Over 75% of Americans are deficient in Vitamin D, an important vitamin for overall good health. In part one of this post we looked at forms of Vitamin D, it’s role in our bodies and how much we need to maintain strong bones and a healthy body. Now we’ll address some of the sources of Vitamin D, risk factors for deficiency, and Vitamin D testing.

Why Aren’t We Getting Enough Vitamin D?

There are basically three sources of vitamin D: food sources, sunlight and supplementation. It’s very difficult for most people to get enough Vitamin D through diet and sun exposure which requires most us to take a supplement. Here’s why:

Very few foods in nature contain significant amounts of vitamin D. The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources—about 400 IUs per serving. Small amounts (about 40-45 IUs) of vitamin D are found in beef liver, cheese, and egg yolks.

Fortified foods provide another source of the vitamin D in the American diet but not usually more than 100 IUs per serving. Almost all of the U.S. milk supply is voluntarily fortified with 100 IU of vitamin D per cup. Both the U.S. and Canada also require that infant formula be fortified with 40-100 IU/100kcal. (Other dairy products are not typically fortified with Vitamin D.)

So, unless you eat fatty fish every day and drink lots of milk or other fortified foods you’re not going to get enough from food sources.

As for Vitamin D from sunlight, getting 15–30 minutes of mid-day exposure to sunlight at least twice a week should be enough to maintain adequate levels of Vitamin D for most people. But, this too can be difficult as well. These days we spend more time indoors and use more sun protection than in times past.

We slather on sunscreen and use UV film on office building windows and car windows to shield us from the sun’s rays.

That leaves supplementation, which usually starts at about 400 IU of Vitamin D3 daily for adults and can increase to as much as 5,000 IU per day or more depending on the severity of deficiency. Larger doses are usually short term to increase serum levels quickly and then lowered to a daily maintenance dose once a healthy level is achieved.

Who Is at Risk for Vitamin Deficiency?

If you belong to any of the following groups, you may be at an even higher risk of vitamin D deficiency, in which case you may want to discuss vitamin D testing with your doctor. (More about Vitamin D testing below.)

• Infants who are only breast-fed or who get less than 2 cups each day of vitamin D fortified formula or milk
• People with dark skin (which doesn't absorb the sunlight as well as light skin). A new study from Northwestern University in Chicago found that African-American men living in areas with low sunlight are up to 3 ½ times more likely to have Vitamin D deficiency than Caucasian men and should take high levels of Vitamin D supplements.
• People who don't get a lot of exposure to sunlight
• People who use sunscreen often
• Older people are at very high risk, in part because aging skin doesn't absorb sunlight as well as younger skin
• People who are obese or have undergone gastric bypass surgery
• People who have medical conditions that interfere with their body's ability to absorb fat, such as cystic fibrosis, celiac disease, or pancreatitis
• People who have liver or kidney problems
• People who live in the northern hemisphere in the winter months
• People who take certain medicines, like anti-seizure drugs or steroids

Are you Getting Enough Vitamin D?

The best way to know if you are getting enough vitamin D is to have a specific blood test that measures your serum levels of Vitamin D produced by the skin or obtained from food and supplements. Otherwise, you may not know that you're not getting enough vitamin D until you start having symptoms associated with vitamin D deficiency.

According to the Institute of Medicine a person is at risk of vitamin D deficiency if their serum 25(OH)D concentrations are less than 30 nmol/L (<12 ng/mL). However, some people with impaired Vitamin D utilization are potentially at risk for low Vitamin D at levels ranging from 30–50 nmol/L (12–20 ng/mL).

Practically all people (97.5%) are sufficient at levels 50 nmol/L (≥20 ng/mL) or greater.

You can have too much of a good thing. Serum concentrations greater than 125 nmol/L (>50 ng/mL) are associated with potential adverse effects.

Sources:

Nutraingredients

National Institutes of Health