How Vitamin D Deficiency Affects the Body

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Of the 13 essential vitamins, vitamin D might be one of the most unique.

It's one of the few vitamins your body can produce itself. Well, almost by itself. It needs a little help from the sun — hence why it's often referred to as the "sunshine" vitamin. You can also get vitamin D through your diet.

But when you aren't making or getting enough of it, you might feel the effects of low vitamin D.

"Vitamin D deficiency has become increasingly common over the last decade or so. And this is concerning since a deficiency in vitamin D can have lasting effects on a person's health and wellness," says Dr. Donald Brown, primary care practitioner at Houston Methodist.

Left untreated, vitamin D deficiency can lead to osteoporosis in adults, rickets in children and adverse outcomes in pregnant women. It may also be linked to heart disease, diabetes and cancer — although more study is needed on the topic.

And while a little bit of sunshine may sound like the simple answer to making sure you're getting enough vitamin D every day, be warned. It's a bit more complicated than that.

What are the symptoms of vitamin D deficiency?
Vitamin D plays several important roles in your body, including helping to:

  • Maintain strong bones and teeth
  • Promote proper muscle function
  • Facilitate communication between your brain and body
  • Fight off infection

"Given these important responsibilities, it's no wonder that being deficient in vitamin D can lead to health consequences," adds Dr. Brown.

However, he also points out that the immediate the signs aren't always noticeable in adults, until the deficiency is severe.

Symptoms of vitamin D deficiency can include:

  • Fatigue
  • Muscle weakness and/or pain
  • Joint pain
  • Depression

"If you're noticing these signs, talk to you doctor. He or she can use a blood test to evaluate your vitamin D levels and advise whether you're deficient and may need to supplement your intake," recommends Dr. Brown. "In fact, regardless of whether you're experiencing these symptoms or not, your doctor will check your vitamin D levels at your annual physical."

Why does vitamin D deficiency occur?
There are several reasons for an adult to have reduced vitamin D levels, including:

  • Increasing age – the skin's ability to produce vitamin D declines over time
  • Reduced exposure to the sun – your body only produces vitamin D when your skin is exposed to sunlight
  • Having darker skin – skin tone affects the amount of vitamin D produced when in the sun, with fair-colored skin producing it easier than darker skin
  • Lack of vitamin D in the diet – although very few foods naturally contain vitamin D, many are fortified with it
  • Health conditions that affect how well your body absorbs or processes vitamin D, including Chron's disease, celiac disease, ulcerative colitis, cystic fibrosis, obesity and chronic kidney or liver disease
  • Some medications and medical procedures, such as laxatives, steroids, drugs taken to treat high cholesterol, seizures or tuberculosis, as well as gastric bypass surgery

"It's important to address low vitamin D levels, but doing so requires working with your doctor to develop an effective, safe treatment plan. While reduced exposure to the sun can be a source of lower vitamin D levels, increasing sun exposure is not recommended as a source of vitamin D since this can increase your lifetime risk of developing skin cancer," warns Dr. Brown.

Additionally, he points out that overdoing it and taking in too much vitamin D can also be harmful to your health.

Are vitamin D deficiency symptoms reversible?
The good news is that vitamin D deficiency is treatable — under the guidance of your doctor, that is.

"The goal is to restore your vitamin D levels back to normal and maintain them there," says Dr. Brown. "What it takes to do this varies from person to person, and your doctor will use your lab results to offer a plan that will work best for you."

One way to elevate your levels is to eat foods rich in vitamin D, including:

  • Trout, salmon, tuna and mackerel
  • Foods fortified with vitamin D, including milk and some types of orange juice and yogurt
  • Mushrooms, cheese and egg yolk, although these foods contain small amounts

In some cases, your doctor may recommend taking a vitamin D supplement. What's the best vitamin D supplement to take? Well, that varies.

"Vitamin D is included in most multivitamins but there are also supplements that contain only (or primarily) vitamin D. There are two types of vitamin D found in supplements, D2 and D3. Vitamin D3 supplements can be found over-the-counter, while vitamin D2 supplements require a prescription. Your doctor will help you understand which is right for you," says Dr. Brown.

Most importantly, Dr. Brown reiterates the importance of talking to your doctor before taking a vitamin D supplement, or any supplement for that matter.

"You can absolutely overdo it with vitamin D, with the side effects ranging from nausea, constipation and increased thirst and urination, to confusion and the slurring of your words," warns Dr. Brown. "And while you can't get too much vitamin D from the sun, do not attempt to increase your sun exposure as a way of self-managing vitamin D deficiency, as this can increase your risk of developing skin cancer."