Emily Brown

Written by Emily Brown


75% of Runners are Vitamin D Deficient. Are You Getting Enough and How Can it Affect Your Training?

Research shows that 75% of runners are Vitamin D deficient. With the daylight dwindling, you're getting even less Vitamin D in the winter. Here's how low levels of Vitamin D can affect your training and overall health and recommendations to make sure you're getting enough.Vitamin D is an important component of a runner’s diet and recent research on the vitamin has concluded that it may be more significant for overall health than initially realized.

According to a March 2009 study in the Archives of Internal Medicine, more than three-quarters of adults are Vitamin D deficient. Furthermore, a 2008 study at the Cooper Clinic in Dallas found that 75 percent of runners averaging 20 miles a week have low vitamin D levels.

As a result, the recommended daily intake for vitamin D has increased in recent years, particularly for runners. Athletes should pay special attention to meeting these new requirements for vitamin D.

In this article, I am going to outline why Vitamin D is import your overall health and your performance as a runner. More importantly, I will provide daily recommendations as well as healthy sources to supplement your diet should you be falling short of the daily recommendation.

The Importance of Vitamin D for Runners

Vitamin D is best known for its role in maintaining bone health. It helps the body absorb calcium from food and supplements and helps maintain calcium homeostasis. If you suffer from chronic stress fractures, Vitamin D can be one of the supplements that decrease your risk of future stress fractures.

From a training perspective, a number of new studies show Vitamin D’s may provide significant performance benefits.

One study, published in February 2009 in The Journal of Clinical Endocrinology & Metabolism, concludes that adolescents with higher levels of vitamin D can jump higher, quicker, and with greater power than those with lower vitamin D levels.

A review in Molecular Aspects of Medicine in December 2008 shows that vitamin D increases the size of fast-twitch muscles and muscular strength.

Some research also shows low levels of vitamin D may increase risk for sports injuries, including stress fractures because the nutrient is so vital for bone health.

In addition, vitamin D plays a key role in a number of processes that are important for optimal athletic performance:

  • Muscle contraction– vitamin D is required for the activation of certain enzymes involved in muscle stimulation
  • Nerve stimulation– vitamin D is necessary for the nerves to carry messages between the brain and other parts of the body
  • Immune system– vitamin D helps activate and mediate the body’s immune function
  • Improved anti-inflammatory response– vitamin D plays a role in inhibiting proteins that trigger and inflammatory response in individuals with chronic inflammatory diseases (such as asthma and arthritis)

There are two bone conditions that can result from chronic deficiency of vitamin D: rickets in children and osteomalacia in adults. Even if dietary intake of calcium and phosphorous is adequate for bone health, sufficient vitamin D is necessary to absorb these minerals and without it, bone density and growth can be severely impacted.

How Much Vitamin D Do I Need?

The following are the newest recommendations for daily intake of vitamin D (issued by the Institute of Medicine in November 2010):

  • Children and Adults <70 years old: 600 IU (15 micrograms) per day
  • Adults 70 or older: 800 IU (20 micrograms per day)
  • Upper Limit (maximum safe intake): 4,000 IU (100 micrograms) per day

If you are afraid you are low in vitamin D, you can have your vitamin D status tested by measuring blood levels of 25-hydroxyvitamin D through a regular blood test performed by your doctor. He or she should then be able to determine if you are deficient, or at risk of becoming deficient, and recommend the proper supplement or dietary protocol. Typically, these blood tests are inexpensive (ranging between $30-$50) and can be combined with your iron test.

Where Can I Get Vitamin D?

Vitamin D is unique in that it can be obtained from foods but can also be synthesized by our own bodies through exposure to sunlight.

Vitamin D is one of four fat-soluble vitamins (A, D, E, and K) meaning that it needs adequate dietary fat to be absorbed. Therefore, fat-containing foods are often good sources of vitamin D. The following are some examples:

  • Fatty fish like salmon, tuna, catfish, sardines and mackerel; also fish liver oil
  • Mushrooms that have been exposed to ultraviolet light
  • Smaller amounts in foods like egg yolks and cheese
  • Fortified foods like milk, yogurt, breakfast cereals, orange juice and margarine (be sure to check the nutrition labels)

As mentioned previously, we can also synthesize vitamin D from exposure to sunlight. Normally 15 minutes of exposure for light-skinned individuals and 30 minutes for dark-skinned individuals is sufficient to meet daily needs for vitamin D. However, there are some limitations:

  • Indoor sun exposure (i.e. through the window) will not produce vitamin D. Furthermore, exposure is limited on cloudy days and when in the shade.
  • Overexposure of the skin to UV rays increases the risk for skin cancer. It is widely recommended to wear sunscreen to protect from skin cancer, but sunscreen also reduces the body’s ability to synthesize vitamin D from sunlight.
  • In the late fall and into the winter, the days become shorter and exposure to sunlight is further limited by cold weather and more clothing being worn when outside. Individuals living in the northern states are particularly at risk for insufficient vitamin D.

