Written by Chris Kresser
Traditional cooking uses meat bones as a base for delicious stock because it is the secret to cooking great recipes. But it’s also incredibly nutritious and has scores of health benefits. Read on to learn more about bone broth and why you should make it a staple in your diet.
The Weston A. Price Foundation and advocates of the Paleo and Primal lifestyles favor bone broth for its wide array of nutrients that are difficult to find in any other food source. Dr. Natasha Campbell-McBride has made bone and meat stock the foundation of the GAPS protocol because of its ability to heal and seal the gut lining and reduce overgrowth of harmful microbes. Chicken broth has also been suggested to reduce the migration of immune cells during illness. These are just some of the many reasons to love bone broth.
Bone broth is mentioned in dozens of articles on my blog, but I haven’t really provided a thorough analysis in a single, convenient place for my readers. So here it is: everything you need to know about bone broth! In this research-dense article, I will cover the role of broth in traditional cultures, the nutritive components of bone broth, the numerous health benefits, and the best ways to source it.
Bone broth in traditional cultures
A South American proverb says “good broth will resurrect the dead.” While this is certainly a stretch of the imagination, the ability of broth, and chicken broth in particular, to treat the common cold has long been touted as ancient folk wisdom. Scientists at the University of Nebraska sought to test this folklore in 2000 and found that in vitro (in a Petri dish), some components of chicken soup were able to inhibit the migration of innate immune cells called neutrophils, effectively acting as an anti-inflammatory that could, in theory, reduce symptoms of illness (1). Whether this effect occurs in vivo (in a living organism) is still unclear, but this preliminary data suggests that our ancestors may have been onto something. We’ll explore the bone broth–immune system connection more in a later section.
Evidence of the existence of soup can be found as far back as about 20,000 BC (2), and it’s well accepted that broth of some sort was, and remains, a staple in many traditional cultures. In Danish and German culture, large hens were specifically reserved for making soup, and the cooked meat was retained for other dishes or added back to the soup. In East Asian diets, dishes like miso sometimes contain meat stock. In Greece, beaten eggs mixed with lemon are commonly added to chicken broth as a traditional remedy for colds and digestive upset. Chicken soup in Hungary usually included organs like chicken liver and heart, while in Vietnam and the Philippines, beef bone marrow was used as the base for making soup. In India, chicken soup is popularly sold by roadside vendors in the winter and takes on many different forms. Chicken soup was a traditional dish of Jewish kitchens; it has even been called “Jewish penicillin” and is used to treat and prevent illness. In American tradition, chicken soup was prepared using old hens that were too tough to be roasted or cooked but still made excellent soup. Unfortunately, the only soup that most Americans eat today is canned, highly processed, and devoid of nutrients.
Traditional cultures wisely practiced nose-to-tail eating and consumed all parts of the animal, including the skin, cartilage, tendons, and other gelatinous cuts of meat. This provided a balanced intake of all the amino acids necessary to build and maintain those same structures in the human body. Some anthropologists have even suggested that in some regions of the world, early humans were scavengers rather than hunters, using tools to crack open the bones of carcasses left by lions and other large predators to expose the rich bone marrow (3). Unfortunately, many modern cultures have lost the practice of whole-animal eating, and the old-age tradition of having a pot of broth constantly simmering on the hearth has been lost in favor of modern convenience, microwaves, and highly processed canned soups. Bringing bone broth back into the modern diet offers a simple and delicious means of obtaining the nutrition from parts of the animal that traditional cultures prized.
Bone broth: a nutrient gold mine
Bones contain an abundance of minerals as well as 17 different amino acids, many of which are found in broth as proteins like collagen and gelatin. Though the exact nutritional content varies based on the bones used, cooking time, and cooking method, the following nutrients are consistently found in most bone broths.
With 28 different types, collagen makes up about 30 percent of the protein in your body (4) and is the main component of connective tissues like cartilage, ligaments, tendons, bone, and skin. It is also present in the blood vessels, cornea, and lens of the eye. The name collagen comes from the Greek “kólla,” meaning “glue,” and the suffix “-gen,” which means “producing.” In fact, early glue was made from collagen more than 8,000 years ago, likely by boiling the skin and sinews of animals (5). In addition to providing structure, collagen also plays an important role in tissue development and regulation (6, 7).
