Questions abound this time of year about sun.
Should we avoid it entirely?
Chase it for vitamin D?
Only get exposure before 10 a.m. and after 6 p.m.?
Sometimes mere mortals feel our heads start to spin when it comes to this topic.
Good news: I did a deep dive so you don’t have to. As I dug in, I found there was so much to unpack that it’s become a three-part series.
Beyond Vitamin D
Sunlight does more than make vitamin D.
Exposure to UVA rays releases nitric oxide stored in your skin, which relaxes blood vessels and lowers blood pressure, independent of vitamin D status. It also boosts serotonin production.
One well-known Swedish study found sun avoidance was associated with a higher risk of death overall, comparable to smoking as a risk factor.
It’s worth noting that no major study has found sun exposure itself linked to higher all-cause mortality, despite its known skin cancer risk.
Finding the Sweet Spot
How much sun is enough?
For lighter skin tones, 10-20 minutes of midday sun (between 10 a.m. and 3 p.m.) on bare arms and legs is generally enough.
For darker skin tones, that range may be closer to 30-60 minutes.
Medium or olive skin tones typically fall somewhere in between, around 20-30 minutes.
Those are the ranges shown across research for both vitamin D and nitric oxide benefits.
(Be extra careful with the sensitive skin on your face. Always wear a hat to cover your face, neck, and ears, and use a low-toxicity sunscreen on your face. More on this next week!)
Midday exposure sounds counterintuitive because of all the bad press the sun has gotten for so long. That’s when UVB peaks, so you need less time to get the same benefit from more early morning or late afternoon light.
Know Your Skin Type
If you don’t know where you fall on the spectrum, take the Fitzpatrick Skin Type quiz below.
There’s also the newer Monk Skin Tone Scale, a 10-point visual matching tool built to better represent the full range of human skin tones.
Neither is perfect, but both can help if you’re unsure where you fall.
Dermatology is still working toward a tool that combines broad representation with precise UV guidance for more heavily pigmented skin tones.
Fitzpatrick Skin Type Quiz
https://www.skincancer.org/blog/are-you-at-risk-for-skin-cancer/
Monk Skin Tone Scale
https://monkscale.com/
One easy tool is to check the UV Index in your weather app before heading outside.
A UV Index of 2 or below generally means no protection is needed for most people. Above that, the “before 10 and after 6” guideline gets trickier because altitude, latitude, and the season all influence UV intensity.
No app handy?
Check your shadow.
If your shadow is longer than you are, UV is relatively low.
If your shadow is shorter than you are, you’re in peak sun exposure hours.
How do you know when you’ve had enough?
On fair or white skin, pinking means damage is already underway. This was a surprise to me because I always thought it was okay to get a little pink.
Both the vitamin D and nitric oxide pathways saturate well before that point.
Unfortunately, that cue is much weaker on darker skin because redness is harder to see, even after UV exposure has occurred. Going by the clock is the best practice.
Research also shows that regular, moderate sun exposure builds melanin over a season (photoadaptation).
By contrast, the “pale all winter, burn on weekends and vacation” pattern raises melanoma risk by around 60%, while regular, non-burning exposure does not. Several studies have even found regular sun exposure inversely associated with melanoma risk.
The one exception is squamous cell carcinoma, the most common and most treatable skin cancer. Chronic exposure does increase risk.
The clearest message across the research is this:
It’s the burning, not the sun, that does the damage.
Shade or Direct Sun?
Shade cuts UV. It doesn’t erase it.
About half of the UV that reaches you in full sun still reaches you in the shade because it scatters and reflects off water, sand, pavement, and snow.
Shade doesn’t eliminate the benefits. It simply slows them down.
You’ll need roughly twice as much time in the shade to get the same vitamin D and nitric oxide benefits as you would in direct sun.
Aging Skin
Aging skin makes less vitamin D per minute of sun exposure, and it’s also more reactive to the sun it gets.
More on both, and what to do about it, next week.
Your Move
Spend 10 to 15 minutes in the midday sun this week with bare arms and legs, while protecting your face with a hat and low-toxicity facial sunscreen.
Warmly,
Dr. Krista
Olive Says
Being conservative about sunbathing is hogwash. I do it all day long.
Fun fact: We older dogs need the warmth of the sun to help relieve arthritis, and natural light improves our mood just like it does for humans.