Packing a Punch Vitamin D May Play a Role in Preventing Cancer, Heart Disease And Other Ailments
We've known for decades what vitamin D can do for your bones. Kids who don't get enough vitamin D get rickets. Adults who are deficient in D also can develop brittle, misshapen bones. In this job, vitamin D is cast in a supporting role; it's main function is ensuring calcium is absorbed into the bones and muscles.
But it turns out we might have been selling D short.
An avalanche of research over the past few years suggests vitamin D might play a role in preventing other diseases, independent of calcium:
- A Harvard study of more than 30,000 women published in May found premenopausal women with the highest vitamin D intake had 35 percent less breast cancer than those getting the least vitamin D.
- Another Harvard study in 2006 found white people with the highest levels of vitamin D had a 62 percent lower risk of developing multiple sclerosis.
- In a study published earlier this month, researchers in Nebraska found women who got 1,100 international units of vitamin D every day lowered their risk of any cancer by 77 percent. This study was small - just 1,179 women - but it was the most rigorous yet to examine vitamin D's impact on health.
Other studies point to a protective effect against cancers of the colon, prostate, ovaries, pancreas and kidney, as well as heart disease, Alzheimer's, diabetes, arthritis and other illnesses.
"The more we study this, the longer the list gets," said Cedric Garland, a prominent vitamin D researcher at the University of California-San Diego.
The clincher: Many of us aren't getting enough. Vitamin D researchers say the current recommendations for 200 to 600 international units a day are too low to protect against cancer and other diseases.
Most of us don't even get that much.
D is for deficient
Dr. Patrick Massey routinely tests vitamin D levels in his patients at Alexian Brothers Hospital Network in Elk Grove Village. Two years ago, he measured the vitamin D levels in blood samples of 80 healthy patients. Only three were in the normal range.
Patients who hail from north of the Mason-Dixon line (that includes all of Illinois) almost invariably end up low in D, Massey says. "We just don't get as much sun as we used to get, and we're not getting it in our diets," said Massey, who is medical director for alternative and complementary medicine at Alexian and a Daily Herald columnist.
The body synthesizes vitamin D from exposure to ultraviolet rays. Northerners get less sunlight, particularly in the winter, and studies have found we usually have less vitamin D in our blood. We've also become more cautious about the dangers of melanoma and other skin cancers from sun exposure. So sunbathing is out. Wider use of sunscreens has further limited UV absorption by our skin.
Vitamin D is present in fish and fortified dairy products, but otherwise is scarce in our diet. One cup of fortified milk has 98 international units of vitamin D, a quarter of the recommended intake for adults over age 51. According to the Institute of Medicine, half of American women are not consuming the minimum levels of vitamin D. The situation is worse for people with darker skin, who have a reduced ability to synthesize vitamin D from sunlight.
As a result, doctors report a re-emergence of rickets, particularly among black infants who are exclusively breast-fed. While breast-feeding conveys numerous health benefits to mother and child, mothers who are deficient in vitamin D will have lower levels in their breast milk.
The American Academy of Pediatrics recommends infants who are exclusively breast-fed should receive vitamin D supplements. Infant formula is fortified with vitamin D.
"We do know that people aren't getting enough vitamin D for bone health," said Victoria Rosenfeld, a licensed dietitian with DuPage Dieticians in Lisle.
A simple blood test can measure how much vitamin D is in your body. A nutritional assessment with a dietitian can also determine whether you're consuming enough vitamin D in your diet, Rosenfeld said.
Adding D
So how much do we need? And what's the best way to get it?
Federal guidelines recommend 200 to 600 units of vitamin D a day, depending on age. But most studies have found that higher doses are needed to protect against cancer and other illnesses.
Dr. Richard Hellman, an endocrinologist in Kansas City, Mo., and president of the American Association of Clinical Endocrinologists, recommends 1,000 to 2,000 units a day. Half of his diabetes patients are deficient, he said. "Vitamin D deficiency makes insulin resistance worse," Hellman said. "We're still trying to learn the exact way that's happening, but we do know it's happening." In the body, vitamin D acts more like a hormone than a vitamin. It signals the intestine to increase absorption of phosphorus and calcium, which helps build strong bones and aids in muscle and cardiac functioning. Researchers are learning vitamin D strengthens the immune system and helps regulate cell growth, a basic biologic process that goes haywire in cancer.
To get the amount that seems needed for cancer prevention, most people will need supplements, said Dr. Keith Block, medical director of the Block Center for Integrative Cancer Treatment in Evanston. Doctors haven't reached consensus on how much the average person should take. The Institute of Medicine has set the upper limit of recommended intake at 2,000 units a day for adults, but that's probably too cautious, Block said. "Evidence is increasing that this toxic limit has been set too low, and that much higher limits are actually safe," he wrote in an e-mail. Block leans toward 1,000 units a day for most adults. That's roughly the amount taken by women in the Nebraska study. Garland suggests adults take 2,000 units of vitamin D3 a day and spend five to 15 minutes a day in the sun with their skin exposed. "We always worry about putting people in the sun, but it's such a short time," Garland said. "Everyone should avoid the skin turning pink or red. For a very fair-skinned person, it may be only five minutes."
Such advice puts dermatologists on edge. "It confuses the public," said Dr. Darrel Rigel, president-elect of the American Society for Dermatologic Surgery.
The tanning industry has seized on such advice to market its products. But few doctors - even those who support modest sun exposure - recommend a visit to a tanning bed for an intense dose of UV rays. Statistically, one person dies every hour of skin cancer in the U.S., Rigel said. You can get vitamin D without intentionally exposing yourself to extra UV radiation.
"Studies have shown you get enough incidental exposure to the sun just walking to your car from the grocery store," Rigel said. "Or you can take vitamin D supplements, which cost less than a penny a piece."
Some populations are at particular risk of vitamin D deficiency. Supplements are recommended for elderly people, African-American and other dark-skinned people, babies who are exclusively breast- fed, people who do not get significant sun exposure, and those who live in northern latitudes.
If you do choose a supplement, doctors recommend one that uses vitamin D3, or cholecalciferol. Vitamin D2, or ergocalciferol, is less potent.
How much vitamin D do you need?
The Institute of Medicine has set a minimum amount of vitamin D to maintain bone health and normal calcium metabolism in healthy people:
- Birth to 50 years 200 units
- 51 to 70 years 400 units
- 71 years and older 600 units
- To protect against cancer and other diseases, studies have suggested adults get 1,000 to 2,000 units of vitamin D a day.
Source: National Institutes of Health Office of Dietary Supplements; Daily Herald interviews
Where to find vitamin D
In food:
Cod liver oil, 1 tablespoon 1,360 units
Salmon, cooked, 3.5 ounces 360 units
Tuna fish, canned in oil, 3 ounces 200 units
Milk, vitamin D fortified, 1 cup 98 units
Cereals, fortified, to 1 cup 40 units
Egg, 1 whole 20 units
Cheese, Swiss, 1 ounce 12 units
In sunlight:
The skin synthesizes vitamin D from ultraviolet rays. How much depends on geographical location and the intensity of the rays, as well as your skin type. Doctors urge caution; too much sun exposure increases your risk of skin cancer.
In supplements:
Look for vitamin D3, or cholecalciferol. Vitamin D2, or ergocalciferol, is less effective in preventing cancer.
Source: National Institutes of Health Office of Dietary Supplements; Daily Herald interviews
Chicago Daily Herald
06-27-07
sstevens@dailyherald.com
