There’s two main needs from sunlight, as far as I know, (for now)
There’s the sunlight that falls on your skin
And sunlight that falls on your eyes
The former is mainly thought to be for vitamin D production, but there’s probably more to it than just vitamin D.
The latter is for circadian rhythm entrainment(resetting your body’s internal clock), but there’s probably also an effect on vision and posture because looking at the sun means looking at the horizon, which takes us away from the excessively near focused eyes of modern lifestyle
Sunlight on your skin needs to have UV light in it.
Sunlight that falls on your eyes directly should have as little UV in it as possible(should be predominantly infra red
Coming to the prescription
Don’t ask for a randomised control trial. I’m just posting what I’m doing. You’ll have to try it for yourself and figure out what works best for you.
2-3 minutes of direct sunlight on your skin(bare torso) daily in between 10am and 4pm if you’re in the tropics. If you’ve only got the time to do this once weekly, aim for 15 minutes. But build up your skin’s tolerance to bright sunlight gradually. Getting a sun burn is a great way to increase your risk of skin cancer. Getting a high volume of UV light on your skin, that you’re unaccustomed to, can also cause a transient immune suppression. So start off with 2 minutes and build up by a minute every week, if you’re trying a weekly dose
7 minutes of direct early morning sunlight, when you’re looking at the sun. This ABSOLUTELY HAS TO BE EARLIER THAN 6.30AM. or later than 6pm. Or both, if you want to go the extra mile.
Any deviation from this time frame, will probably result in blindness or partial retinal damage. Again, trick is to build up slow.
Start with 30 seconds on, 30 seconds off for a total of 3 minutes in the beginning. Since you’re just standing there, staring at the sun, you might as well meditate. The term for this practice is sun gazing. You should probably do a lot more reading on it before you decide to practice that.
Other parts to the prescription
– minimise exposure to artificial light.
– minimise exposure to electronic screens
– spend as much time in outdoor light as possible
– take frequent breaks throughout the day to look at the horizon and step out for a few seconds