I was going to a "wholistic" chiropractic health nut a few years ago (it did help with debilitating siatica) and her recommendation was full-body exposure to mid-day sun for 15 minutes. I laughed and asked her if she would post bail for me.
I think people don’t need a lot of sun exposure to have a good vitamin d level. I guess a few minutes on arms and maybe legs, 3 days per week, is enough.