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Training and COVID-19: Why triathletes should take a vitamin D supplement

New research is showing a link between vitamin D deficiency and severe COVID-19 infections.

As triathletes, it’s important that we have strong immune systems. You can’t stay consistent in your training if you’re constantly being sidelined by colds and flu. In the midst of the COVID-19 pandemic, immunity has become an even higher priority. Dietary supplements are one strategy that some triathletes may use to bolster their immune systems, and in the age of COVID-19 one vitamin has risen to the top: vitamin D.

Earlier this year, a literature review revealed that cardiovascular fitness could lower your risk for severe COVID-19, and endurance athletes everywhere breathed a collective sigh of relief. With that in mind, lots of people began lacing up their sneakers and getting out for some fresh air. That being said, there is a point of diminishing returns in relation to training and immunity. Over the last couple of decades, several studies have indicated that high-volume running (and triathlon training), in particular marathon training, could actually have a negative effect on your immune system.

Related: Strava sees boom in global exercise during COVID-19 pandemic

In fact, a 2007 study found that following long, hard bouts of running, there is an “open window” of immune dysfunction. The researchers determined that this could last anywhere from three to 72 hours, during which time you are more susceptible to viruses and bacteria.

Another study in 2013 concluded that in athletes, symptoms of respiratory infection tend to cluster around competitions. Not surprisingly, the authors noted that this can impair performance. They also noted that athletes can implement behavioural, nutritional, and training strategies to lower their risk of infections. This includes getting adequate sleep, frequent handwashing, and keeping their distance from those who are sick… sound familiar?

This year, of course, endurance athletes have one more thing to worry about: COVID-19. While a healthy diet and proper sleep can help bolster your immune system, some triathletes may also want to consider supplementation for further immune support. More specifically, a vitamin D supplement may lower your risk for colds, flus, and severe COVID-19 infection.

The role of vitamin D in the prevention and treatment of COVID-19 is still under review, but several studies have found a link between deficiency in the vitamin and the novel coronavirus. A study published in October 2020 in The Journal of Clinical Endocrinology and Metabolism found that 82 percent of hospitalized COVID-19 patients were vitamin D deficient.

Scientists are still investigating the role of vitamin D and immune function, but it appears that the active form of the vitamin helps prevent an overactive immune response that can damage your vital organs. Additionally, it boosts your immune cells’ production of microbe-fighting proteins.

It’s important to note that vitamin D will not prevent you from contracting COVID-19. What it can do is prime your immune system so that you’re less likely to experience severe symptoms if you come down with the virus.

What does this mean for triathletes? If you’re not already taking a vitamin D supplement, you may want to consider it. This is especially true if you’re planning on spending your lockdown logging lots of running and cycling miles. Of course, you should never add a new supplement into your diet without speaking with a health professional first, especially if you’re already taking other supplements or medications.

Most importantly, the best thing you can do is follow the advice of our public health officials. That means washing your hands, wearing your mask, and keeping your distance from others. Knocking out a solo long run or ride might be a challenge, but it will keep all of us safer until we can run together again.

This story originally appeared on the Canadian Running Magazine website.