The Vitamin You're Probably Deficient in Without Realizing It

Most Americans don't have to contend with serious vitamin deficiencies, thankfully, but with an increasingly sedentary, indoor-dwelling population, fewer and fewer people get enough vitamin D. While it may not cause totally debilitating effects for everyone, a vitamin D deficiency can have some pretty serious consequences. 

Why you need vitamin D

For kids, lack of what's known as the "sunshine vitamin" may result in rickets, which can bring along a whole bunch of fun stuff like bone deformities and fractures. While rickets in children is now rare in America, deficiency in vitamin D can cause a ton of issues even in adults, ranging from inflammation, a crappy immune system, osteoporosis, autoimmune disease, type 2 diabetes, as well as less-serious but still annoying symptoms like severe fatigue, hair loss, and an overall feelings of garbage-ness.

The Food and Nutrition Board (FNB) at the Institute of Medicine of The National Academies says that basically everyone who isn't a baby should take in at least 600 international units (IUs) -- unless you're over 70, then bump that up to 800 IUs. But no matter who you are, there's a good chance you're not getting enough.

nicoise salad with tuna and egg vitamin d

It's way harder to find vitamin D than you'd think

For something that every human needs to function well, vitamin D is an elusive substance. There really aren't a lot of naturally occurring sources of D in our foods -- a major source for vitamin D is our skin and the sun, which work together to magically create vitamin D our bodies can use. This probably worked out OK in the old days when our ancestors didn't wear much clothing and were outdoors nearly all day, every day. But that's not the reality most people experience today.

The best natural food sources may not be the most appealing, but here they are: cod liver oil, fatty fish such as salmon and tuna, and other fish liver oil. You can also find smaller amounts in some mushrooms, eggs (eat the yolk!), and beef liver. Most milk in the US is fortified with vitamin D, as are some orange juices and breakfast cereals, as well as some other dairy products like cheese and yogurt (read the labels to make sure).

woman relaxing on the beach and sunbathing and reading

Those UVB rays aren't ALL bad

In recent decades, health experts have warned that exposure to the ultraviolet B rays in sunshine can kill us by way of skin cancer, and as a result, more and more people have taken heed and avoid the sun completely, or load up on sunscreen when they're outside. This is a good idea if you don't want skin cancer (which nobody does), but it also means your body doesn't get to do the cool thing it was designed to do, which is convert those UVB rays into vitamin D.

The general consensus is that some sun exposure is OK (experts say about half the time it takes your skin to turn pink and begin to burn is a goal you should shoot for), but supplementation is probably necessary to obtain optimal levels, especially if you're at high risk for skin cancer.

How do I know if this is something I should worry about?

A lot of factors play a role here, including your race, your habits, and your age. In other words, if your skin is dark, you lurk indoors, you shun the sun, you're a vampire, or you're growing older (as we all are), then your vitamin D levels may not be where they should be. Since only about 30% of people fall within adequate ranges, it's more likely than not that you could stand a bit more.

There really is no general consensus on optimal levels (obtained through a blood test), which makes diagnosing a true deficiency challenging. The Vitamin D Council says that anything under 30 ng/ml should be considered deficient, but the National Endocrine Society says anything under 20 ng/ml is cause for concern, although those who test between 20 and 30 ng/ml might want to consider supplementation.

Bottom line? If you feel like garbage, have your doctor run a blood test to see where you fall. If your doctor suggests supplementation, do it -- and don't worry, even the 5,000-IU pills are tiny.

Sign up here for our daily Thrillist email, and get your fix of the best in food/drink/fun.

Monica Beyer is a health writer who is vitamin D deficient and knows more about it than she ever thought possible. Follow her: @monicabeyer.