Vitamin D: The Powerhouse That Makes Everything Work Better

Think of Vitamin D as the workhorse of the vitamin world, something that has the potential to make every cell in your body function better. Its superpowers include helping to produce hormones, strengthen bones, protect the heart and support the immune system by fighting off bacteria and viruses. Yet nearly 40 percent of Americans are deficient — double that for black- and brown-skinned folks.

How Can I Get More Vitamin D?

In a perfect world, all of our vitamin D would come from diet and exposure to sunlight. In reality, not everyone can make time or feels comfortable spending 15 minutes in direct sun with about half of their skin exposed two to three times a week. (Hello, skin cancer.)

Can’t I Just Use Sunscreen?

Yes and no. Our skin requires ultraviolet light to transform vitamin D so that we can absorb it. If you apply sunscreen, the effect of those UV rays is decreased. Depending on the time of day, one way to have your vitamin D and protection too is to wait 15 minutes after you hit the pool, beach or ball field before you apply sunscreen.

What About Diet?

Not many foods naturally contain vitamin D. It is present in milk; in fatty fish like salmon, tuna and mackerel; and in small amounts in beef liver, egg yolks and cheese. For this reason, many foods in the U.S. are fortified with vitamin D — meaning the vitamin has been added — including milk, cereal, orange juice and other juices.

Know Your Levels

Perhaps the most important thing to do before you consider taking vitamin D supplements is to have your current level checked via a blood test. This is often done as part of your annual physical and lab work — if it’s not, ask for vitamin D to be measured during your next test. Blood levels below 10 nanograms per milliliter indicate severe deficiency; between 20 and 30 indicates a risk of deficiency; 30 or up is good. (There is such a thing as too much vitamin D — more on that in a moment.)

How much vitamin D an individual needs can vary a lot. In the first year of life, an infant can get all necessary vitamin D through breast feeding. From years 1 to 4, a child needs about 600 international units a day, equivalent to three cups of milk or one cup of fortified juice or cereal. (Vitamin D is measured in both micrograms [mcg] and international units [IU]; 1 mcg of vitamin D is equal to 40 IU.) For women over 40, more is needed to prevent osteoporosis, which is often treated with calcium that has vitamin D added. Think of vitamin D as calcium’s best friend — without it, we’re not able to absorb the calcium as well, so it’s less available to our bodies. Taken together they help to prevent weak, fragile bones.

Who Needs Supplements?

Anyone whose blood work shows low levels of vitamin D is a candidate for supplements — your doctor or dietitian can suggest how much to take and how often. But there are other reasons a person might need supplementation.

Vitamin D is fat-soluble, which means it needs some fat in order to pass easily through a cell membrane. But for those with autoimmune or inflammatory issues, or whose intestines are damaged, absorbing vitamin D through diet can be a problem.

For black- and brown-skinned people, often of Hispanic descent, it’s more difficult to get enough vitamin D via sunlight because of their skin type, so they can need supplementation. People who live in far northern latitudes, where there’s less sunlight for much of the year, also often need supplements.

Gender can have an effect, too: Teenage girls tend to need a bit more because their bones are developing and they are entering puberty and menstruation. Breastfeeding women can need more because they are sharing their body’s nutrient supply with their infant.

Is Too Much Vitamin D Dangerous?

Taking supplements without knowing what your vitamin D level is, or taking supplements too frequently or in unusually large doses, can lead to vitamin D toxicity. If your blood measurement gets up in the 150 ng/ml range, you can experience nausea, vomiting, confusion, muscle and bone pain, dehydration or even loss of appetite.

Does Vitamin D Help Fight Disease?

Many studies have shown that vitamin D promotes bone health and prevents osteoporosis or controls its progression. It also can help with heart disease by lowering cholesterol and helping to control blood pressure. Studies also show that having proper vitamin D levels can help alleviate depression; it’s also been shown to improve inflammatory bowel disease and ulcerative colitis. New research shows benefit for use against diabetes and cancer, but those studies are not yet conclusive.

The Bottom Line

Knowing your vitamin D level is an important part of a healthy lifestyle, along with exercise and a balanced diet. African American and Hispanic folks need to have their levels checked more often, along with people who live in areas that experience little sunlight in winter.