Why You Need More Vitamin D

From the Editors of Live Right Live Well

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“I drink a lot of milk, so I’m probably fine.” So says Boston resident Doug Bennett in response to all the recent attention given to vitamin D. But like most Americans with the same ho-hum reaction, he’s oh-so-wrong. Why? Milk and other foods don’t contain nearly enough vitamin D to meet most people’s needs, and while your body actually makes its own vitamin D from sunlight, people are spending more and more time indoors -- and when we do go out, we slather on sunscreen, which protects against skin cancer but also prevents vitamin D production. And now that we’re heading into winter ... well, you can see where this is heading.

Americans Don’t Get Enough Vitamin D
An alarming three out of four Americans are seriously short of vitamin D, according to the results of a recent study conducted at the University of Colorado. And while 77 percent of Caucasians are in jeopardy, nearly all African-Americans (97 percent) and most Hispanics (90 percent) need more D. (This is because their darker skin prevents them from making as much D from sunlight as people with lighter skin.) Moreover, a new study published in the September issue of Pediatrics reports that 70 percent of children don’t get enough D.

While today’s vitamin D shortfalls are less dramatic than the severe, rickets-producing deficiencies of the past, it’s far more insidious. Researchers have found that insufficient vitamin D has serious, far-reaching ramifications, including:

• Higher rates of cancer Some of the strongest research links low D levels with colon cancer, which is much more common at northern latitudes. In fact, the active form of vitamin D inhibits cell growth, making it a natural cancer fighter. “All cancers, even melanoma [skin cancer], have a strong link to low D levels,” notes Robert P. Heaney, M.D., of the Osteoporosis Research Center at Creighton University in Omaha, Neb.
• Increased risk of heart disease and diabetes Among children in the Pediatrics study, those with insufficient D had higher blood pressure and lower levels of high-density lipoprotein (HDL) cholesterol (the good kind), both of which put them at risk for future heart disease. Adolescents in the study also had elevated blood sugar, foretelling a flirtation with diabetes.
• More colds and flu In the University of Colorado study, “low vitamin D levels were associated with a 35 percent increased risk of respiratory infections, like the common cold and influenza,” says lead researcher Adit Ginde, M.D. “For those with chronic lung conditions, the link was even stronger -- people with asthma had five times the risk of respiratory infection, those with emphysema twice the risk.”
• A host of other maladies As research continues, experts are finding that insufficient vitamin D levels are tied to a host of maladies, including pregnancy-related complications, Parkinson’s disease, multiple sclerosis, arthritis and even dementia.

How Much Vitamin D Do You Need?
While the recommended dietary allowance (RDA) is still 400 international units (IU) of vitamin D per day, nearly every expert will tell you that’s simply not enough, and you can bet the RDA will change next year when a government panel weighs in. “Most Americans need at least 1,000 IU a day,” says Ginde, “and many require even higher doses.”

What about the milk that Doug Bennett touts as his saving grace? When the government mandated vitamin D fortification to prevent rickets, they set the level at 100 IU per cup. That was fine when we were aiming for 400 IU a day, but it won’t get you close to the 1,000+ IU experts recommend today. Moreover, few foods contain vitamin D naturally. There’s a little in fatty fish and egg yolks, but not enough to make a big difference. And from November to February, even the sun can’t do its thing. It just isn’t strong enough. So to make sure you get enough of this essential nutrient:

• Take a vitamin D supplement. Michael Holick, M.D., Ph.D., director of the Vitamin D Laboratory at Boston University, recommends 1,000 to 2,000 IU daily, especially in the fall, winter and spring. And don’t worry about getting too much; one study found that 10,000 IU a day is safe, even when taken for a year.
• When buying supplements, be sure to look for D3 (cholecalciferol), which is much better absorbed than D2 (ergocalciferol).
• Try to get 10 to 15 minutes of unprotected sun on your arms, neck and face every day. (The risk of harmful effects is small as long as you don’t overdo.)
• Ask your doctor to check the 25-hydroxy vitamin D levels in your blood. For the most accurate results, get tested in the winter, when your D level is at its lowest. Aim for at least 30 ng/mL.

Vitamin D is the new “it” nutrient for a reason. Research shows it does so much more than we thought, at a time when we’re getting far less than we ever did. So enjoy your milk, take a D3 supplement, get some sun and have your D blood level checked. Your body will thank you.

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Susan Male-Smith is a registered dietitian and freelance nutrition and health writer. She has written for Family Circle, Redbook, Child and American Health, and is a former editor of the Environmental Nutrition newsletter and co-author of Foods for Better Health, among other titles.