> be exposed to the sun: only reliable way to generate vitamin D in your body (helps bone mineralization)
I think sunlight exposure may be important for a healthy mental state as well. A few years ago I adopted a schedule of sleeping around 10AM and waking up around 6PM. I maintained a reasonable level of sun exposure in the morning, but I would usually wake up shortly after sunset leaving me without sun for the first half of my day. I found that after a few days of this I would wake up every day disappointed that I'd woken up in darkness again. Around this same time period I had no problems waking up at 3PM every day, even though I didn't always go outside while it was still light.
I think sunlight exposure may be important for a healthy mental state as well. A few years ago I adopted a schedule of sleeping around 10AM and waking up around 6PM. I maintained a reasonable level of sun exposure in the morning, but I would usually wake up shortly after sunset leaving me without sun for the first half of my day. I found that after a few days of this I would wake up every day disappointed that I'd woken up in darkness again. Around this same time period I had no problems waking up at 3PM every day, even though I didn't always go outside while it was still light.