Collagen for Dogs – More Than Just a Protein Source?

Collagen is the most abundant protein in both humans and animals. Collagen for dogs constitutes a significant part of the connective tissue, including skin, tendons, bones, cartilage, and mucous membranes. It acts as a kind of “glue” that holds tissues together and provides structure, strength, and elasticity. So far, so good. But now it gets a bit more complicated. Collagen is not just one protein. Collagen is a whole family of proteins. There are at least 28 different types, but in dogs, it is mainly type I (1), II (2), and III (3) that are relevant. The different types of collagen have different functions and varying importance for the dog. Furthermore, they occur in different feed ingredients and supplements.

Type I strengthens and gives structure to bones, tendons, skin, and teeth, and is therefore particularly relevant in relation to bone health, wound healing, and skin elasticity. The function of collagen also reveals where this type typically occurs — namely in bones, tendons, skin, and teeth. Type I collagen is usually found in supplements made from bovine bones and hides (or bones and hides from similar large animals) as well as fish skin.

Type II provides support to joint cartilage and is therefore very relevant for a dog’s joint health. It is also this type of collagen that has been most studied in canine research. Type II collagen is found in joint cartilage and in the vitreous body of the eye and is typically present in supplements made from chicken cartilage or breastbone from larger animals, which naturally consist of large amounts of cartilage.

Type III is a protein that provides structure to, among other things, blood vessels and intestines. It is therefore relevant for the structure of the vessel walls and intestinal mucosa, and it is also here that this type of collagen is most abundant. If you wish to give a supplement with type III collagen, you should – as with type I collagen – choose one based on, for example, bovine bones or fish skin.

When dog owners choose to give their dog a collagen supplement, it is in most cases to do something beneficial for the dog’s joints. Either to prevent the dog from developing joint problems later on or because the dog has already developed a form of osteoarthritis, commonly known as degenerative joint disease. Osteoarthritis is one of the most common chronic diseases in dogs, characterized by the degeneration of joint cartilage, inflammation of the joint, and a gradual loss of mobility. Symptoms can range from morning stiffness to pronounced pain, reduced activity level, and decreased quality of life. Traditionally, osteoarthritis is treated with pain-relieving drugs (NSAIDs), weight loss, physiotherapy, and supplements such as glucosamine and chondroitin. But in recent years, collagen has entered the field as a promising joint supplement. Of the collagen types mentioned above, it is usually type II that occurs in supplements aimed at improving joint health.

To make the confusion complete, there is not only one kind of type II collagen. This type can occur in two different forms — in peptide form, i.e., hydrolyzed collagen, and in undenatured (non-hydrolyzed) form.

Hydrolyzed collagen – often called collagen peptides – consists of small peptide fragments that are easily absorbed in the intestine. These peptides can act as building blocks for the regeneration of collagen in joints and cartilage, but they can also have a signaling effect on cartilage cells and the immune system. And you’re probably thinking now: “Signaling effect? What does that mean?” And of course, I’ll explain.

When collagen is broken down into small peptides, these peptides can survive digestion and be absorbed intact in the intestine. Studies have shown that the peptides can be measured in the blood after ingestion – not only as individual amino acids (and thus the building blocks of peptides) but as small bioactive molecules. This means that they can reach tissues such as joints, skin, and intestines and act directly there.

Some collagen peptides can bind to receptors on cartilage cells (chondrocytes) in the joints. This stimulates the cells to produce new type II collagen and proteoglycans – the main building blocks of cartilage. At the same time, the enzymes that break down cartilage are inhibited. In this way, the peptides help maintain a healthy balance between the building and breakdown of joint cartilage.

Collagen peptides can also influence the immune system. Studies show that they can reduce the production of inflammatory cytokines (such as TNF-α and IL-6) and instead promote anti-inflammatory ones (such as IL-10). But back to the second of the two forms of type II collagen, namely undenatured type II collagen.

This type is not hydrolyzed but retains its three-dimensional structure. Undenatured type II collagen, which you find in various supplement products, is known as UC II®, a patented trademark. This is mentioned only so that you don’t wonder about the small ® in the name.

UC II® works on a different principle than hydrolyzed collagen: When dogs ingest small amounts of UC II®, the immune system can develop a form of oral tolerance toward the body’s own collagen in cartilage. When small amounts of UC II® are given orally, it is presented to immune cells in the lymphatic tissue of the intestine. Here, special regulatory T-cells are activated, which send “calming signals” to the rest of the immune system. The result is that the immune system becomes less likely to attack the body’s own collagen in the joint cartilage – and a dog with less pain and therefore greater mobility, as has also been demonstrated in studies with UC II®.

The intestine is not just a digestive organ. Its mucosa functions as an advanced barrier that must both allow the absorption of nutrients and at the same time protect against bacteria, toxins, and so-called allergens that can potentially provoke an allergic reaction. If the barrier is weakened – often referred to as “leaky gut” – it can lead to inflammation, immune reactions, and systemic diseases, i.e., diseases that affect the entire body.

In humans, there is growing interest in how collagen peptides can strengthen the intestinal mucosa. But what about dogs?

Several studies in mice and rats have shown that collagen peptides can increase the expression of so-called “tight junction proteins”, which keep intestinal cells in the mucosa tightly bound together, reduce inflammatory cytokines such as TNF-α and IL-6, and improve the intestinal wall structure in animal models with inflammatory bowel conditions. Studies in pigs have shown similar results: collagen supplements can improve intestinal wall structure, reduce diarrhea, and enhance nutrient absorption.

In the field of canine nutrition, there are no published clinical studies that directly examine the effect of collagen on the intestinal mucosa. Although it is so far only a hypothesis based on other animal models, it is nonetheless biologically plausible that collagen could strengthen the intestinal barrier in dogs as well.

As a reader of this blog, I am quite sure you’ve heard of “Bone Broth”. Bone Broth is made by long simmering of bones, cartilage, and often connective tissue from, for example, cattle, chicken, or fish. During this cooking process, collagen, various minerals, and amino acids – especially glycine, proline, and glutamine – are released. During the long cooking process, gelatin is also formed, which is partially hydrolyzed collagen. The actual content of each nutrient in the broth depends on the raw materials and preparation (including cooking time).

Although Bone Broth usually contains significantly smaller amounts of collagen compared to dietary supplements, it can still be a really good addition to the dog’s diet, as it not only has potential to some extent to strengthen bones, skin, connective tissue, intestinal mucosa, and joints. Bone Broth can also stimulate appetite in many dogs and significantly contribute to the dog’s fluid intake. And fluid is extremely important for healthy joints and a well-functioning intestinal mucosa. But that’s another story.

If you’ve made it this far, I’d like to congratulate you for having chewed through a very nerdy and complex topic – and say THANK YOU on behalf of your dog, because the time you’ve spent on this blog post is an investment in your dog’s health.

To summarize the key takeaways from this blog, here’s a “Important to remember” list:

• Collagen is not just one protein – there are many different types, of which types I, II, and III are particularly relevant for our dogs’ health.
• In relation to joint health, type II collagen is especially relevant. And here, both hydrolyzed collagen peptides and undenatured UC II® show good effects in canine studies.
• Collagen peptides act both as building blocks in joint cartilage and can stimulate cartilage cells to produce new collagen and influence the immune system by reducing the production of inflammatory cytokines.
• UC II® affects the immune system through oral tolerance and by activating regulatory T-cells.
• Studies in other animals show that collagen peptides may strengthen the intestinal barrier.
• Bone broth is a good supplement in a dog’s diet but cannot necessarily replace collagen from high-dose supplements if the dog has osteoarthritis.

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