> Recommendations to Obtain Adequate Amount of Vitamin D.
> Sun exposure to the face, arms, hands, and legs without sunscreen for 5 to 30 minutes at least twice a week or more between the hours of 10 am and 4 pm
Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC8299926/
Now that's for most people: if you live in Alaska then during the winter maybe you need a litle more or something ... but the point is most people just need a little sun, < 30 minutes twice a week.
That study also claims 12-20ng/mL 25-hydroxyvitamin D is sufficient. My doctor says the post-COVID studies suggest 75ng/mL is closer to optimal, and <30ng/mL had been considered deficient for about a decade before COVID.
Personally I had no problem hitting 20ng/mL through sunlight alone and I'm pretty fair skinned but live somewhere sunny. But I haven't been able to get anywhere near 75ng/mL even when I've made an effort to increase vitamin D through supplements and exposure to the sun.
In Calgary, it's almost half the year that you basically cannot rely on the sun at all for vitamin D.