[photochemsyn]

Or, install some full-spectrum daylight-mimicing LED lights. These are not that easy to find, you want to use the CCT and CRI ratings to match sunlight as closely as possible.

https://www.uvm.edu/news/extension/tips-choosing-grow-lights

They're kind of hard to find, the optimal values are 6500K for CCT and as close to 100 as possible for CRI, which matches the peak value and the overall spectrum of natural sunlight. One option appears to be the NorthLux™ 95 CRI T8 LED Tube (kind of pricy though, and will need a specialized ballast fixture, also a bit pricy).

[cyberax]

Vitamin D needs UV, not just light.

You _can_ install UV diodes, but then you have a whole another can of worms. A point source of UV can damage eyes much more easily, and if you forget to turn it off, you can expect a nasty sunburn.