Stupid d vitamin amounts over long time leads to a buildup of calcium in the blood which causes a bunch of problems. From wikipedia:

The recommended dietary allowance is 15 μg/d (600 IU per day; 800 IU for those over 70 years). Overdose has been observed at 1,925 μg/d (77,000 IU per day).[citation needed] Acute overdose requires between 15,000 μg/d (600,000 IU per day) and 42,000 μg/d (1,680,000 IU per day) over a period of several days to months. Source

XC skate skiing when there’s snow, running with spiked shoes when there’s not. Dark when going to/from work usually, so getting out in the weekends is important. Walk/run in the middle of the workday is great, but something that I don’t do nearly enough.

D vitamins. I also have a daylight lamp at work, but haven’t started using it yet.