Shanna R. Levine, MD
Instructor of General Internal Medicine
The Mount Sinai Hospital
A Quick Guide to Getting Enough Vitamin D
If you are like many of my patients, you may be wondering, "Am I getting enough vitamin D?" This is a valid concern, because vitamin D plays a very important role in overall health and, in fact, many people do not get enough. The Centers for Disease Control and Prevention estimates that about one-third of Americans have insufficient levels. The good news is that sources of this vitamin are easily accessible.
Why Is Vitamin D Important?
Vitamin D helps the body absorb calcium from the gut, as well as maintain normal blood levels of calcium and phosphate. These minerals are essential for healthy, strong bones. Bones are constantly being built up and broken down, like a building continuously under construction to maintain its integrity; in medicine we call it "remodeling." Vitamin D supports both the growth and maintenance of the bone. This essential vitamin also aids the regulation of cells throughout the body, and helps our nerves, muscles, and immune system function properly. New research is finding that it is also involved in reducing inflammation.
When You Don't Get Enough
A lack of vitamin D can weaken bones, leading to rickets in children and osteoporosis in adults. This is why elderly people, who tend to have lower vitamin D levels, often require supplements to prevent brittle or thinning bones. Symptoms of a deficiency may include generalized fatigue, muscle weakness, bone pain, or a foggy feeling.
How Much Do You Need?
Vitamin D is measured in international units (IU). The National Institutes of Health recommends that most people get 600 IU of vitamin D per day, or, if you are over 70 years old, 800 IU. A vitamin D blood test is the best way to establish your baseline level and see whether you are getting enough. It is especially important for those at increased risk of deficiency to get their vitamin D checked. This includes people with dark skin; those who get little sun exposure; elderly people; vegetarians; people with gastrointestinal disease or who have had gastric bypass surgery; and those on certain anti-seizure medications, like phenobarbital and phenytoin.
Sources of Vitamin D
Sources of vitamin D are limited to a few natural foods, some fortified foods, dietary supplements, and sun exposure:
Sun Exposure. The body makes its own vitamin D when the skin is exposed to ultraviolet B (UVB) rays from the sun. It is hard to give clear recommendations for sufficient sun exposure, as many factors play into UVB absorption, including skin tone, age, geographical location, time of day, environmental factors like fog and smog, and sunscreen application.
That said, try to get 10 to 15 minutes of exposure at least once or twice a week, depending on skin tone, with fair skin requiring less time in the sun. Sunscreen--a vital tool in skin cancer prevention--does block UVB rays. However, since its application is usually imperfect, people can absorb adequate sunlight even while wearing sunscreen.
Fortunately, your body stores vitamin D in liver and fat cells. If you get enough sunlight during the summer, your body can stockpile some of the vitamin D it makes to use later in the year when you may not get enough either through the sun or diet.
Natural Foods. It is always best to get vitamin D from natural sources when you can. Significant amounts are found in fleshy fish like salmon, swordfish, and tuna, as well as some types of mushrooms. For most people, canned tuna or cod liver oil are easy fixes. Eggs, liver, beef, and sardines also contain vitamin D, but at lower levels. You may find it helpful to keep a one-day food diary to see if you are ingesting an adequate amount through a natural diet.
Fortified Foods. To make up for the lack of natural sources, in the United States some foods are fortified with vitamin D, notably milk and orange juice. Many cereals are fortified, too. The United States Department of Agriculture website provides a database of nutritional content, where you can find the best sources of vitamin D for both natural and fortified foods.
Dietary Supplements. For people who need extra vitamin D, the lowest supplementation typically recommended is 1,000 IU orally per day. For highly deficient patients, we will give a 50,000 IU pill once a week. It is almost impossible to take toxic levels of vitamin D.
Work With Your Physician
I encourage patients to have a working relationship with their primary care physician and get an annual checkup to monitor their overall health. If you are not feeling well and suspect that your vitamin D level is a cause, it is best to see your doctor to determine if supplementation is necessary. The right tools and support from a knowledgeable and empathetic primary care doctor are an important key to a healthy, active life.