Ever felt totally wiped out during your runs, no matter how much you train?
I’ve been there—sore muscles, heavy legs, and energy that disappears way too fast.
I kept pushing through, but something felt off. Then a friend suggested checking my Vitamin D, and it changed everything.
Vitamin D isn’t just about bones—it’s a key player for muscle strength, recovery, and keeping your energy up.
If your runs feel harder than they should or your body’s not bouncing back, Vitamin D might be what’s missing.
Let me explain why it matters so much for runners—and how you can make sure you’re getting enough.
What is Vitamin D?
You probably know Vitamin D as the “sunshine vitamin” because our bodies make it when we get sunlight. But Vitamin D isn’t just any vitamin—it’s a hormone that does a lot more than you think.
It helps your body absorb calcium for strong bones, but it’s also key for your muscles, immune system, and even your mood.
There are two types of Vitamin D you need to know about:
- Vitamin D2, found in some plants and mushrooms, but not as effective in your body.
- Vitamin D3, the most active form, made when your skin gets sun. You can also find it in fatty fish, egg yolks, and fortified dairy.
Most of us need Vitamin D3 to keep our levels healthy. Without enough, our running performance suffers—and we don’t want that!
How Vitamin D Affected My Winter Slump and Knee Pain
It wasn’t just the tiredness on my runs that gave it away. After a long, dreary winter with little sunlight, I felt completely drained. I was struggling through easy runs, like I was running through mud.
But what really caught my attention were my knees, which had been fine until then. They suddenly felt stiff and sore, even off the run. It was a constant ache that wouldn’t fade, no matter how much I rested or foam rolled.
I got a blood test, and to my surprise, my Vitamin D levels were dangerously low. Once I started taking supplements and getting more sun, my knee pain faded, and my energy came back.
This made me realize just how important Vitamin D is for performance and recovery, especially during those long winter months with no sun.
How Vitamin D Affects Recovery
When you’re running, your body takes a lot of impact—especially when you’re logging those long miles or pushing through tough terrain. This constant pressure on your bones increases the risk of injuries like stress fractures.
And guess what? Vitamin D plays a major role in bone health by helping your body absorb calcium.
Without enough Vitamin D, you’re more likely to face stress fractures or other bone injuries.
Supporting the Science
My experience wasn’t the only thing that showed me how important Vitamin D is for runners. Studies show Vitamin D plays a key role in muscle function and recovery.
The American College of Foot and Ankle Surgeons found that 80% of runners with stress fractures had low Vitamin D levels. This was a game-changer for me since I had been dealing with knee pain that only got better after I upped my Vitamin D intake.
It confirmed what I already suspected: Vitamin D is essential for faster recovery and injury prevention, not just bone health.
The Link Between Vitamin D and Muscle Function
Vitamin D is not only great for your bones—it’s crucial for your muscles, too. It helps muscles contract properly, prevents cramps, and speeds up recovery after tough workouts.
After paying attention to my Vitamin D intake, I felt a major difference in muscle recovery. My muscles weren’t as sore after long runs, and cramps during intervals became less frequent.
I used to wake up stiff and sore, but once I boosted my Vitamin D, that became a rare occurrence. My runs felt smoother, and I had more energy to push through each mile.
Vitamin D and Immune System Boost
As runners, we push our bodies hard, especially during the colder months when training picks up. The last thing you want is to catch a cold and lose training days.
That’s where Vitamin D comes in. It helps regulate your immune system, so you stay strong and healthy during tough training.
I can’t tell you how many times I’ve seen runners, myself included, get sidelined by a cold mid-training block.
But when I kept my Vitamin D levels up, I stayed healthier and didn’t have to stress about getting sick.
How Does Vitamin D Impact Performance?
I’ve already eluded into why Vitamin D is crucial for bones, muscles, and immunity, but what about your performance? Let’s talk about how it impacts your running.
Vitamin D can boost muscle strength, help you run faster, and increase endurance.
Once I focused on my Vitamin D intake, I noticed I could run faster and with less fatigue. It felt like I’d found the missing piece—suddenly, I wasn’t just completing runs, I was excelling.
Symptoms of Vitamin D Deficiency: Are You at Risk?
If you’re not sure whether you’re low on Vitamin D, here are some common signs to look out for:
- Fatigue: Feeling drained? Low Vitamin D can leave you tired, even after a good night’s sleep.
- Muscle Weakness: Struggling to keep your muscles strong or noticing more soreness after runs? It could be a sign of Vitamin D deficiency.
- Bone Pain: Pain in your joints or bones, especially after long runs, might mean your Vitamin D is low.
- Frequent Illness: Catching colds often? Low Vitamin D might be affecting your immune system.
If you’re facing similar issues, it might not just be about your training intensity or mileage. It could be a sign that your Vitamin D is low, and fixing that could be the key to feeling better.
How to Get Enough Vitamin D: Sun, Food, and Supplements
Now that we know why Vitamin D is so important for runners, let’s talk about how to get enough.
Get Some Sun: The Natural Source
The best way to get Vitamin D is by soaking up some sun. Most people need 15-30 minutes of sun a few times a week for a good dose of Vitamin D. But how much you need depends on your skin tone, where you live, and the season. If you live in a place with long winters or have darker skin, you might need more sun.
Even in winter, getting outside during the day, even on cloudy days, can help boost your Vitamin D. I try to get some midday sun whenever I can, and it’s made a real difference in how I feel on my runs.
If you’re running early or late when the sun’s weak, try to catch some sun at lunchtime to make up for it.
Eat Vitamin D-Rich Foods: Fuel Your Body Right
Sunlight isn’t always enough—especially if you’re logging early mornings, running indoors, or living somewhere cloudy. That’s where food comes in.
Fatty fish like salmon, mackerel, and sardines are some of the best sources. I try to get a couple of servings a week, whether grilled, baked, or fresh sashimi when I’m in Bali. If you’re not big on fish, fortified foods like milk, orange juice, and cereals can help fill the gap.
Egg yolks also contain some Vitamin D, so don’t skip your morning eggs—they’re small but mighty.
Consider Supplements: Your Backup Plan
Sometimes life gets in the way. You miss your sun time, the fish delivery is late, or the rainy season drags on. When that happens, I don’t hesitate to take a Vitamin D supplement, especially during the darker months.
Most runners I know test their Vitamin D levels once a year to make sure they’re in the right range. If you decide to go the supplement route, aim for Vitamin D3—it’s the form your body absorbs best.
Remember: More isn’t always better. Too much Vitamin D can cause issues, so stick to recommended doses or chat with your doc.
The Bottom Line
Vitamin D isn’t just about bones—it’s a hidden key to feeling strong, recovering faster, and running better. Getting enough sun, eating smart, and supplementing wisely are your best bets.
Try to make a little Vitamin D a regular part of your runner’s routine—it’s one of those small things that pays big dividends over time.