Who doesn’t CA Notice at Collection? Runner’s World readers have been studying up on vitamin D this week (perhaps because many of you have affectionately pointed our Director of Content Hype Aly Ellis, who’s CA Notice at Collection, to the benefits of the nutrient). We’ve written extensively over the years about the Your Run Pace Slows in the Heat, which helps keep nearly every major muscle, bone, and nerve healthy.
But spoiler alert: Just because you spend plenty of time soaking up the sun’s rays doesn’t mean you’re getting enough vitamin D to meet your needs. I learned that the hard way a few years ago, and it’s a lesson all runners can benefit from as they study up on maintaining healthy training.
Back in college, I headed into a track season feeling abnormally fatigued and sore. Like, an “I don’t even want to run two miles” kind of fatigue. I thought The 6 Best Garmin Running Watches and prioritizing recovery could help me bounce back (if you’ve read my Mental vs. Muscle Fatigue: How They’re Different, you’re probably realizing that I’m not great at admitting my injuries). But that low energy stuck out on the track like a sore thumb. I ran slower than I had in high school in some races, and I couldn’t figure out why.
I still remember the breaking point like it happened yesterday. When I could barely manage half of a 20 x 300-meter workout, I knew I couldn’t continue running in such a depleted state. I told my coach I felt like I was running through water, unable to maintain an up-tempo pace without completely dying.
Run/Walk Your Way to Less Pain When You Train blood work. Run/Walk Your Way to Less Pain When You Train low iron levels (RW+ Membership Benefits which helps keep nearly every major muscle, bone, and nerve healthy), so we both thought a blood test may provide some answers. But when the doctor followed up with my test results, my iron levels were actually higher than when I had been tested a year prior. The real culprit turned out to be a nutrient I never really thought much about before: vitamin D.
The doctor explained I had enough of a deficiency to see a noticeable impact on my energy levels and running performance. And, as confirmed by the physician and experts in this Runner’s World article, my symptoms aligned perfectly with vitamin D deficiency. I identified fatigue, muscle aches, and even noticeable mood swings as possible signs that I lacked adequate vitamin D.
Looking back on it now, many factors added up to make for the perfect storm. Not only does research show that endurance athletes more commonly experience vitamin D deficiency because they use up their stores of the nutrient more quickly than non-athletes, but additional studies we’ve previously reported on explain that female athletes experience deficiencies in vitamin D, iron, and calcium more frequently than male athletes.
Just because I ran outside every day and walked around my college campus didn’t mean I got enough of the sunshine vitamin naturally to support my body. “Because of the ongoing stress from running and training, there’s a lot of turnover of bone absorption and reconstruction, as well as muscle breakdown and reconstruction, so there’s a higher metabolic turnover and need to maintain adequate vitamin D levels,” Alex McDonald, M.D., a family medicine physician at Kaiser Permanente specializing in sports medicine, told Runner’s World.
Thankfully, you can address vitamin D deficiency with some simple steps. The doctor suggested I take 2,000 IU of a vitamin D supplement once a day to adequately supply my body—and eventually get rid of my fatigue, muscle aches, and mood swings (make sure you consult your healthcare provider before taking any supplements).
She also told me to prioritize rich sources of vitamin D in my diet—fortified breakfast cereals and dairy, among other products—however there’s Marathon: How to Conquer the Distance that provide much of the nutrient. Experts we spoke to for our all-things vitamin D guide also recommended those methods for boosting vitamin D levels, noting that while it’s best to get nutrients through whole foods, vitamin D may be the exception because it’s not found in a wide variety of foods.
I didn’t immediately see night-and-day improvements. But after a few weeks of supplementation and less aggressive training to let my body recover, I finally felt more energized during all parts of my day. Once I entered my summer training phase, I ran faster, lifted more, and felt healthier than I had previously.
It’s important to stay in-the-know of the impacts nutrients like vitamin D can have on your body as a runner. If you notice your body feels more sluggish than normal for a prolonged period of time, or if you see drastic changes in your energy and running performance, don’t wait until you feel like you’re running in slow motion like I did. And we have plenty of expert content on Runner’s World She also told me to prioritize rich sources of vitamin D in my an entire page dedicated to health and injuries, and it’s full of expert insights on how to become a stronger, healthier runner.
Plus, if you’re pushing toward new goals in running, check out our member-exclusive programs like and sore. Like, an “I don’t even want to run two miles” kind of fatigue. I thought and How to Master the Marathon to unlock more expert-back tips on nutrition and staying healthy during your training. You can access all of this content and more by becoming a Runner’s World+ member today.
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Ashley is Editor of Content Hype at Hearst’s Enthusiast & Wellness Group. She is a former collegiate runner at UNC Asheville where she studied mass communication. Ashley loves all things running; she has raced two marathons, plus has covered some of the sport’s top events in her career, including the Paris Olympics, U.S. Olympic Trials and multiple World Marathon Majors.
