You can barely get through the day without reading something about vitamin D; either it’s the latest miracle drug or its powers have just been debunked. Should you hustle out to the nearest big-box to buy a mega jar or just fuhgeddabout it?
Like many questions, the answer is complicated and the truth lies somewhere between the extremes. Vitamin D is definitely worth your attention, as it’s highly effective in promoting bone health, but its effectiveness in other areas is still only promising at best.
What’s Vitamin D? Taking vitamin D can reduce your risk of death, says the Archives of Internal Medicine, yet, according to the
New England Journal of Medicine, most people don’t get enough, thereby putting themselves at increased risk for disease if they’re D deficient.
You can get vitamin D in supplements and some foods. Called the “sunshine vitamin,” vitamin D is also synthesized in the skin with exposure to ultraviolet (UV) rays. Once taken or produced in your skin, your liver and kidneys convert vitamin D to a hormone that becomes a “gatekeeper” in your gut, helping your body absorb calcium and phosphorus. Most tissues and cells have receptors to take in vitamin D, which probably accounts for its effect on your body’s many systems.
What D does
Vitamin D forms and maintains bones by helping your body absorb and use calcium and phosphorus; it’s essential for strong skeletons. No matter how much calcium you take, if you’re vitamin D deficient, you’ll only absorb minimal amounts of it.
Vitamin D may also help prevent colorectal cancer deaths. A recent study in the Journal of the National Cancer Institute linked the protective benefits of vitamin D with decreased colon cancer deaths, but not deaths from other forms of cancer.
Increasing evidence also suggests that vitamin D helps maintain a healthy immune system. Several studies have noted an association between increased blood levels of vitamin D and decreased risk of autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis and type 1 diabetes.
Some researchers also suggested, in the Journal of Clinical Endocrin-ology and Metabolism, that very low levels of vitamin D could be related to pre-eclampsia in pregnancy—putting both moms and babies at risk.
What to take
If you’re a woman between ages 18 and 50, current recommendations call for 200 IU per day; that amount goes up to 400 IU daily between ages 51 and 70, and tops out at 600 IU each day for women ages 70 and older. Many experts argue that these recommendations are outdated and that research supports higher daily doses to achieve the best results. Currently, the Institute of Medicine (IOM) is revising its vitamin D recommendations, and it’s anticipated that higher doses will be advised, along with increased food fortification.
Check food and supplement labels to figure out how much vitamin D you’re getting. Many multivitamin supplements contain 400 IU; most calcium supplements contain vitamin D as well. For example, one Viactiv calcium soft chew contains 100 IU; Citracal caplets with vitamin D contain 400 IU per dose.
Only a few commonly consumed foods contain vitamin D naturally. In the U.S. we mostly depend on fortified milk—but not other dairy products—and breakfast cereals as food sources of vitamin D. Not all cereals are fortified with vitamin D, however.
If you’re lactose intolerant, try lactase products or vitamin D-fortified juices. Fatty fish such as tuna and salmon are also good sources. While rich in calcium, dark green leafy vegetables don’t supply vitamin D.
Although sunlight also stimulates vitamin D production, its effectiveness depends on adequate UV exposure. There’s no one good recommendation for sun exposure to get vitamin D—the rule of thumb is the darker your skin, the more exposure time needed to synthesize vitamin D. Also, the climate can affect exposure, so if it’s winter and you live in a northern industrial city and use a moisturizer with sunscreen, you probably aren’t getting enough sun to produce adequate amounts of vitamin D.
If you aren’t getting enough vitamin D from the sun or your food, try a supplement. Look for supplements containing vitamin D2 or D3. Getting Too Much? You can get too much vitamin D, but it’s extremely rare, and you typically can’t get too much vitamin D from the sun or from your food. But you can take in too much through supplements.
How much is too much? For many years the IOM has set the upper intake limit at 2,000 IU, while other experts want the upper limit raised to 10,000 IU. Until they can agree, what we do know is that there’s not enough evidence about long-term use of such high levels, especially in pre-menopausal women and infants, to warrant such a change.
Bottom line? You need vitamin D, so make sure you’re getting enough each day and ask your healthcare provider each time what the latest news is on this important vitamin.
