I’m outside right now in a two piece and a hat. I never wear sunscreen.
What sunshine?
Actually, you need to get the early morning sun on your face and chest, which basically leaves out all of us who live in cold climates. I did it last summer, but now take Carlson’s Norwegian D-3 cod liver oil, pricey, but my very smart MD prescribes it, making it a deductible medical expense..
The skin makes vitamin d very efficiently. You make a lot exposing your arms.
People who are used to being in the sun can sunbathe for 10 minutes and make vitamin d that will last week or months.
In northern latitudes the Sun is often too low in the sky to get any vit D during Fall-Winter.
And generally the Sun needs to be at least 50 degrees high to get any. (The lower the Sun from your perspective, the more atmosphere there is between you and the Sun)
Some small studies show that Sun exposure provides more benefit that just producing Vit D, so it is better than taking the supplements, but for much of the year many have no choice but to take supplements if they want to keep their D levels high.