Five Myths and Facts About Vitamin D

All About Science

What’s known to be true about vitamin D has changed a lot in recent years. An impressive body of research over the past couple of decades has shed new light on the roles vitamin D plays in human health and wellness. Here are some common misconceptions and important facts to know about a vital nutrient that virtually every cell in your body needs.

MYTH: You can get enough vitamin D from food.

This is simply not true, unfortunately. Only a few foods contain vitamin D, and those only contain very small amounts, making it all but impossible to get enough vitamin D from food alone. Dietary sources of vitamin D include oily/fatty fish (salmon, tuna, herring, sardines, and mackerel), egg yolks, beef liver, mushrooms, and foods fortified with vitamin D, such as milk, orange juice, cereals, and infant formula. Even these foods generally contain only small amounts of vitamin D3—less than 150 IU per serving. To get enough vitamin D, you need to consistently expose your bare skin to sunlight, or take vitamin D3 supplements.

MYTH: If you live where it’s sunny, you’re probably getting enough vitamin D.

Our bodies make vitamin D when we expose our bare skin to sunlight. But how much vitamin D we can make depends on a multitude of factors: time of day, seasonal time of year, your geographic location, altitude and cloud cover (or smog), your skin’s pigmentation, your age, and whether or not you wear sunscreen. Even if you do live in a sunny place, it’s possible, and even likely, that you’re still not absorbing enough vitamin D from the sun for optimal health.

During the winter months, the UVB portion of the sun’s rays is low-to-nonexistent in northern latitudes—not enough to produce vitamin D. The further north you live from the equator, the less UVB there is available. North of Atlanta, there isn’t enough UVB to produce vitamin D from about November to February; north of New York City, the same is true from about October through March.

How can you know if there’s enough UVB available from sunlight for your body to make vitamin D? There’s an easy and fun way. Just check the length of your shadow, recommends the Vitamin D Council. If your shadow is longer than you are tall, then you aren’t able to make enough vitamin D (due to the oblique angle of the sun), and you should consider boosting your vitamin D supply with a daily D3 supplement. There are also smartphone apps you can download that calculate how much vitamin D you’re able to get in your location.

FACT: Vitamin D is actually a hormone, not a vitamin.

One of the things that makes vitamin D unique compared to other vitamins is that it’s not a vitamin at all! Often termed “activated vitamin D” or calcitriol, vitamin D behaves like a hormone in our bodies, carrying out essential biological functions through endocrine, paracrine, and intracrine mechanisms. This helps explain why and how vitamin D regulates so many more physiological functions than previously thought. Vitamin D receptors have been found in nearly every tissue and cell in the body. In recent decades, this has led to an impressive and growing body of research into vitamin D’s previously unknown roles in optimizing a wide range of bodily processes.

FACT: Vitamin D does more than just help build strong bones.

Vitamin D has long been known for its role in bone health, helping to regulate the way our bodies absorb calcium and phosphorus.* But the more recent discovery that nearly all tissues in the human body are responsive to vitamin D has led to new areas of research investigating other roles that this vital nutrient plays—many more roles than were known even just a couple of decades ago. These promising areas of research include vitamin D’s roles in muscular strength, cardiovascular health, cellular health, longevity, immune health and function, and immune-related health issues.* One recent review of existing studies found that vitamin D has been explored in relation to 137 different health outcomes, spanning a broad range of bodily systems. This new generation of research suggests that vitamin D is much more than a “bone health” nutrient, and that sufficient vitamin D is required for achieving optimal human health overall.*

FACT: The FDA recently doubled the percent daily values for vitamin D.

The blood test that measures your vitamin D status is called a 25(OH)D serum test. In light of more recent vitamin D research, there is a growing consensus that the optimal range for 25(OH)D levels is above 75–80 nmol/L for most people.

Even as we learn more about vitamin D’s roles in nearly all aspects of health, however, data suggests that most of us don’t get enough vitamin D. National Health and Nutrition Examination Survey (NHANES) data shows that the number of persons with levels below 75 nmol/L nearly doubled from 1994 to 2004. Almost 80% of the 2004 survey population had levels below 75 nmol/L, while close to 75% had levels below 50 nmol/L.

Recommended Daily Intakes for Vitamin D

Sources: Vitamin D CouncilFDA 2016 RulingEndocrine Society
To help people get more vitamin D, health organizations continue to raise their recommended intakes. Back in 2010, the U.S. Food and Drug Administration (FDA) doubled the daily values for vitamin D, which are based largely (but not exclusively) on daily reference intakes from the Institute of Medicine of the National Academies. In 2016 the FDA doubled the daily values for vitamin D again—from 400 IU (10 mcg) to 800 IU (20 mcg) for adults and children over 4.

While these updates are a big improvement, many researchers and experts arguethat the current recommendations for vitamin D intake may still be low given that vitamin D deficiency is widespread across all age groups, regions, and seasons. This is why it’s important to test your vitamin D levels to get an accurate, personal assessment, even if you don’t think you’re deficient.

Adding a quality vitamin D3 supplement to your daily routine is a simple way to help ensure you’re getting enough of this all-important nutrient, rain or shine.

* These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

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