Updated: May 17, 2019
Bone broth or animal stock has recently attracted attention for its health effects. There's a general understanding that it's excellent for digestion and that you should eat it if you're ill. But, um, what's the reason for that again? Something about collagen, or is it gelatin, and glycine? So long as you reference one and claim that it's great for your belly, that seems to be enough to praise it and add it to your staple foods. That's all true. It's a great thing that more people are embracing the benefits of bone broth and other traditionally prepared foods. But it's important that people also understand the reasoning behind it because that's the information that verifies the health messages around us. That's the missing link that helps us to make informed choices about our food sources and see the bigger picture. If our practice is just to stop at the final conclusion that 'eating A food is healthy because it does B', then that limits our ability to critically assess health information and apply it to our lives to make it practical and useful.
This infographic contains the bare basics. For more details, you'll find a simplified description of the proteins and amino acids that play a role at the end of this article.
Translating this into foods
Here are some simple strategies you can apply to help you balance your glycine intake, no number crunching required.
Eat all the different parts of the animal. This has recently become popular under the label of 'nose to tail' eating - essentially, the concept is that you use of all of the cuts of the animal rather than only eat the meat. Beyond just glycine, this helps to ensure that you eat the array of amino acids that your body needs. Different cuts of an animal have different amino acid profiles. You'll find collagen concentrated in skin, bones, connective tissue (the tissue of the tendons that connects muscles to bones), tendons and ligaments.
For example, cuts that contain a high amount of connective tissue include chuck, blade and shin - you'll be able to see the seams of connective tissue in cuts like chuck steak or osso bucco. Look for cuts that contain a bone - if there's bone, there's connective tissue around it, like in blade steak or around the ribs.
Embrace (don't avoid) eating some of the best natural sources of collagen, like organ meats. In contrast, cuts like rump, tenderloin, round and topside have little connective tissue. Cuts that are high in collagen should be cooked using a slow, moist heat, such as stewing or braising. The more collagen, the tougher the cut. You can also slice collagen-dense meat into smaller pieces or mince it to make the fibres smaller and easier to break.
Make bone broth. Bone broth or stock adds taste to a meal, adds moisture and is a soothing hot drink and a change from tea or coffee. The collagen fibres in the connective tissue soften and melt while cooking and add a rich flavour to the meat. You'll need to cook in for a long time at a simmer to maximise the amount of collagen that's released from the bones (ideally 24 - 48 hours). 'Broth' typically refers to a longer cooking time than 'stock', increasing its nutrient content, but whether it's a broth or a stock prepared in less time (say 4 - 8 hours), it's still a nourishing food that soothes the digestive system and has broader health benefits for your body.
Make it at home! Even though it's time consuming, making your broth is far better than buying it. The so called broth and stock that you find in your grocery store often aren't the real thing. If you check the ingredients, you'll see that the companies tend to use meat flavours and often add MSG. Even if the ingredient list is legitimate, you can't tell whether the product is made from quality, grass fed bones (probably not) or if it's been simmered for long enough to maximise the benefits. If you do it at home, you can make sure that you're consuming the nutrients you're after. Choose quality beef if you are cooking with bones, because chemicals that enter the animal’s body are stored in fat and bone tissue and can then be released with cooking. Eat edible bones. It can seem a little creepy because the texture is unusual, but don't discard the edible bones in foods like canned sardines or other fish. They are an excellent source of collagen and also rich in calcium. Supplements are another option, and you can supplement a quality glycine. But start adding more food sources first.
Making sense of the details
Let's keep this simple. The aim here is to develop your understanding of bone broth and its effects on digestion so that you actually grasp the method behind the claims. There's far more information available out there on this topic and all its elements, but after reading this article you should be able to grasp the basics and quickly explain it to others.
Glycine, collagen and gelatin ... what's the difference?
First, let's clarify the basic building blocks that we're talking about here.
