The Sunshine Vitamin

D is an essential nutrient our bodies D-mand. But are you getting too little — or too much?

You may know that vitamin D helps strengthen bones and teeth, but do you realize it’s also important for cognitive function and may improve muscle form and function too? This vitamin is equally essential for men and women: A low vitamin D level can cause fatigue or exhaustion, mood problems, reduced immune function and weaker bones. Vitamin D also helps your immune system fight off bacteria and viruses.

There are two ways to get vitamin D, also known as “the sunshine vitamin”: through food and through direct exposure to sunlight, which helps your body to create this nutrient. “We need sunlight to convert the inactive forms of vitamin D2 and vitamin D3 to the active form, 25 hydroxy vitamin D,” says Diane Schwartz, M.D., who practices internal medicine at Old Tappan Medical Group in River Vale, part of the Englewood Health Physician Network. And because vitamin D is only available in select foods, Dr. Schwartz says, it may be difficult to eat enough to get the recommended quantity. (D-rich foods include salmon, tuna, sardines, herring, eggs—especially yolks—liver and cod liver oil.)

Your primary care provider should test your vitamin D level annually during your routine blood test. If it’s low, he or she will suggest supplementation options. Meanwhile, try these tactics to make sure to get this essential vitamin:

• Eat a variety of foods that provide vitamin D. Besides the aforementioned foods, milk and yogurt are often fortified with vitamin D as well.
• Consider taking a vitamin D supplement. The recommended amount for adults is to take a minimum of 1000 IU (international units) and up to 4000 IU per day of vitamin D3, the inactive form that converts most easily to the active form, says Dr. Schwartz. However, keep in mind that too much vitamin D can be harmful. Very high levels can cause calcium buildup, weakness, nausea and vomiting and an excessive need to urinate. Consult with your physician about possible interactions with any supplement if you’re also taking a prescription medication.
• Get outside. Many people whose work is indoors or who live in latitudes far from the equator don’t have sufficient exposure to the sun to create enough vitamin D. (Luckily, the latter isn’t an issue for those of us in New Jersey.) But now the days are getting longer and warmer, so take advantage! Remember that your body doesn’t make vitamin D from sunlight through a window—only when your bare skin is exposed to the sun. Sunscreen also limits the amount of vitamin D your skin produces. (But use sunscreen, of course, to guard against skin cancer.)

WHO’S AT INCREASED RISK?

According to the National Institutes of Health’s Office of Dietary Supplements, some people are more likely to have trouble getting enough vitamin D, including:

Breastfed infants: Breast milk alone does not provide infants with enough vitamin D. Older adults: With age, the skin’s ability to make vitamin D when exposed to sunlight declines.

People with dark skin: The more melanin in one’s skin, says Dr. Schwartz, the less vitamin D one absorbs from sunlight exposure.

People with conditions that limit fat absorption: Examples include Crohn’s disease, celiac disease and ulcerative colitis. This is because the vitamin D consumed is absorbed in the gut along with fat; if the body has trouble absorbing fat, it will also have trouble absorbing vitamin D.

People who are obese or have undergone gastric bypass surgery: These folks may need more vitamin D than others.