Opt for stand-alone vitamin D supplements to reduce the risk of contamination.

Interest in vitamin D is on the rise.

RODALE NEWS, EMMAUS, PA—While consumers should always beware of supplements plagued by contamination with harmful ingredients, stand-alone supplements of vitamin D—a substance believed to help protect against cancer, dementia, and heart disease, among other ailments—get high marks in third-party quality-assurance tests, according to a new report by a consumer-watchdog group.

Just as good, the vitamin can be dirt-cheap if you know what to look for. "The quality is generally high with vitamin D, and it's relatively an inexpensive ingredient," explains Tod Cooperman, MD, president of ConsumerLab.com, an independent company that evaluates health-and-nutrition products. "It's good news all the way around, not like some new, superexpensive vitamin. You shouldn't have to pay very much to get a vitamin D supplement."

THE DETAILS: A recent ConsumerLab.com survey, conducted annually to gauge what dietary supplements people are using, found that vitamin D use jumped 30 percent since last year. The D surge is undoubtedly a result of dozens of studies linking low vitamin D levels to health problems. Nearly half of the 6,000 people surveyed took vitamin D daily.

Dr. Cooperman's lab also tested 27 different brands of vitamin D supplements last year, randomly purchased from pharmacies, natural health stores, and vitamin stores. In addition, ConsumerLab.com tested supplements at manufacturers' requests, for certification purposes. Researchers checked that vitamin D, vitamin D plus calcium, and vitamin D plus vitamin K products weren't contaminated with harmful substances like lead; that they contained the amount of vitamin D they advertised; and that they broke down accordingly, allowing proper absorption. ConsumerLab.com charges to see the complete report, but Dr. Cooperman shared some of the results with Rodale.com.

WHAT IT MEANS: As scores of studies are finding health problems associated with vitamin D deficiency, more consumers are flooding store aisles to get their hands on the vitamin. That's because it's not readily available from food sources in meaningful amounts, other than in wild-caught salmon, mackerel, and some shiitake mushrooms. But the interest in vitamin D is leading some supplement makers to add vitamin D to all sorts of other herbal and supplemental concoctions, which opens the door for contamination.

Here's how to get your hands on the best vitamin D supplements without breaking the bank:

• First off, get enough. Most people in the United States aren't getting enough vitamin D, a substance our bodies naturally manufacture when sun hits our unprotected skin during warmer months. But because so many people are wearing sunscreen to protect against skin cancer, they're not getting the benefit, since the product blocks the beneficial process as it blocks the sun. And in northern latitudes, the angle of the sun isn't sufficient to spur such production, for much of the year anyway. Vitamin D expert Michael Holick, PhD, MD, professor of medicine, physiology, and biophysics at Boston University School of Medicine and author of the upcoming book The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problem (Hudson Street Press, April 2010), suggests that all children receive at least 400 International Units (IU) and up to 1,000 IU of vitamin D a day (the American Academy of Pediatrics recommends 400 IU); for adults, Dr. Holick suggests 1,500 to 2,000 IU a day. That's well above the current official recommendations of 400 IU for adults, but most doctors agree that that amount is woefully low and doesn't bring patients' blood levels of vitamin D up to adequate levels. Before taking vitamin D supplements, ask your doctor for a routine blood test to see where you stand, and then supplement accordingly. And during the warmer months, consider letting the sun hit your unscreened arms and legs for 15 minutes or so, to spur some natural D production.

Read on for more quality vitamin D brands that won't break the bank.