How can I get enough vitamin D?

David Slovik, MD
Endocrinology Diabetes & Metabolism
Vitamin D is made in the skin after exposure to sunlight. Some people make all the vitamin D they need by going outside for a few minutes a day without sunscreen. You should keep your exposure time short -- just 10 to 15 minutes a day -- to protect against skin cancer. However, it's likely that sunlight alone won't generate adequate amounts of vitamin D. For example, if you live above 40 degrees latitude (the latitude of Denver, Indianapolis, and Philadelphia), the winter sunlight isn't strong enough to enable you to produce significant amounts of vitamin D. Sunscreen, glass, and clothing also interfere with this process, diminishing your ability to produce the vitamin. And as you age, your skin can't produce vitamin D as readily, and your intestines have more difficulty absorbing this vitamin.
You can try to make up for the shortage with your diet, but only a few foods -- such as eggs, saltwater fish, and liver -- contain vitamin D. In the United States, milk is fortified with this vitamin; an 8-ounce glass should have about 100 IU. Taking one daily multivitamin is an easy way to get vitamin D. However, since most multivitamins contain 400 IU, although some now have higher amounts of vitamin D, you may need to supplement this with another source, such as a vitamin D capsule or a teaspoon of cod-liver oil. It's not wise to simply double up on your multivitamins, since that will deliver unhealthy amounts of other nutrients, such as vitamin A, which can lower bone density.
Don't overdo it with vitamin D, though. Keep your daily intake below 4,000 IU a day. In general, you'll get far less than that from food, sunlight, and a multivitamin, but if you're taking several different vitamin pills, it's important to review your daily dose.
Spending just 20 minutes a day in the sunshine -- without sunscreen -- during the summer months provides enough vitamin D to last you through the year, says Dana Simpler, MD, a physician in private practice in Baltimore. "People with dark complexions may need up to an hour," she says. You can also get vitamin D from supplements and foods such as dark leafy greens, and vitamin D-fortified orange juice and soy milk. According to the Institute of Medicine, most people need 600 IUs of vitamin D a day. People ages 71 and over require 800 IUs of vitamin D daily, possibly more, depending on their health.
Dr. Michael Roizen, MD
Internal Medicine
Even in summer, few North Americans get enough sun to activate their skin's vitamin D3 factory for long (why it's called the “sunshine vitamin”). In winter, vitamin D deficiencies are way worse. The sun's rays are too wimpy to have much effect. Yet D3 (vitamin D's most active form) is essential. It protects you from brittle bones, hypertension, heart attacks, strokes, diabetes, certain cancers and more. It even perks up your memory.

Here are some tactics for getting more vitamin D3:
  • Start with food. Canned salmon is terrific: 500 IU of D in 3 ounces. Canned tuna's good, too: 200 IU in 3 ounces. Each glass of D-enriched OJ and nonfat milk adds another 100 IU.
  • Take a supplement. Swallow 1,000 IUs of D3 a day, 1,200 after 60. Taking it with your omega-3s boosts absorption. (Taking it with a meal helps too.)
  • Get a blood test for D3. It's the only way to know how you're doing. If it's low (below 50), adjust and recheck in three months. Your payoff: Adults with the highest D3 have the fewest "cardiometabolic disorders," a cluster of nasties that includes heart disease, diabetes and metabolic syndrome.

Doctors and scientists agree that sun protection is essential to prevent skin cancer and to reduce its toll on human health. Strict sun protection has been shown to exacerbate vitamin D deficiency.

But exposure to ultraviolet B (UVB) rays, whether from the sun or from artificial tanning, is also the most important environmental risk factor for skin cancer. The American Academy of Dermatology has stated that “there is no scientifically validated, safe threshold level of UV exposure from the sun that allows for maximal vitamin D synthesis without increasing skin cancer risk.” The Academy recommends increased intake of foods naturally rich in vitamin D, vitamin D-fortified foods and vitamin D supplements.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.