When collagen is simmered, it forms gelatin. This hydrolysis of collagen is irreversible and results in the breakdown of long collagen protein fibrils into smaller protein peptides. However, its chemical composition is very similar to its parent molecule, collagen (8). Gelatin is what gives bone broth or stock its Jell-O-like consistency once it has cooled.
Glycosaminoglycans (GAGs) are complex carbohydrates that participate in many biological processes. They can attach to proteins in order to form proteoglycans, which are integral parts of connective tissue and synovial fluid, the lubricant that surrounds the joint (9). If the connective tissue, such as tendons, ligaments, and cartilage, is still attached, the bones in broth will provide our bodies with the whole spectrum of GAGs, including keratan sulfates, dermatan sulfates, chondroitin sulfates, and hyaluronic acid, which are the raw materials for skin, bone, and cartilage formation.
Glycine is an amino acid that makes up more than a third of collagen. It also acts as a neurotransmitter, binding to glycine receptors present throughout the nervous system and peripheral tissues. Signaling through this receptor is particularly important in mediating inhibitory neurotransmission in the brainstem and spinal cord (10, 11).
Proline is an amino acid that makes up about 17 percent of collagen. The addition of hydroxyl groups to proline significantly increases the stability of collagen and is essential to its structure. Though small amounts of proline can be manufactured in the body, evidence shows that adequate dietary proline is necessary to maintain an optimal level of proline in the body (12, 13). Proline is not typically thought of as a neurotransmitter, but it is able to weakly bind to glutamate receptors and glycine receptors (14).
Glutamine is yet another important amino acid found in bone broth and is the most abundant amino acid in the blood (15). It is one of the few amino acids that can directly cross the blood–brain barrier (16). Intestinal epithelial cells and activated immune cells eagerly consume glutamine for cellular energy (17, 18).
Inside the center cavity of the bone is the bone marrow, consisting of two types, red and yellow. Both types contain collagen. Red bone marrow is the site of manufacturing for new immune cells and red blood cells, while yellow marrow consists of healthy fats (19, 20). It is thought that important nutritional and immune support factors might be extracted from marrow during cooking, but the bioavailability of these factors has not been studied.
Bone is also full of minerals, including calcium, copper, iron, magnesium, manganese, phosphorus, potassium, sodium, and zinc (21). An acidic medium is necessary to extract these minerals from food. When making broth, always add a splash of vinegar or other acid in order to extract the most minerals from the bone.
Bone broth and your health
At this point, I hope you have a solid understanding of the components of bone broth. Now let’s get on to the health benefits!
Skin is composed of two layers, the epidermis and the dermis. The epidermis, or upper layer, is composed of keratinocytes and is largely responsible for skin barrier function. Underneath is the dermis, a dense matrix of collagen, along with some GAGs, that provides structural and nutritive support (22). Keratin, collagen, and GAGs are abundant in bone broth, particularly if the skin from the animal is included in the cooking process.
In a 2014 randomized and controlled trial, collagen consumption significantly improved skin elasticity and tended to improve skin moisture content (23). Collagen scaffolds are widely used in medical applications to promote tissue regeneration and heal wounds (24). One study in mice found that supplementing the diet with gelatin was able to protect against UV-induced skin damage (25). GAGs offer additional skin benefits. The GAG hyaluronic acid has been shown to promote skin cell proliferation and increase the presence of retinoic acid, which improves the skin’s hydration (26), and dermatan sulfate has been shown to aid in cell turnover and wound repair (27).
Metabolic and cardiovascular health
Remember glycine, an amino acid that is particularly abundant in bone broth? Glycine plays a role in blood sugar regulation by controlling gluconeogenesis, the production of glucose in the liver (28), and has even been suggested to counteract some of the negative effects of dietary fructose consumption (29). Glycine has also been shown to reduce the size of heart attacks (30).
Furthermore, glycine balances out methionine intake. Muscle meats and eggs are high in methionine, an amino acid that raises homocysteine levels in the blood. High homocysteine is a significant risk factor for serious diseases like heart disease, stroke, mental illness, and fractures and increases our need for homocysteine-neutralizing nutrients like vitamins B6, B12, folate, and choline (31). Those eating lots of animal protein need adequate glycine to balance out the methionine from meat, and you’ll get that from bone broth. For more information, check out Denise Minger’s awesome presentation in which she discusses this very issue.
