Vitamin D has become a hot topic over the last few years. And that’s because science discovered what a big role it plays in our immune system. 

If you have the right amount of D, you’re better able to fight off infections - and you’re less likely to develop autoimmune diseases, heart disease and certain cancers. 

So here’s what you need to know about vitamin D. This comes from Dr. Michael Holick, the author of “The Vitamin D Solution." He says the reason we’re experiencing a worldwide vitamin D deficiency pandemic is because we don’t get out as much as we used to. For thousands of years, people got their required amount of vitamin D from the sun. But now most of us work indoors all day long.

The average adult needs a minimum of 600 international units of vitamin D a day. And Dr. Holick says you don’t need a blood test first to determine that you’re deficient. He says – we should all assume that we are! The only reasons you should consult with your doctor before taking a vitamin D supplement are: if you’re on anti-seizure medication, if you have a gastrointestinal problem, or a problem absorbing nutrients. 

So can’t we just get the D we need from the sun? 

Dr. Holick says the sun IS a good source in addition to taking a supplement. He says your best bet is to expose your arms and legs to the sun. They have a greater surface area and the skin isn’t as delicate as the skin on your face. So if you know you’ll burn without sunscreen in 15 minutes – only stay out for half that amount of time. But the darker your skin, the longer you’ll have to stay in the sun. So someone who’s Indian would need up to 4 times more exposure than someone with fair skin. 

And we should be eating vitamin D-rich foods too. Like a can of tuna – which has 200 IUs of vitamin D. Or canned salmon – which has 400 IUs. 

Vitamin D is fat-soluble – which means it gets stored in our body. But don’t worry about getting too much. The upper daily limit is 4-thousand international units – and you’d have to be a pill popping, salmon-eating, sun-worshipping maniac to get too much.