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  • Nicole Cozean, PT, DPT, WCS and Sharon Thompson

Vitamin D: Why the Sun Isn't Enough

What if everything we thought we knew about Vitamin D was wrong?

Most of us aren't too concerned about our Vitamin D levels, because after all, that's the one that comes from sunshine, right? We just have to wander outside for a few minutes a day and our bodies get a full dose? And most of us have seen it on our milk or orange juice labels, so we are thinking, Whew, at least that's one vitamin I don't have to worry about!

But shockingly, most of us are not getting enough just by being in the sun, and definitely not getting enough in our diet alonge. Vitamin D is not just important for good bone health. It is crucial for preventing chronic pain, improving sleep and improving quality of life. So how can we make sure we are getting enough?

Vitamin D and Pelvic Floor Dysfunction

The Importance of Vitamin D for Chronic Pain

But recent research is finding that Vitamin D is even more important than we had previously realized. Vitamin D deficiency is associated with many different types of chronic pain, including headaches, fibromyalgia, low back pain, knee pain, abdominal pain, rheumatoid arthritis, and nerve pain.

You Aren't Getting as Much Vitamin D as you Think

After reading about how important Vitamin D is, you might be thinking to yourself - "well, it's a good thing I'm getting plenty from the sun, right?" Well, the truth is a lot more complicated than that. Studies have found that 64% of us - nearly two in three - have suboptimal levels of Vitamin D, and nearly 40% are considered deficient. The statistics are even higher for African Americans (82%) and Latinos (69%).

Vitamin D and Pelvic Floor Dysfunction

So some really important things to know about getting enough Vitamin D:

  • We don't get Vitamin D in all seasons. The UVB rays that allow our skin to create Vitamin D are deflected by the atmosphere, so in the colder months - when the sun's rays have to travel through more of it to reach us - all of the UVB is deflected before reaching us. For example in Los Angeles and Atlanta, no UVB reaches us from September - early March. The further north (or south) of the equator you go, the larger the effect. So depending on where you live, you likely aren't getting any Vitamin D from the sun for nearly six months a year.

  • We don't get Vitamin D in the mornings or afternoons. Or on cloudy days. Or when we're driving. In the same way that we don't get UVB rays in the winter, the sun has to be above 45 degrees in the sky (90 degrees is straight above) for UVB to reach us. Clouds block UVB, and so does glass.

  • We block much of our skin with clothes or sunscreen. The UVB rays can't penetrate our clothing or sunscreen, so any skin that is covered with either can't receive sunlight to create Vitamin D. The studies that tell us we need 30 minutes a day of sunlight are generally assuming we're not wearing sunscreen and that we're in shorts and a tanktop - if you're slathered in sunscreen or dressed in long sleeves and slacks while taking a walk at lunch, only a fraction of your skin can create Vitamin D.

  • Production changes with skin color. Those with darker pigmentation take longer to be harmed by the sun's rays, but also take in less UVB rays that allow for Vitamin D product, so those with darker skin colors are at significantly higher risk of Vitamin D deficiency.

We've also become more aware of the dangers of excess exposure to sunlight, including skin damage and skin cancer, which has (rightfully) increased the use of suncreen and making us more aware of the dangers of being out in the middle of the day.

Balancing Risks

A major challenge with getting enough sun for Vitamin D production is that it also leaves us open to skin damage, including the increased risk of skin cancer. Some physicians feel that we've strayed too far in protecting ourselves from the sun, but the risk of skin cancer drives the recommendation to cover with sunscreen or clothing when out in the sun for prolonged periods.

Supplementing with Vitamin D

Fortunately, it's relatively easy and inexpensive to supplement with Vitamin D. Both Vitamin D2 and Vitamin D3 (the kind produced by the body) are available as supplements, and both increase the blood serum level of Vitamin D. In one uncontrolled study, adding Vitamin D decreased pain, increased sleep, and improved overall quality of life. Other studies have shown mixed results of Vitamin D supplementation, but no adverse events have been noted when the recommended dosage is followed.

If you're experiencing chronic pain, not outside in the middle of the day, or are concerned about a lack of Vitamin D through the winter, it may be advantageous to add a supplement. In our clinic we carry NOW Vitamin D-3 (2,000 IU), which is about $5 for a 3-month supply, but there are many different sources of both D2 and D3 to choose from. In winter, or if you believe you're not getting much Vitamin D from the sun at all, it may be advisable to increase to 5,000 IU when supplementing.

Blood Tests for Vitamin D Deficiency

While most of us can probably determine if we have Vitamin D deficiency just from our lifestyles, a blood test is the definitive way to diagnose a Vitamin D deficiency. Blood serum amounts for Vitamin D (25-hydroxyvitamin D) should be between 30 and 80 nanograms per ml. Below this level you would be considered Vitamin D deficient, while levels above 100 nanograms are not beneficial and eventually can result in toxicity.

We have a relatively good idea of how supplementing with Vitamin D affects the level in the blood. The two most common supplement amounts are 2,000 and 5,000 IUs. If you were getting no Vitamin D from the sun, 2,000 IUs would translate to a blood serum level of about 30 nanograms (on the low side of healthy), while 5,000 IUs would give a blood serum level of about 50 nanograms.

High-dosage, long-duration supplementing with Vitamin D should not be done without the specific recommendation and supervision of a doctor. While rare, taking more than 50,000 IUs per day (more than 10 times the normal amount) can result in toxicity and dangerous side effects.


More research is clearly needed in this area, but there seems to be a significant link between chronic pain and Vitamin D deficiency. We can't simply assume we're getting enough Vitamin D from the sun, so supplementing with a daily vitamin may be a good way to ensure adequate blood levels of Vitamin D. Talk to your physician to determine whether taking a Vitamin D supplement is a good idea for you.

Note: This article contains affiliate links to some of the products mentioned in the article. If you click on them the price you pay doesn't change, but we do get a small commission that goes into a coffee fund that gives us the caffeine to do more articles like these. As always, we only recommend products we truly believe in and that are supported by strong scientific evidence.

Additional Resources

Dr. Nicole Cozean is the founder of PelvicSanity physical therapy, Orange County's premier pelvic floor physical therapy clinic. One of only 270 PTs to be board-certified in the pelvic floor, and the first PT to serve on the ICA Board of Directors, Nicole is the author of the acclaimed and best-selling book The Interstitial Cystitis Solution (2016). She is an adjunct professor at her alma mater, Chapman University. The PelvicSanity blog focuses on presenting practical, positive information to help patients beyond the walls of Nicole's clinic.

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