Vitamin D deficiency

Dear Alice,

I recently had lab work done that identified a vitamin D deficiency. My level was eight and my doctor says that 30 is considered a normal level. I was then prescribed a vitamin D2 pill to help bring my levels up. I just read something that said vitamin D3 is the preferred type to use as a supplement and that 30 isn’t considered the “normal” level anymore, that the number should be closer to 40 or 50.

A few questions: Is it better to use D3 or D2? What level is considered normal? What are the effects of vitamin D deficiency?

Dear Reader,

Ahh, good old vitamin D is one of the most versatile and vital vitamins. The 25-hydroxy vitamin D test is currently the most accurate way to measure a person’s vitamin D level. Maintaining vitamin D levels of at least 30 nanograms per milliliter (ng/mL) is recommended and levels over 125 ng/mL have shown to negatively impact health, such as increased rates of cancer. Conversely, vitamin D levels above 350 ng/mL are considered toxic, although that seems to occur very rarely. Levels below 20 ng/mL are considered inadequate for bone health as low levels of vitamin D can lead to increases in parathyroid hormones. This can cause bones to deteriorate in order to maintain calcium levels throughout the body. Speaking with your health care provider may help you better understand your test results. Extremely low levels of vitamin D can cause bones to become thin, brittle, or misshapen. Vitamin D deficiency is also associated with an elevated risk of cancers of the colon, breast, and prostate; high blood pressure and cardiovascular disease; osteoarthritis; and immune-system abnormalities.

So what about this vitamin is vital? When combined with calcium, vitamin D promotes calcium absorption, helps maintain bone health, and is crucial for bone growth and remodeling. Adequate levels of vitamin D can prevent rickets in children and help protect adults from osteoporosis. In addition, adequate levels of vitamin D can prevent osteomalacia, where bones soften due to lack of mineralization (which is a process that requires sufficient levels of vitamin D). Vitamin D is also key for regulation of cell growth, neuromuscular and immune function, and reduction of inflammation. Many genes that regulate cell growth, differentiation, and cell life cycle are also regulated in part by vitamin D.

The methods of getting enough of this vitamin is also particularly versatile. Aside from vitamin D supplements, most people obtain the recommended amount through exposure to ultraviolet B (UVB) rays in sunlight. Researchers have found that exposure to the sun without sunscreen (except on your face, of course!) between 5 and 30 minutes per day, at least twice per week, can lead to sufficient vitamin D production. However, it’s good to keep in mind that too much UV exposure can increase your risk of skin cancer. If you’ve already got your vitamin D time covered, you may consider covering up your body with adequate clothing and sunscreen.

Those who can’t get enough sun exposure may consider the use of a vitamin D supplement. It appears that at standard doses, D2 and D3 supplements are equally effective. At high doses though, D3 may be more effective than D2. Speaking with your health care provider again can help you decide which supplement is best for you. The current recommended daily intake of vitamin D, as established by the Institute of Medicine, is as follows:

  • 400 International Units (IU) for infants under 12 months
  • 600 IU for individuals between the ages of 1 and 70 (including people who are pregnant or lactating)
  • 800 IU for adults older than 70 years old

Unfortunately, very few foods in nature contain vitamin D. Most vitamin D in the American diet comes from fortified foods such as cereal or milk. For example, cow’s milk and plant-based milks can be fortified with vitamin D in the United States. Fatty fish and fish liver oils (especially cod liver oil) are also good natural sources. Small amounts of vitamin D may also be found in beef liver, cheese, egg yolks, and some types of mushrooms.

Something else to consider is that medications may impair the body’s ability to absorb and metabolize vitamin D. For example, corticosteroids (such as prednisone) can reduce calcium absorption and impair vitamin D metabolism. Both phenobarbital and phenytoin, used in preventing and controlling epileptic seizures, increase the metabolism of vitamin D to inactive compounds and reduce calcium absorption. Additionally, the cholesterol drug cholestyramine as well as some weight loss drugs can reduce the absorption of vitamin D and other fat-soluble vitamins. It’s wise to make sure your health care provider knows if you’re taking any other medications, so you can work with them to create a plan for vitamin D intake that works for you.

Here’s to happy bodies and healthy vitamin D levels!

Last updated Jul 24, 2020
Originally published Mar 06, 2014

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