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How To Tell If You Need Vitamin D Supplementation

Why vitamin D is essential for runners and how you can add more to your diet.

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As a dietetics student, I believe that we should be able to meet most, if not all, of our micro and macronutrient needs from real food. I don’t take many supplements, preferring to eat a colorful, balanced diet.

That being said, one of the few things I do supplement is vitamin D.

After suffering from severe anxiety and generally feeling awful, my doctor discovered that I had a vitamin D deficiency. Research suggests that up to 50 percent of the world’s population could be vitamin D deficient.

Vitamin D helps the body absorb calcium and maintain its calcium homeostasis. This is particularly important for runners at risk of incurring stress fractures. Studies have also shown that people with higher levels of vitamin D can jump higher, quicker and with more power than those who are vitamin D deficient, since it boosts the fast-twitch muscles and general muscle strength.

Why Vitamin D Is Essential For Runners:

  • reduces risk of stress fractures
  • required for muscle contraction
  • helps boost the immune system
  • necessary for nerve stimulation, which enables the brain to send messages to other areas of the body
  • inhibits proteins that trigger inflammatory responses
  • can have protective elements on heart health
  • can improve mental health

Studies have shown a link between mental health and vitamin D, particularly in the prevention and treatment of depression. High doses have been found to ameliorate some symptoms of the disease. Vitamin D deficiency is also more prevalent in those that battle anxiety.

The best-known way people get vitamin D is through sunlight, which the body is able to synthesise for use (a daily does of 15 to 30 minutes of sun exposure is usually sufficient). Vitamin D is one of four essential fat-soluble vitamins, meaning we need to be eating enough dietary fat to absorb it. Dietary sources are available in fatty fish, mushrooms, eggs and fortified foods (like cereal).

In order to make sure your body absorbs vitamin D, you need to make sure you’re eating enough healthy dietary fat (found in foods like avocado, extra virgin olive oil, nuts and oily fish). Magnesium is also a factor in absorption, which I supplement regularly through magnesium baths after long runs but which can also be found in nuts, beans, leafy greens and whole grains (all of which should be part of a balanced diet).

As runners, most of us are outside a lot and therefore may not think we need to supplement our vitamin D intake. However, unless you’re running outside at midday in shorts and a tank top, you probably aren’t getting enough, especially during the winter months when most of our runs are completed in the dark or while covered with multiple layers of clothing.

While you might spend an hour or so outside each day for activities like your run or walk to work, you may not be hitting your daily vitamin D requirements during the colder and darker winter months. The National Health Service actually recommends that everyone in the United Kingdom considers taking a 10-migrogram daily supplement from October through March!

How To Tell If You’re Vitamin D Deficient

The best way to test for deficiency is through a blood test; however, daily symptoms you may begin to notice if you are deficient include muscle weakness, exhaustion, falling ill often, muscle pain, bone fractures and pain in the ribs, hips, pelvis, thighs and feet.

Pregnant and breastfeeding women are most at risk of being deficient, as are the elderly, vegans, vegetarians, people with darker skin pigmentation and those with other medical conditions, including renal and hepatic disease.

If you do decide to supplement your daily vitamin D intake, you’ll want to look for a high-quality supplement that provides your body with at least 10mcg.


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