events that trigger deep sleep. I hope you're fascinated by that, 'cause I really was. Well, let's zoom back out to that comet that we found glycine on in space. Glycine is an incredibly simple molecule. We find it in the chemistry of space, and we find that same molecule playing an essential structural role inside our bodies, right down to the center of the collagen holding our skin and bones and tendons together. And I personally find that incredible and important for us to know. Something so small and simple is woven throughout creation, and inside of us it's doing an enormous job. We call it nonessential, but don't let that fool you. And after learning all of this, I'm definitely going to make sure that I'm getting more glycine. I'm Dr. Ashley Frazee. I'm a primary care physician, and I have a degree in nutrition and a passion for understanding what really matters. If you like this video, please hit like for me and subscribe to my channel, and I hope you have the best day.
