Vitamin D Facts

1
Vitamin D Facts

Picture of Sources of Vitamin D
Photo © Heather L. Brannon, MD

Vitamin D is an important chemical in the body that helps transport calcium from digested food in the stomach to the blood stream, so it can keep bones strong. There are two ways the body gets vitamin D:

  • Exposure to UV radiation
  • Ingesting foods or supplements that contain vitamin D

For years, some people have argued that it's better for your overall health to get vitamin D from

exposure to the sun

or a tanning bed, instead of

wearing sunscreen

and limiting sun exposure. You can find out more about this controversy and why it is not healthy to get

vitamin D from sun exposure or tanning

.

If you don't get your vitamin D from UV rays, though, how do you get it? Is it better to eat food with vitamin D or take supplements? How much vitamin D do you need and can you get too much? You can find the answers to these questions and more here:

2
How Much Vitamin D Do You Need?

Adapted from Michael Holick's "Vitamin D Deficiency" NEJM, 2007. Copyright © 2007 Massachusetts Medical Society. All rights reserved.

Most scientists and doctors agree that the dose of vitamin D recommended by the FDA is too low. These guidelines were established in 1997, and since then, good scientific studies have shown vitamin D taken in those doses doesn't prevent osteoporosis or broken bones.

How much is too much you ask? According to the FDA, 2000 IU is a safe dose for everyone, except children under 1 years old. Studies, however, have shown that adults taking doses up to 10,000 IU per day for five months did not have any evidence of vitamin D overdose.

Ultimately, the best dose for you needs to be determined with your doctor, but if you are a healthy adult and not pregnant or breastfeeding, you have the three options above.

There are two types of vitamin D:

  • Vitamin D2: Ergocalciferol, which comes from plants
  • Vitamin D3: Cholecalciferol, which comes from exposure to UV radiation and certain foods

Some studies have shown that D

3

raises vitamin D levels in the bloodstream higher than D

2

, but D

2

has been shown to be effective at preventing vitamin D deficiency at the right doses. The good news is you can use D

2

and D

3

to get all the benefits of healthy vitamin D levels in the bloodstream.

3
Foods With Vitamin D

Adapted from Michael Holick's "Vitamin D Deficiency" NEJM, 2007. Copyright © 2007 Massachusetts Medical Society. All rights reserved.

Vitamin D occurs naturally in some foods, such as salmon and Shiitake mushrooms. You can get vitamin D from exposure to sunlight, but to do this in a sensible way, you would need to consciously go outside and expose your arms and legs to 5 to 10 minutes of sunshine, then go back inside and apply your sunscreen for the day. Since most people would have trouble sticking with this routine, it may be better to have some salmon or tuna salad for lunch.

What if you don't like fish or you've had your fill of Shiitake mushrooms and egg yolks? Are there any other options? Of course there are. You could eat foods that have vitamin D added.

4
Foods Fortified with Vitamin D

Adapted from Michael Holick's "Vitamin D Deficiency" NEJM, 2007. Copyright © 2007 Massachusetts Medical Society. All rights reserved.

In the United States, milk and orange juice are fortified with vitamin D. Some yogurts and cheeses also have vitamin D added. Don't like or can't stomach dairy? You may want to get your vitamin D from fortified breakfast cereals.

What if you think you won't be able to get enough vitamin D from the foods you eat? Find out more about vitamin D supplements next.

5
Vitamin D Supplements

Adapted from Michael Holick's "Vitamin D Deficiency" NEJM, 2007. Copyright © 2007 Massachusetts Medical Society. All rights reserved.

Vitamin D supplements are probably the easiest way to get a good dose of vitamin D, and fortunately, you have several options. Infants and children need a prescription for the liquid supplements, but adults and children who can swallow pills have a lot of over-the-counter choices.

While it may sound like a good excuse not to slather up with sunscreen every day, getting your vitamin D from the sun needlessly exposes you to an increased risk of not only skin cancer but wrinkles and premature aging also.

6
Vitamin D Fact Sources

Sources:

American Academy of Dermatology. "Vitamin D Fact Sheet."

Gilchrest, BA. "The a-B-C-ds of sensible sun protection." Skin Therapy Letter. 13(2008): 1-5.

Gilchrest, BA. "Sun protection and Vitamin D: three dimensions of obfuscation." Journal of Steroid Biochemistry and Molecular Biology. 103(2007): 655-63.

Holick, MF. "Vitamin D deficiency." New England Journal of Medicine. 357(2007): 266-81.

Wolpowitz, D, and BA Gilchrest. "The vitamin D questions: how much do you need and how should you get it?" Journal of the American Academy of Dermatology. 54(2006): 301-17.

Continue Reading