Exploring the Impact of Vitamin D on Tendon Health

On today's episode, exploring the impact of vitamin D on tendon health. Welcome to the podcast that gives you the most up-to-date evidence-based information on P-HT rehab. My name is Brody, I am an online physio, but I've also managed to overcome my own battle with P-HT in the past, and now I've made my mission to give you all the resources you need to overcome this condition yourself. So with that, let's dive into today's episode. Thank you for joining me on today's episode. I have a research paper to cover. It's been in my back pocket for the last several months, and thought was nice to do on a solo episode rather than on the Run Smarter Podcast having episodes where I compile three to four different studies. I think this is a good topic on its own to learn more about vitamin D and explore whether it might be something that you test and trial and at least learn what the research currently says with the effects on tendon health. And before I get into this paper, I thought I would at least bring to you attention that I have done an earlier episode on vitamin C and tendon health. So I'll bring you up to speed on that, just give you a quick refresher, and then we'll dive into vitamin D. So as a quick refresher, vitamin C plays a key role in collagen synthesis. When we talk about breakdown of the body and build up of the body, we tend to use this term synthesis. You have muscle synthesis when you go to the gym, you work out your muscles, they break down a little bit, which is required. They then rebuild back stronger. Think of this process in the same way. Collagen synthesis, tendons are 80% collagen. And so we're mainly talking about the turnover of tendons, and vitamin C plays a key role in that turnover. And therefore, if we can enhance it, we are then theoretically helping both tendon recovery or injury and performance gains. So we learnt in that previous episode, the vitamin C acts as a co-factor, helping your body lay down strong and organized collagen. And when combined with other things like collagen, collagen supplementation, before exercise, it may actually help boost this collagen synthesis or the collagen production. This is a similar process that Keith Barre used. I interviewed him in earlier podcast episodes. He has this protocol of vitamin C and collagen taken together as a supplement. I want to say it was 15 grams of collagen, and they had it in a mixture of orange juice. So like a glass of orange juice, if not sure how much vitamin C was in that, but they took that before exercise, I think one hour before doing some tendon loading to then take advantage and boost this collagen synthesis. But now we're diving into vitamin D. So the title of this paper that I want to discuss is titled as the title of the podcast was exploring the impact of vitamin D on tendon health, a comprehensive review. It was released in 2024. And if you are a member of the AI assistant and have access to my database of papers, it is in the new releases folder. And it's in May 2025. That's obviously if you're listening to this at the time of recording. If it's several months from now, it will be in the archive papers. I do keep a track of nutrition as a key folder, but also tendon opathies as a key folder. So that paper will be in either of those if you want to go find it. And so let's explore this paper and what it says in the introduction. It says that tendon opathy can be viewed as a failure of the cell matrix to adapt to a variety of stresses as a result of an imbalance between matrix D generation and synthesis. Essentially the build up and breakdown of tendons as we do our workouts and we recover, do our workouts and recover. There's an imbalance there where there's more of a breakdown than a build up during the initial inflammatory process of a tendon opathy pro inflammatory cytokines and mediators are released leading to destruction and modification of this extra cellular matrix and a reduction in collagen synthesis. Vitamin D however, a pro hormone that major sources are of sun exposure and foods, especially dairy products is the essential precursor that classically regulates calcium and phosphate metabolism and it plays a key role in maintaining the balance between turnover and a healthy micro environment. This is a tricky introduction to this paper because they go into a ton of detail around all the little mechanisms, all the little processes that play and so I thought of throw it into chat GBT and come up with a bit of an analogy to help me and help you guys follow along with this process. So it says imagine your tendon is like a busy asphalt road that's constantly taking on traffic i.e. your daily movements and workouts. Other times small cracks start to form this is like a tendon opathy, a condition where the tendon becomes irritated and damaged from overuse. Now let's say a repair crew comes into fix those cracks but this crew is a bit chaotic at first they start tearing up parts of the road i.e. inflammation making things worse before they get better. These demolition workers represent the pro inflammatory chemicals. They break down the damaged material but can also destroy surrounding structures if left unchecked. Here is where vitamin D comes in. Think of vitamin D as the site manager who keeps the demolition crew in check, calls in more skilled builders to lay down new collagen and ensures everything is rebuilt in an organized long lasting way. Now if you're low in vitamin D that site manager never shows up. The repair crew keeps tearing things up but the rebuilding process stalls. Over time this leads to weaker repairs poor tendon healing and higher chances of re-entry. With that analogy out of the way hopefully you found it helpful let's go into the results of this study. The discovery from pht has never been simpler. If you've been struggling with this condition and you're not sure what to do next I've put together something to help. Think in the show notes is a 30 second question air literally just six multiple choice questions and based on your answers I'll point you towards the most effective next step for your situation because over the years I've created a range of resources from free education to structured self-guided programs all the way up to working with me directly all of which are aimed to strip away the mountain of misinformation about recovering from this diagnosis and taking out all the guesswork that leaves people like you overwhelmed. If that sounds helpful don't wait until the end of this episode click on the link in the show notes now and I'll guide you from there. I guess is a comprehensive review so they have to go looking for all the papers on this said topic so they search all the databases and they I guess sub categorize them into in vitro and in vivo studies this is very I guess early stages of investigating vitamin D and tendon health so there was a lot done in a dish or outside of the body which is what we call in vitro and then we have the in vivo studies which are within the creature within the organism being studied and most of these papers that they found were in animal studies and not in human studies but when going through this systematic process they ended up with 14 studies that are currently out there looking at vitamin D on