If you’re chained to an office chair most of the day, there’s a good chance you’re not seeing much sunlight—which means you’re likely missing out on your daily dose of vitamin D. And that’s not a good thing.

Lower vitamin D levels could mean your bones aren’t able to absorb calcium as well. Plus, vitamin D is also necessary for cell growth and immune function. So, in other words: It’s pretty damn essential.

Your recommended daily allowance of vitamin D is 600IU (or 15 micrograms), so get some sun and supplement with food. Pickings are somewhat slim, but these sources make it more accessible than you think—plus most are packed with protein, too. Score.