Why You Need Vitamin D
Turns out, calcium needs a little help. Vitamin D is a fat-soluble vitamin that helps your intestines absorb calcium, and indirectly helps keep calcium in your bones. Without vitamin D, calcium can get accumulated in places it doesn’t belong or bypass absorption entirely. Basically, you need vitamin D to make calcium work for you. Plus, recent research suggests that D’s benefits go beyond bones, supporting cellular function and overall wellbeing.
How You Get It
While you can get vitamin D from food, most reliable sources are animal-based: oily fish, eggs, and milk. It’s harder for people with plant-based diets to get enough from food alone. The good news is that your body can actually make vitamin D itself from endogenous synthesis in the skin. It works like this: your skin absorbs UVB photons from the sun. When these photons pair with a substance called 7-dehydrocholesterol that’s naturally in your skin, vitamin D3 is created.
Why You Might Be Deficient
Despite the fact that we can make vitamin D ourselves, many of us are still low. You know how you sit in an office all day? That doesn’t help. And neither does the fact that most of us wear sunscreen when we get sun exposure. Since UVB radiation has been shown to cause major skin damage, sunscreen is the right choice. It just makes it harder to get your vitamin D.
Those of us with darker skin also have a harder time making vitamin D ourselves. Melanin in darker skin actually absorbs UVB photons, competing with 7-dehydrocholesterol and preventing it from pumping out vitamin D.
If you live in the far north (anywhere above Boston or Portland), you’re out of luck come winter.
UVB cannot penetrate the atmosphere between October and April in locations where the latitude is greater than 42 degrees north, so your vitamin D skin synthesis is insignificant during the chilly months.
How to Tell If You’re Low
Feeling tired, grumpy, or kind of sad? Sweaty even when it’s not that hot? These may be signs of low vitamin D levels. In 2011, The Endocrine Society, based on numerous research studies, recommended that adults get at least 1,500 to 2,000 IU of vitamin D every day. Our scientists are on board with this recommendation and included 2,000 IU in Essential for Women. So keep putting on sunscreen and stay huddled under a blanket all winter: we’ve got your vitamin D covered.