tendon health and so let's go through the results now. First in vitro so the lab based cell studies so you might have some little tendon collagen things in a dish or in glass and they're just treating it to certain conditions and seeing how it behaves so researchers looked at how vitamin D affected damaged tendon cells like the ones you'd find in someone who's recovering from a tendon opathy and the key findings were vitamin D helped tendon cells recover after being damaged it boosted cell growth and increased production of collagen the strong protein that makes tendons resilient it reduced inflammation and oxidative stress which are two key barriers to healing these benefits were linked to vitamin D interacting with a specific cell receptor and regulating cell healing pathways like they mentioned ERK and P38 don't know what those pathways are but if you are that's what they're referring to so the bottom line with the in vitro studies vitamin D may help tendon cells bounce back and rebuild stronger when under stress especially after injury or overuse what about the in vivo studies so studies within the living creatures scientists gave rats a vitamin D deficiency and observed how their tendons related after injury and the key findings were rats with low vitamin D had weaker tendon repairs less collagen and poorer tissue structure when vitamin D levels were normal tendons healed faster stronger and more organized similar to how a well managed construction site runs the bottom line for runners if you're low in vitamin D your body may not repair tendons effectively putting you at higher risk of a chronic tendon opathy re-injury or slow healing if I'm looking and analyzing the results of that it seems to me that they're referring to if your levels are suboptimal bringing your levels back to normal will help heal this process I'm yet to say in this study if boosting If you are, if you are at optimal levels and you boost it yet again to something more optimal. Is there a more optimal level for these tendon processes or is there a cap that once you've reached a normal level and you try to supplement more and more and more that just has diminishing returns? I don't know. It's just the vibe I got with reading the summary of this or just maybe no studies have looked at adding in higher and higher vitamin D amounts and seeing what the effects are like there. So what should runners take from this? Even though these aren't human trials, bear that in mind, a consistent patent is clear. Vitamin D supports tendon recovery and a deficiency could delay healing and make tendon problems worse. If you're recovering from a tendon injury or training hard, checking and optimizing your vitamin D levels might help support your body's repair process. And so that's what we've gathered from this particular paper. And I guess I thought it might be helpful if we layer in some additional information around vitamin D levels getting tested and that sort of stuff just to make this a little bit more practical for you. Again, I asked chat GPT to come up with some key takeaways. And in relation to testing, how can we test if you are deficient in vitamin D? It says to ask your GP or sports doctor for a special blood test. It's a 25 hydrooxy vitamin D blood test and this is the most accurate way to measure your vitamin D status. What is optimal in terms of our levels? They said many experts agree that 50 to 75 nanomoles is an adequate level for athletes. And injury prevention is even higher than that. It's 75 to 125, which is often considered optimal. If you are below 50 nanomoles per liter, this is considered a deficit or deficient and may negatively impact healing, bones, strength, and muscle function. How do we get vitamin D? Well, we naturally get it with sun exposure. I usually think about it in terms of vitamin D. Daylight vitamin D is the sun. So sun exposure. And they say 10 to 30 minutes per day depending on your skin type. If your darker skin, it's going to be harder to absorb vitamin D from sunlight. The location where you're placed in the world but also where it's located on your body. Aim for some skin exposure without sunscreen on your arms and legs during the mid morning or mid afternoon. Be careful like the mid day because that's when harsh UV levels. If anyone's in Australia, you're very familiar with the harsh UV levels. But you don't have to get it from sunlight. You also get it from food sources, fatty fish, salmon, sardines, eggs, egg yolks, and fortified foods like cereals and plant milks. But sometimes natural sources alone aren't enough, especially in winter for some people, people who are darker skin, people who constantly work indoors. I know a lot of people in the UK talk about how they don't get a lot of sunlight some parts of the year. So always something to be mindful of, which leads you into should you supplement should you supplement with vitamin D. And I guess it just depends on your current levels. How much sun exposure you get. Maybe getting a blood test and seeing if you are low. If you are low and at risk, it's common to assume obviously listen to your GP and health practitioner about supplementing, but it seems like a supplementation would be a good idea. Chat GBT says it's commonly safe to start at 1 to 2000 I use per day. A lot of the I guess liquid based vitamin D supplements, usually one drop is 1000 I use in the day. And so just one or two drops of that. If severely deficient, higher doses may be prescribed temporarily. I just listen to a podcast for those who are familiar with Ronda Fitzpatrick, very big vitamin D and omega three advocate done a lot of studies on those things. She was just saying that 4000 I use per day is what's recommended for most. Obviously individual results vary. And then I know I take vitamin D. I take about 4000 to 5000 I use every second day, but it also has K2 in it. And if you're supplementing above 1 to 2000 I use per day for a long time, especially with calcium, pairing it with vitamin K2 can be advised. From what I've gathered from my research, K2 helps direct the calcium into the bones. And so if you are wondering about bone health and bone density and all those other things, if you are taking all this vitamin D, vitamin D does help with bone health as well. And you're taking it with calcium and you want to direct that calcium through the bone rather than just having it circulate anyway. That's where the K2 pairing the K2 can help to the best of my knowledge. And so hopefully found this quick episode quite informative. Maybe it's help you learn more about vitamin D and the mechanisms at play. And then maybe have you investigating if you are getting adequate amounts, if not maybe investigating whether your amounts are adequate or not. And who knows maybe is a game changer for you in your tendon recovery. If you are looking for more PhD resources, then check out my website link in the show notes. There you will find my free PhD five day course, other online content and ways you can personally connect with me, including a free 20 minute injury chat to discuss your current rehab and any tweaks you might need to make. While done for taking active role in your rehab, find the link to content like this and together we can start ticking off all of your rehab goals and finally overcome your PhD.