Vitamin D deficiency is rampant. Are we overdoing it with the sunscreen?
Vitamin D deficiency is rampant. Are we overdoing it with the sunscreen?
Nutrition Diva is hosted by Monica Reinagel. A transcript is available at Simplecast.
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Annie, from my hometown of Buffalo, NY, wrote with questions about vitamin D:
"My doctor, my mom, and various magazines have touted the benefits of Vitamin D for bone health, cancer prevention, mood boosting (especially in winter), weight loss, and cold/flu prevention. Is this just hype or is there some truth this?"
You’re right, Annie. Vitamin D is very hot right now. Up until recently, vitamin D’s big claim to fame was that it prevented rickets, a serious bone deformity that can affect kids and babies. Because vitamin D is not widespread in the food supply, health authorities in the U.S. decided back in 1932 that all milk should be fortified with vitamin D in order to prevent rickets. And that’s pretty much the last anyone thought about it.
But we may have underestimated the importance of this vitamin. Over the last few years, researchers have noticed two things. One, people who have heart disease, diabetes, depression, various auto-immune diseases, osteoporosis, several types of cancer, and even obesity also seem to be low in vitamin D.
The second big news flash is that lots of us are deficient in the vitamin. Just last month, a new report found that seven out of ten American children, for example, are low in vitamin D. Vitamin D deficiency is also a particular concern in the elderly and those with dark skin, and everyone is at greater risk during the winter months.
As I said, vitamin D is not very common in foods. About the only foods that naturally contain a meaningful amount of D are oily fish like salmon and mackerel--and the dreaded cod liver oil. Many of us don’t eat fish that often and even fewer take cod liver oil. And now, we (and our kids) also drink less milk than we used to. So fortified milk isn’t picking up the slack it used to.
Seeing that vitamin D is an essential vitamin, isn’t it strange that it isn’t found in more foods? I mean, you can trundle on down to any grocery store in land-locked Kansas and pick up some fish for dinner. But what did people do in the days before we had such well-traveled food? What did everyone who didn’t live near the sea and know someone who fished do to get vitamin D? Seems like a pretty serious design flaw.
But here’s the thing that makes vitamin D a little different than any other nutrient I can think of: Food wasn’t really meant to be our primary source of this nutrient. Sunlight was. Human skin has a pretty nifty trick: it produces this vitamin when it is exposed to UV rays. No matter how far you live from the ocean, there’s going to be at least some sunlight.
The sun gets weaker the further you go from the equator, of course. And that’s why humans who originated from the northern and southern region of the globe have lighter skin than those who originated from closer to the equator.
Lighter skin allows more UV through, which ensures that people living further from the equator, where the sun’s rays are weaker, can make enough vitamin D to stay healthy. Dark skin acts as a sort of natural sunscreen, providing some protection against the stronger UV rays at the equator, but still allowing for sufficient vitamin D production.
Pretty clever system, huh? But consider our current situation. First, we wear clothes. Second, we work and play inside. Third, lots of dark-skinned people now live far north or south of the equator where the UV rays are weak. Not surprisingly, dark-skinned people living in the U.S. are six times more likely to be deficient than light-skinned folks. And finally, light-skinned people are told never to step outdoors without slathering themselves in sunblock, which prevents wrinkles and skin cancer but also blocks vitamin D production.
The end result? Rampant vitamin D deficiency. And now that low vitamin D levels are being linked to an ever-growing list of illnesses, researchers are wondering whether getting more vitamin D into people could make everyone a lot healthier. Many experts are arguing that the current recommended daily allowance for vitamin D is way too low and needs to be doubled or even tripled. And vitamin D supplements are flying off the shelves.
It’s all very exciting but you have to realize that scientists are still unraveling the connections between vitamin D and disease. A lot of what I’ve read in the media puts the cart ahead of the horse.
For example, we don’t know exactly how vitamin D might protect against heart disease. In fact, we don’t even know for sure whether it protects against heart disease. It could be that it’s the other way around: heart disease might create vitamin D deficiency. Or it could be that something that contributes to heart disease also coincidentally depletes vitamin D and that increasing vitamin D wouldn’t do anything to improve the heart disease.
Vitamin D clearly plays an important role in immune function—both the part that regulates auto-immunity as well as the part that protects you from infectious disease. But I haven’t seen any research confirming that taking vitamin D supplements will increase your resistance to cold and flu.
And, although overweight people are more likely to be deficient in vitamin D, I’m afraid I can’t find any research showing that increasing vitamin D intake will enhance weight loss. Sorry.
Rest assured that research is steaming along, full speed ahead. And, while vitamin D may not turn out to be the cure for all that ails us, all this press has been a good reminder that we need to pay attention to be sure that we’re getting enough of it.
The current recommended intake for vitamin D for adults is 200 to 400 IU. If you’re over 70, it goes up to 600 IU. I think there’s a fairly good chance that these recommendations will be raised within the next couple of years. The American Academy of Pediatrics has already increased its recommendation for children and adolescents from 200 to 400 IU.
What does it take to get the recommended amount? A glass of milk has about 100 IU. A small serving of salmon has about 400IU. Most multi-vitamins provide 200 to 400 IU and many calcium formulations now include vitamin D, as well.
You can also meet your vitamin D needs by exposing your skin to the sun—without sunscreen. You may have read that 10 to 15 minutes of sun per day will do the job. But it’s a little more complicated than that. It all depends on where you are, how high you are, how much skin is exposed, how dark your skin is, the time of day, and the time of year.
I found a great little calculator developed by Norwegian scientists that can help you determine how much sun you need to meet your daily vitamin D requirement, taking all those factors into consideration. It’s very interesting to play around with. For example, I learned that here in Baltimore, in August, I’d need just 5 minutes of sun at midday to top off my vitamin D stores. If I were back home in Buffalo with Annie, I’d need an extra minute or so. If it were November in Buffalo, I’d need about 40 minutes. If it were November in Buffalo and I were black, I’d need two and a half hours.
I’ll put a link to the calculator in the show notes, with a disclaimer. It’s not a very user-friendly interface. In fact, I found it extremely confusing at first. So I’ll also include a link to a blog post that explains in detail how to get accurate results.
Whether you’re getting your D from food, supplements, or sunshine, the recommended amounts are based on how much you need to maintain adequate vitamin D levels in your body.
For some reason, although it only takes a few hundred IU of vitamin D to maintain blood levels, it can take an enormous amount of supplemental vitamin D to restore them. If you’re deficient, you might need to take 10,000 to 50,000 IU a day for a few weeks to get your levels back up to normal.
Although vitamin D supplements are pretty safe, these kinds of megadoses could potentially cause problems. If you’re concerned or curious about your vitamin D status, ask your doctor to order a blood test. If it comes back low, he or she can advise you on what to do next.
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Have a great day and eat something good for me!