The Surprising Truth About Vitamin D

Vitamin D is so hot right now. As the COVID-19 pandemic continues reports of Vitamin D boosting your immunity have made it a sought after supplement. As someone who spends a crazy amount of time outdoors, I hadn’t given Vitamin D much thought. Well, I recently had an awakening and the truth about vitamin D surprised me.

Learn more about Vitamin D, sunshine, sunscreen, and supplements.

diver stands in the blue water
Getting plenty of Vitamin D in the Sea of Cortez (all photos by Sara-Mai Conway)

My Personal Vitamin D Awakening

A few months back I noticed my hair was thinning. Not a big deal and nobody noticed, but I could see just a bit more of my scalp through my normally thick and wild curls.

Was it a sign of perimenopause? I had just turned 44. Was it stress? I’d been home for 3 months under quarantine. Was it thyroid issues? Hormones? Something else? My dermatologist suggested a blood test to rule out the worst. The results were a relief, but surprising. I’m deficient in Vitamin D!

Thanks to the novel coronavirus, I haven’t been surfing daily in Baja, and I’ve been at my desk far more than in the past. Still, I’m an outdoorsy gal who never once thought I’d be lacking in Vitamin D.

Turns out, what I thought I knew about this essential vitamin was wrong.

Why We Need Vitamin D

Vitamin D is essential. This means we cannot synthesize it on our own, and without it, things go horribly wrong. Vitamin D is actually not a vitamin per-se, but a prohormone, the precursor to a hormone.

Here’s just some of what Vitamin D does for us:

  • Regulates calcium in our bones
  • Prevents rickets, osteoporosis, and fractures
  • Keeps teeth strong and healthy
  • Helps regulate insulin to prevent diabetes
  • Influences the expression of genes to prevent cancer
  • Boosts our immune system and reduces risk of infection
  • Is associated with low blood pressure
  • Stimulates hair growth

Low levels of vitamin D are associated with almost every disease imaginable, including autoimmune disorders, cancer, cognitive diseases, diabetes, depression, heart disease, obesity, osteoporosis, and stroke.

How we Get Our Vitamin D

Sure, you can get Vitamin D from a few mushrooms and fatty fishes, but primarily, we get our Vitamin D from the sun, aka terrestrial ultraviolet radiation (UVR).

Sunshine provides us with both UVA and UVB radiation, and Vitamin D comes from the latter. When UVB rays hit our skin, Vitamin D is delivered to the liver then the kidneys. It eventually gets transformed into the active form we can use, which is not a vitamin at all, but a hormone.

Thanks, UVB rays! But wait, UVB rays are the very same ones that cause sunburn and skin cancer. So if you’re half-Irish and prone to burning like I am, you have a dilemma. Vitamin D deficiency or melanoma?

Dolphins Playing in the Sea of Cortez, Baja Sur

The Truth About Vitamin D and Sunscreen

Whether or not sunscreen prevents Vitamin D absorption is complicated. Sort of. Studies show if you’re avoiding a burn by hanging out in the shade, lathering on the sunscreen according to the directions, covering up with a wide brimmed hat and long-sleeved, long-legged clothing, you’re probably lacking in Vitamin D.

The good and bad news is…most people don’t use sunscreen according to the directions. When they do use sunscreen, they tend to spend extra time in the sun thanks to a false sense of security. Because of this, most studies show sunscreen doesn’t compromise Vitamin D absorption. Why? Because we’re doing it wrong. (NB: this ironically means sunscreen use is associated with higher incidents of sunburn)

In laboratory studies where sunscreen is applied correctly and conditions are controlled, sunscreen does in fact inhibit the synthesis of Vitamin D.

Those of us who are fair-skinned are well-trained to cover up and to cover-up well. Especially when on the water. This puts us at higher risk for a lack of Vitamin D.

The Truth About Vitamin D Supplements

Doctors will tell you the solution is to slather on the sunblock and compensate with a daily vitamin D pill. Yet science says this option fails.

Lack of vitamin D is highly correlated with disease and general unhealthiness, thus supplementation has been studied extensively. Just as often, supplementation has failed to demonstrate benefit. In 2019, one of the most rigorous studies to date found Vitamin D supplements have no impact on reducing rates of cancer, heart disease, or stroke.

Turns out vitamin D supplements have little or no benefit in otherwise healthy people. So what does this mean? Researchers guess it’s because low levels of Vitamin D are a result of these diseases, not the cause. Also, exposure to natural sunlight is far more essential than we’ve realized.

a dive boat parks at isla coronado
Dive Boat at Isla Coronado in the Sea of Cortez

Worship the Sun

Turns out the risk of being in the sun is far less terrible than the risk of skin cancer and Vitamin D-deficiency related diseases such as heart disease and cancer.

In 2019, Outside Magazine reported on the new skin care rebels who would rather we be in the sun than avoid it. These doctors and researchers found that melanoma, the most dangerous type of skin cancer, is associated less with long-term sun exposure, and more with intermittent sunburn, especially in our younger years.

In fact, those who are tanned and outdoors all the time not only have lower rates of melanoma, but they are 8 times less likely to die from it, because they’re way more healthy. A groundbreaking longitudinal study found sun avoiders were twice as likely to die (from any cause) than sun worshippers.

Sunlight is good for us. It’s not only a reliable source of Vitamin D, but it boosts our nitric oxide levels, lowers our blood pressures, produces the feel good hormone serotonin, and releases endorphins.

Sunlight is as essential for our wellbeing as sleep. It improves circadian rhythms, reduces inflammation, culls autoimmune response, lowers risk of breast and prostate cancer, and generally makes us happier.

A PSA on Vitamin D

So what’s a girl to do? Outside of the United States doctors are already recommending sunscreen be reserved for days when the UVB index is high, or for playtime on reflective surfaces such as water or snow. I’ll be taking my cue from those guys, and not the sunscreen lobby-influenced FDA.

Because my Vitamin D levels are already low, I’ll take the supplement just in case. Every day, I’ll make more of an effort to be out in the sunshine, skin exposed, for at least 15 minutes. I’ll save the sunscreen for when I’m on the water or exposed for 30 minutes or more.

I never thought I’d be at risk for low levels of Vitamin D. But consider this my PSA: if it can happen to me, it can happen to anyone. So take heed, take off your long-sleeved shirt, and worry less about time in the glorious sun.

Sara-Mai Conway is a yoga and meditation instructor with Baja Surf Yoga. Obviously, this article is not intended as medical advice, and as always, you should follow the advice of your own doctor. Also, relax and play outdoors!

3 thoughts on “The Surprising Truth About Vitamin D

  1. Hi Sara-Mai,

    I realise this post is old but as a surfer who recently suffered a minor stroke, I think one of the issues is that the amount of supplements that are recommended and the RDA of vitamin D are much lower than they should be. The main issue with too much Vitamin D is that you end up with too much calcium in your blood. If you reduce calcium intake (our calcium intake as a species was much lower before we started eating dairy products 2 – 3000 years ago) then you can have very high levels of vitamin D without adverse affect.

    1. Interesting! Thanks for the comment. Yes, seems like the powers that be are much more concerned we’re not getting enough calcium, versus vitamin D.

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