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What you need to know about vitamin D

Jan 23, 2018
By Ellen Dinerman
Rocky mountain with sun peeking through

Confused about whether or not you’re getting enough vitamin D? You’re not alone.

Vitamin D research is hot these days. Vitamin D deficiency has been associated with everything from depression to multiple sclerosis and poor bone health. Because of that, many people take vitamin D supplements to make sure they getting enough, especially in the winter. Still, association does not mean causation — it’s not actually clear whether supplements are helpful. In fact, recent studies seem to bring up more questions than answers.  

We took a look at the evidence to get down to the bottom of it. Here’s what you need to know about vitamin D.

What is vitamin D?

Vitamin D is actually not a vitamin but a hormone, and your body often gets it through food or supplements. Vitamin D supports bone growth and regulates calcium, phosphate, and parathyroid hormone levels. One of the things that makes vitamin D unique, though, is that it’s also produced by your skin cells when sunlight hits your exposed skin — one of the reasons why people often worry about deficiencies in winter more than summer.

What does vitamin D deficiency cause?

Vitamin D deficiency is most strongly associated with weak bones. Extreme vitamin D deficiency causes soft bones and skeletal deformities in children (more commonly known as rickets), and can cause weak bones in adults (known as osteomalacia). Osteoporosis (low bone mass and structurally weak bones) is related to low levels of calcium and vitamin D.

Though not as well established, low vitamin D levels have also been associated with immune function and falls and frailty in the elderly, as well as chronic diseases including colon cancer, heart disease, and diabetes (remember, though, that association does not equal causation!).

Some groups of people are at higher risk of vitamin D deficiency.

  • Older adults. Adult skin does not produce vitamin D as efficiently, and older adults often spend more time indoors, limiting their sun exposure.
  • Exclusively breastfed infants. Human milk does not contain adequate amount of vitamin D.
  • People with darker skin. The increased amount of melanin pigment reduces the skin’s ability to produce vitamin D.
  • People with certain gastrointestinal conditions or gastric bypass. Gastrointestinal conditions or gastric bypass procedures can reduce your ability to absorb the vitamin.  
  • People taking certain medications. If you’re taking steroids, some weight loss drugs, or some anti-seizure medications, they can affect Vitamin D levels.

How can I increase my vitamin D intake naturally?

The two easiest ways to naturally increase your vitamin D levels are by eating certain foods and through sun exposure.

The best sources of vitamin D are fatty fish like salmon, tuna, and mackerel. Other foods with lesser amounts include beef liver, cheese, egg yolks, and some mushrooms. In the United States, vitamin D is also added to most milk, many cereals, yogurt, margarine, and orange juice.

If you’d prefer to get your vitamin D through sun exposure, it’s important to be make sure you’re balancing getting the right amount of vitamin D and staying healthy in the sun. Fortunately, it doesn’t take a lot of time to get adequate exposure — just 5 to 30 minutes between 10 a.m. and 3 p.m. can be enough. UVB radiation from tanning beds can also stimulate your skin’s production of vitamin D. If you choose to go this route, though, remember that exposing your skin to direct sunlight and UVB radiation from tanning beds also puts you at increased risk of developing skin cancers.

A number of factors can also impede your skin’s ability to make vitamin D. This includes sunscreen (any SPF greater than 8) and cloud cover. Glass windows also filter out the wavelength of light that produces vitamin D.

Should I get my vitamin D levels checked?

Generally, there’s little evidence to support getting vitamin D levels checked if you’re an otherwise healthy person.

So, what can you do? Talk to your doctor about taking vitamin D supplements if you’re concerned that you’re not getting enough. For adults older than 65, there is some evidence that vitamin D may reduce the risk for falls, but a recent study suggested that vitamin D supplements do not protect against bone fractures.

What’s the bottom line?

While we know vitamin D is an important hormone with a variety of functions, current evidence questions whether supplementing vitamin D for healthy people actually helps. For those individuals who require vitamin D therapy, we suggest 600 to 800 international units (IU) daily of vitamin D3. If you’re taking other multivitamins, double check the total amount of vitamin D you’re consuming since it is possible to take too much.

Finally, no matter what group you fall into, the best way to support healthy bones is through a healthy lifestyle and diet that includes natural sources of calcium and vitamin D along with weight bearing exercises, avoiding too much alcohol, and not smoking. And if you need help getting started with those changes, give us a call or schedule an appointment. Our primary care providers are here to help you get started with healthy lifestyle changes.

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Ellen Dinerman

The One Medical blog is published by One Medical, a national, modern primary care practice pairing 24/7 virtual care services with inviting and convenient in-person care at over 100 locations across the U.S. One Medical is on a mission to transform health care for all through a human-centered, technology-powered approach to caring for people at every stage of life.

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