Muscle and performance
Glycine is also important for the synthesis of hemoglobin and myoglobin, which transport oxygen throughout the blood and muscle tissue, respectively (32). Glycine also increases creatine levels, which leads to an increase in anaerobic (high-intensity) exercise capacity, and stimulates the secretion of human growth hormone (HGH), which may enhance muscle repair (33, 34, 35). Recent evidence suggests that proline may play a role in regulating the mTOR cellular signaling pathway, which integrates signals from nutrients, growth factors, stress factors, and cellular energy status to affect cell function and growth. Proline, together with other amino acids, activates mTOR, resulting in enhanced muscle protein synthesis (36).
Adenosine triphosphate (ATP) is the chemical form of energy in the body that can be used to perform work. Phosphorus is required for the formation of this compound, and ATP cannot be biologically active unless bound to a magnesium ion. Phosphorus deficiency has been shown to reduce muscle performance (37, 38). Both phosphorus and magnesium are present in bone broth in modest amounts.
Bones and joints
It should be pretty obvious that the best way to get the nutrients necessary to build bone is from bone itself! Drinking bone broth provides all of the raw material for building healthy bones: calcium, phosphorus, amino acids, and more. A deficiency of the raw materials for building bone can result in a number of different conditions. For example, osteoporosis is associated with reduced levels of collagen and calcium in the bones (39, 40). Of course, you’ll also need the nutrients required to support the building process, like vitamins D, K2, and C. (To learn more about building healthy bones and where to get these nutrients on a Paleo diet, check out this article.)
As for joint health, lubrication by GAGs is the key to a full range of motion, whereby part of one bone can slide smoothly and painlessly over part of another. Sure, you could buy expensive supplements containing glucosamine and chondroitin sulfate to keep your joints healthy, but why, when these and a host of other beneficial nutrients can easily be obtained from bone broth? After all, GAGs are not the only component of broth that improves joint health. Collagen supplementation has been shown to reduce joint pain in athletes (41).
A healthy colon contains a single tight layer of epithelial cells, a thick mucus layer, and a diverse collection of microbes. Microbial dysbiosis and a thinning of this mucus layer can quickly compromise the integrity of the epithelial barrier. Microbes and dietary proteins can then “leak” into the bloodstream and invoke an inflammatory response by the immune system. Lipopolysaccharide (LPS), a component of bacterial cell walls, stimulates a particularly robust immune response (42).
Bone broth is a staple of gut-healing diets, and rightfully so! Gelatin absorbs water and helps maintain the layer of mucus that keeps gut microbes away from the intestinal barrier. In a mouse model, gelatin supplementation reduced the severity of colitis by strengthening the mucus layer and altering gut microbiota composition (43). Gelatin and glycine have also been shown to reduce the inflammation caused by LPS (44, 45). Glycine has been shown to protect against gastric ulcers as well (46). Glutamine also helps maintain the integrity of the gut mucosa and intestinal barrier (47).
Bone broth has so many benefits to gut health that I had to make digestion its own section! Drinking broth with meals is an excellent way to aid digestion. Glycine stimulates the production of stomach acid, which is essential for the proper digestion of food (48). Low stomach acid (hypochlorhydria) is surprisingly common in developed countries and can lead to a number of health issues.
Glycine is also an important component of bile acid, which is released to aid in the digestion of fats in the small intestine (49). Bile acid is important for maintaining normal blood cholesterol levels. The presence of gelatin in the gut also draws fluid into the intestine, improving gut motility and supporting healthy bowel movements. Low blood levels of collagen have been associated with inflammatory bowel disease (50).
Detoxification, liver, and kidney health
Recently, there has been some concern regarding the lead toxicity of bone broth. However, the vitamins and minerals that are abundant in bone broth, and in Paleo diets in general, can protect against the harmful effects of toxins like lead. Glycine also stimulates production of glutathione, the body’s master antioxidant (51). In animal models, glycine has been shown to speed recovery from alcohol-induced fatty liver disease (52), protect liver cells against hypoxia (53), and improve survival after liver transplantation (54). In humans, glycine reduces oxidative stress in patients with metabolic syndrome (55).
