Sun exposure and vitamin D
tl;dr Low levels of vitamin D are linked to numerous adverse health outcomes. 5-30 minutes of sun exposure per day without sunscreen is optimal for vitamin D synthesis in the spring and summer months. Talk to your doctor about maintaining stable vitamin D levels throughout the year.
This is part 3 of a 3-part series on light and the body.
Your body on natural light: energy, mood and more
Light and sleep
Sun exposure and vitamin D
Quick story
It was sometime between 2000 and 2013. My primary care doctor was a nurse practitioner at a gynecology practice in San Francisco. I saw her for years. I thought she was great.
One visit, she told me there was information surfacing that vitamin D was (more) important (than previously recognized) for health. She suggested a supplement. I was dubious.
As I recall, I ignored the recommendation. In hindsight, I think this GYN practice was ahead of its time. That’s pretty cool.
Tokyo, Japan
Plants need sun to thrive. We’re no different. Natural light is a critical component of optimal health.
“Conversations about the role of sunshine and vitamin D supplementation is vital to optimizing health outcomes.”
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Is there a happy medium somewhere between overexposure and fear of the sun?
Strawberries, Fujikawaguchiko, Japan
Why is vitamin D important?
Vitamin D is a nutrient your body needs for building and maintaining healthy bones.
Vitamin D also regulates many other cellular functions in your body.
Its anti-inflammatory, antioxidant and neuroprotective properties support immune health, muscle function and brain cell activity.
[source]
“Low vitamin D levels are linked to an increased risk of numerous chronic conditions including hypertension, diabetes, myocardial infarctions, or stroke as well as pre-eclampsia, gestational diabetes, and other adverse pregnancy outcomes.”
[source]
Bamboo forest, Kyoto, Japan
Give me some specifics
Cognitive health
Research shows that low levels of vitamin D in the blood are associated with cognitive decline.
Multiple sclerosis
Research suggests that long-term vitamin D supplementation reduces the risk of multiple sclerosis.
Osteoporosis
Studies suggest that people who get enough vitamin D and calcium in their diets can slow bone mineral loss, help prevent osteoporosis and reduce bone fractures.
[source]
Vitamin D supplements
How do we get vitamin D?
“Sunlight is unarguably the most optimal way to obtain vitamin D plus numerous other benefits. It is free, and our body is able to self-regulate the amount of vitamin D it receives, making vitamin D toxicity improbable.”
[source]
Your body makes vitamin D when direct sunlight converts a chemical in your skin into an active form of the vitamin (calciferol).
The amount of vitamin D your skin makes depends on many factors, including the time of day, season, latitude and your skin pigmentation.
Depending on where you live, vitamin D production might decrease or be completely absent during the winter months.
Sunscreen can decrease vitamin D production.
Vitamin D isn't found naturally in many foods. Foods containing vitamin D have typically been fortified in the production process.
Supplementation. Talk to your doctor.
[source]
Kyoto, Japan
Let’s get practical
“It is optimal to have sun exposure for 5 to 30 minutes a day, most days a week, without sunscreen, as SPF ≤8 may block the body’s ability to absorb the UVB rays to effectively make vitamin D.”
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“A study done in Valencia, Spain, measured the amount of sunlight necessary to produce a sufficient amount of vitamin D in those with lighter skin.
In spring and summer,
25 percent of the body (the hands, face, neck and arms) is exposed to the sun, and in these seasons, about 8 to 10 minutes of sun exposure at noon produces the recommended amount of vitamin D.
In the winter,
only 10 percent of the body is exposed, and nearly 2 hours of sun exposure at noon is needed to produce a sufficient amount of vitamin D.”
[source]
My approach
I get outside every morning with sunscreen on my face and neck, not on my arms or legs. I also supplement a few times a week with 1,000 mg of D3.
Bloodwork
My last vitamin D test result was 44, with a range of 30-100. That was May 2023.
How much should we worry about the risk of skin cancer from 5 to 30 minutes of unprotected sun exposure per day?
There’s a lot of press these days about sun exposure as harmful. It’s understandable, but consider that we don’t always get all sides of the story — at least not at the same time — in the popular press. No wonder we’re confused about what’s best.
Global skin cancer deaths are a fraction of other disease rates, including other cancers.
“…excessive UVR exposure accounts for only 0.1% of the total global burden of disease in disability-adjusted life years…”
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59,000 people died of skin cancer in 2022 vs. 1.8 million of lung cancer and nearly 1 million (904,000) of colon cancer.
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If you have a history of skin cancer, of course, talk to your doctor about the risk of 5-30 minutes of sun exposure for skin cancer, as compared to the health benefits of sun exposure and vitamin D synthesis.
If your doctor is not testing your vitamin D levels, consider asking them why (not)?
Kyoto, Japan. Is that a tan on my face? No. It’s beta carotene.
How do you feel about being in the sun? Let me know! ☀️
Thanks for reading!
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