Collagen is a protein in our bodies that is predominantly found in skin, bones, tendons and the digestive system. It's the most abundant protein in humans and many mammals. Collagen plays a key role in our skin, making it strong and elastic, and our joints and tendons, keeping us strong and supple. It's like a super glue that helps to hold the body together. Our bodies make less collagen as we age (cue wrinkles, sagging skin and joint pains). It is also a primary component of the connective tissue that lines that digestive tract and helps to 'heal and seal' the gut wall. Collagen is made up of many different amino acids forming a strong chain that takes a while to disintegrate. This is the reason that you need to cook animal cuts for a long time until the collagen starts to soften and becomes tender and palatable - if it's not cooked properly, it's tough to eat. Gelatin is a related protein to collagen. People often refer to collagen and gelatin interchangeably. That’s because gelatin is made from collagen — after collagen breaks down, it transforms into gelatin. You can literally see this at work if you make bone broth or slow cook cuts of meat - the collagen changes, softens and becomes a liquid (ie, while you're eating it) and semi solidifies after it cools (ie, if you cool a broth or a dish that contains gelatin and it turns to a jelly like substance).
Recap: Gelatin and collagen both contain the same stuff that have the same benefits in the body, it's just delivered in a different form.
Glycine is one of the main amino acids that makes up collagen protein chains. About a third of the protein found in collagen is glycine. Glycine is a non-essential (or sometimes called a conditional) amino acid, and even though your body can produce it in small amounts, it may need a little help from outside sources, particularly in a trained, stressed or inflamed person. Glycine is found in concentrated amounts in collagen and also gelatin. Glycine is found in many human enzymes and proteins and plays a role at multiple sites across the body. It is abundant in the skin and bones of humans and other animals. Some of its vital roles in our health include:
To synthesise collagen in our joints and repair and protect our tissues
To promote healing from injury or illness
To facilitate Phase II detoxification pathways
To help control blood sugar
To promote sleep
To make creatine and promote healthy muscle building and boost energy production while training
How does collagen (and gelatin, and glycine) support digestion?
A key benefit that features in the mainstream is the effect of collagen (and gelatin, and glycine) on digestion. Collagen helps to soothe and rebuild the protective mucosal lining of the GI tract and maintain the integrity of the intestinal wall. The amino acids in collagen (like glycine) build the tissue that lines the GI tract and the colon. A strong gut lining is a good thing because it makes it easier for your body to:
Absorb the nutrients from your foods
Manage difficult-to-digest foods
Handle food intolerances and sensitivities
Soothe symptoms of digestive distress
Reduce gut permeability (ie, particles leaching out of the gut and into circulation uninvited that contribute to systemic inflammation and sound the alarm for an immune response).
How much glycine do I need?
The amount of glycine that your body needs depends on a number of things. If you train frequently, put your joints under load often, you're stressed, have digestive troubles, struggle to sleep or are recovering from an injury or illness, your body could probably use extra glycine. One thing that's clear is that the standard Western diet prefers animal cuts that aren't high in glycine. If, like most people, you mainly eat animal proteins from muscle meats, this may meet your protein and methionine needs but fall short of your glycine requirements. [A] Remember, that's because glycine is concentrated in collagen, found in the skin, bones and connective tissues of animals. It's estimated that you need in the range of 10 g to 60 g of glycine each day. In contrast, most people only consume only about 2 g of glycine from their diets daily. Eating foods rich in gelatin and glycine promote collagen synthesis. It's not as simple as eat collagen, make collagen. The foods you eat must be digested, and our bodies break the proteins (like collagen and gelatin) into amino acids (like glycine). Our bodies also use other vitamins and minerals to actually make collagen from the necessary amino acids available to it (for example, vitamin C) and fats to properly absorb it.
The Western A Price Foundation, Why Broth is Beautiful: Essential Roles for Proline, Glycine and Gelatin
Dr Chris Masterjohn, Balancing Methionine and Glycine in Foods: The Database
[A] A note on methionine
Did you know that consuming too much methionine (another amino acid) can deplete your glycine levels? Methionine rich foods include eggs, dairy, meat, poultry and fish. If you'd like to explore the numbers, there's other leading thinkers like Dr Chris Masterjohn that have considered the glycine to methionine ratio in precise foods. If you'd like to delve into the food by food details, Dr Masterjohn has compiled a thorough searchable database of the methionine to glycine balance of almost 4000 foods. You could also track the nutrient information in an app like Cronometer, as it is supplied via its preferred databases. But you don't need to do that. It's actually tricky to identify the exact amount of glycine that you consume if you make your bone broth from scratch, because there's no protein panel on the label that you can use to verify its protein content (10 g of protein from broth supplies about 3 g of glycine). The main message here is to understand that the ratio of glycine to methionine dramatically varies based on the cut of meat - for example, Dr Chris Masterjohn indicates that most animal proteins provide only 1 or 2 x as much glycine as methionine, but collagen contains about 25 x more glycine than methionine.