Proline plays a role in apoptosis, the process by which the body breaks down old cells, clears up waste products, and recycles raw materials for use in healthy cells (56). Proline can scavenge free radicals, effectively acting as an antioxidant (57). Glutamine, on the other hand, acts as a nontoxic nitrogen transporter, carrying amine groups safely through the bloodstream to the kidney. In the kidney, the conversion of glutamine to glutamate regulates acid–base balance by producing ammonium (58).
Yes, bone broth may improve eye health. The cornea consists of three primary layers: an outer epithelial layer, a middle layer, and an inner endothelial layer. Hyaluronic acid stimulates proliferation of the epithelial cells that line the cornea (59) and is commonly used during eye surgery to help replace lost fluids (60). The middle, or stromal, layer is largely made of collagen, keratan sulfates, and chondroitin sulfates. Keratan sulfates have been shown to be essential to the transparency of the cornea (61), while chondroitin sulfate has been shown to influence the development of neural pathways in the retina (62). The amino acid glycine has also been shown to delay the progression of cataracts in a rat model of diabetes (63).
Numerous components of bone broth influence the nervous system. The healthy fats in bone broth, particularly if made with marrow bones, provide a source of fuel and raw material for the brain. After all, more than 60 percent of the human brain is composed of fat (64). Glycine has been shown to protect against neuronal death after ischemic stroke (65) and likely plays a pertinent role in the development of the brain in the womb and during the first few months after birth (66). Calcium is essential for nerve conduction. When a nerve cell is stimulated, the influx of calcium triggers neurotransmitter release, allowing the signal to be passed on to the next nerve cell. Calcium deficiency affects this transmission and can result in symptoms of depression, insomnia, and hyperactivity. Lastly, chondroitin sulfate plays an important role in regeneration and plasticity in the central nervous system (67), meaning it is essential for learning and memory.
Mood and sleep
Bone broth can also improve both mood and sleep. Glycine is an inhibitory neurotransmitter, meaning it can decrease anxiety, promote mental calmness, and help with sleep (68). One study found that three grams of glycine given to subjects before bedtime produced measurable improvements in sleep quality (69).
Unlike methionine, glycine does not compete with tryptophan for transport across the blood–brain barrier (70). Tryptophan is the precursor (raw material) for serotonin, a neurotransmitter that contributes to feelings of well-being. Serotonin, in turn, is a precursor to melatonin, a hormone that regulates sleep–wake cycles. This is why a diet that includes bone broth and fattier cuts of meat can help prevent the depression and insomnia that some people may experience when eating a diet high in methionine-rich lean meat and eggs.
While ancient folk wisdom suggests that bone broth can cure the common cold, modern science has confirmed that the components of bone broth do indeed influence the immune system. For example, glycine receptors have been identified on the outer surface of several different types of immune cells (71, 72). The effect is a dampening of the immune response, resulting in reduced inflammatory signaling molecules and oxidative stress that may reduce damage to lungs and other tissues (73). The GAG heparin sulfate has been shown to influence B cell function, T cell function, and macrophage activity (74).
Where to source bone broth
To summarize, bone broth has an incredible number of potential health benefits and is rooted in a long history of human use. It makes an excellent addition to any diet and can be used in a multitude of dishes. Bone broth can be made at home or it can be bought pre-made.
Homemade bone broth is simple to make. Ask your local farmers if they have soup bones, or roast a whole pastured chicken and save the bones for making broth. Chicken feet, chicken necks, calves’ feet, and marrow bones are particularly valuable additions to broth. You can find a good basic recipe over at the Weston A. Price Foundation website.
Pre-made bone broth is also a good option. Be sure to:
- Buy broth that is organic and made from pasture-raised animals or wild-caught fish (this minimizes the toxins and maximizes the nutrients you get from the bone broth).
- Avoid cans and other containers that contain bisphenol A (BPA), a potent endocrine disruptor, or other BPA substitutes.
However you choose to get your hands on this liquid gold, be sure to make bone broth a staple in your diet!