A final way to get vitamin D is through supplements. Vitamin D supplements can be found either on their own or combined with another product, usually calcium. Supplements are usually found in one of two forms: D2 (ergocalciferol) or D3 (cholecalciferol). D3 is the natural form of vitamin D that the body makes from sunlight and therefore is the more recommended form of vitamin D supplements, however both forms are sufficient at increasing vitamin D in the blood.

Final Notes on Vitamin D

It should be noted that it is possible to have too much vitamin D. It is highly unlikely to get too much vitamin D from food or sunlight; therefore vitamin D overdose is almost always associated with supplementation. Although vitamin D supplementation may be recommended, it is important to adhere to the recommendations and not exceed 4,000 IU (100 micrograms) per day for healthy adults.

Signs of vitamin D toxicity are often associated with increased blood levels of calcium and include: Nausea, vomiting, poor appetite, weight loss, constipation, weakness, confusion, disorientation, and problems with heart rhythm.

Too much of any good thing is a bad thing. Therefore it is important to maintain a healthy overall diet and only take supplements as recommended. Remember that many foods are already fortified with vitamins and minerals and many supplements contain more than one product. Be sure to check all of your supplement labels for vitamin and mineral overlaps to prevent overdosing.


NIH Office of Dietary Supplements, Vitamin D: http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

Aranow, C. Vitamin D and the immune system. J Investig Med. 2011;59(6):881-886.

National Jewish Health. “How vitamin D inhibits inflammation.” ScienceDaily, 23 Feb. 2012. Web. 1 Nov. 2012.

Free Strength Training Course

The Right Way to Add Strength Training To Your Running to Avoid Injury and Improve Performance

Here’s what we’ve got for you

How the “core” actually contributes to your running and which muscle groups are most important for staying injury-free

Which type of strength training exercises are most likely to directly improve your running performance (based on scientific research)

The 5 most common mistakes runners make with strength training (and how you can fix them)


Connect with Jeff Gaudette on Google+

9 Responses on “75% of Runners are Vitamin D Deficient. Are You Getting Enough and How Can it Affect Your Training?

  1. I ran in HS and realize now that very little was told to us about nutrition. I now run marathons, and recently realized how important iron is for runners. It made a huge difference in my training when I was more diligent about iron intake. In fact, I was astonished I had ran for so many years, and did not ever come across the fact that most runners were deficient in iron to the point it hampered their performance! How did I not know that?

    Anyway, this article was also quite insightful: Thank you!

    I wanted to ask: What do you, as a nutritionist and elite runner, think are some of the most overlooked vitamins, minerals, and other dietary problems with long-distance runners (especially young female runners who are thin but healthy weight)? Are there any other common deficiencies (like iron) that can be easily fixed through diet and/or supplementation to lead to improved performance and training in long distances?

  2. So so important! I take 5000 IU once a week (since it’s a storable vitamin) with a meal. If there is 1 pill I suggest someone takes, this one might be it.

    That, and I like the Thorne FX am/pm multi 🙂

    • Glad to hear that Kyle! You are doing the right thing. Multi vitamins are also important! Thanks for sharing your success story, and thanks for the recommendation of dosage 🙂

  3. I do “light running” about 3 times a week between 3-4 miles at a time. Recently I have had Achilles tightness in the first half mile of my run. After that it goes away and the tightness does appear again until my next run. So there is no lingering effect after the first half mile of tightness, until the next time I run again. Do you why this is happening?

  4. Hi, my work is mostly indoor. I work from home all the time. My age is 25, my B MI IS 24. The problem I am facing is my vitamin D3 count is only 03/100 ( yeah that much low!!!). Doctor asked me to take vitamin D3 doses through injection every week . And I am also having cholestrol 271, I have fatty Liver, high uric acid. Please suggest me right food which I can consume without increasing my cholestrol and fatty liver. Also should I do running or walking,I have this dilemma as my vitamin d is so low that I don’t want to fracture any bone.

Leave a Reply

Your email address will not be published. Required fields are marked *

Adding new comments is only available for RunnersConnect Insider members.

Already a member? Login here

Want to become an Insider for free? Register here