Apr. 16, 2004
Knight Ridder Newspapers
Let's say you try to eat right. And take a multivitamin, chased by a glass of fortified milk.
But unless you're a sun-worshipper - and no one's suggesting you should be - odds are good that you're seriously lacking in vitamin D.
New research says that not getting enough vitamin D can hike your risk not only of bone fractures and osteoporosis, but also of several types of cancer and a range of autoimmune conditions, including rheumatoid arthritis and multiple sclerosis.
"Until recently, we defined vitamin D adequacy as not having rickets," said Robert Heaney, an osteoporosis researcher at Creighton University in Omaha, Neb. Rickets is a childhood bone-softening condition rarely found in this country. "We've suddenly become more alert to what's going on."
The emerging evidence about D's wide-ranging health effects has unleashed a heated debate. On one side are the vitamin D researchers who contend that the federal government has grossly understated how much vitamin D people need. Given the near-absence of food sources, they say many people probably need to spend more time in the sun. Sunlight causes the body to produce vitamin D.
On the other side is the dermatology community, which for years has campaigned against sunbathing and in favor of sunscreen. Many dermatologists fear that more sun exposure will only swell the nation's ballooning rate of skin cancer.
"I think it's wrong-headed, and there's going to be a problem down the road with tumors and sun damage," said Mark Naylor. He's a tumor biologist at the Oklahoma Medical Research Foundation in Oklahoma City. "I think most people get enough sun exposure to get sufficient vitamin D."
The Institute of Medicine's Food and Nutrition Board has set the daily adequate intake at 200 International Units (IUs) for people 1 through 50 years old, 400 IUs for people 50 to 70 years old and 600 for people older than 70.
Those recommendations are "totally arbitrary" and far too low, given recent findings about vitamin D, said Bruce Hollis. He's a nutritional biochemist at the Medical University of South Carolina in Charleston who has built his career on vitamin D. "I assure you that during the next cycle of the Food and Nutrition Board in 2007, there will be dramatic changes."
At least 150 years ago, a teaspoon of cod liver oil was given to children to prevent and treat rickets. Early in the 20th century, scientists discovered that it was the vitamin D in that foul-tasting elixir that fortified bones. Because a teaspoon happened to contain about 400 IUs of vitamin D, the federal panel adopted it as the standard, Hollis said.
"If they'd used haddock liver oil, which has 700 IUs of vitamin D, that would have been the standard." Hollis and others say there are indications that many Americans aren't getting enough vitamin D. A couple of pediatric clinics in North Carolina found that during the 1990s, rickets increased threefold - and more than fourfold among African-American babies.
Several clinical studies show that elderly people given 800 IUs a day had fewer fractures, lower blood pressure, better balance and better muscle tone than people given a placebo, according to Reinhold Vieth, a biochemist at the University of Toronto.
The connection between vitamin D and cancer is more circumstantial, but intriguing. Cancers of the breast, prostate and large bowel occur more commonly as one moves away from the equator. The theory is that people have less sun exposure. Clothing is one factor. The other is that in some places, the sun is too weak to trigger vitamin D synthesis from November through February.
Scientists have found that prostate cancer cells don't have uncontrolled growth when treated with vitamin D, Vieth said. And there's a good reason for that. Vitamin D acts like a control switch, telling cells how they are to function.
Skin cells, which constantly replace themselves, normally spread out in a smooth, flat sheet.
"What keeps them from cauliflowering out?" Heaney asked. "Turns out it's vitamin D. Colon, breast and prostate cancer may be lying at the feet of vitamin D insufficiency." That's not to say that if you're short on vitamin D, you will develop one of those cancers.
"Lots of things have to go 'right' for cancer," Heaney said. "But a low level of vitamin D could mean that you've lost one of your lines of defense."
Researchers also have looked for a relationship between vitamin D and autoimmune disorders, particularly multiple sclerosis and rheumatoid arthritis. Autoimmune disorders happen when the body's immune system turns against an organ or a system of the body, rather than on a foreign invader like a virus. Vitamin D is known to depress the body's immune system.
It's well-established that MS rarely occurs in people living near the equator and becomes increasingly common in people at higher latitudes with less sunshine. MS also tends to occur less frequently at higher altitudes, where the sun shines more potently.
A recently published study found that women getting at least 400 IUs of vitamin D daily from food and supplements were 40 percent less likely than others to develop MS. A team tracking rheumatoid arthritis and vitamin D intake among a group of older women found that women who got less than 200 IUs a day were 33 percent more likely to develop rheumatoid arthritis than women who consumed more.
All of which raises the question: How much vitamin D is enough?
The Women's Health Initiative, a large clinical test of the role of hormone therapy and other factors in women's health, expects to add information to the picture next year. A group of women has been receiving 1,000 milligrams of calcium and 400 IUs of vitamin D daily. They're being monitored for bone fractures and colon cancer.
Some insist there's enough evidence now to hike the dose endorsed by the federal government. Heaney takes 1,000 IUs a day. Hollis recommends 2,000 units "without any hesitation."
Darker-skinned people need even more, especially during the winter and if they live in the northern United States. Skin pigment acts like sunscreen, limiting the body's ability to make vitamin D.
"I think the majority of African-Americans are deficient," said Hollis. "I think the typical African-American probably needs at least 2,000 to 4,000 units a day."
The difficulty here is that vitamin D naturally occurs in only one food: fish. And you'd have to eat several servings daily to get even 1,000 IUs.
Supplements are an option, but most multivitamins have modest amounts. Higher-dose vitamin D supplements are hard to find, although some Web sites sell them. Just don't overdo it.
The other way to hike your vitamin D is to let the sun do it. That horrifies dermatologists like Mark Naylor, the tumor biologist.
"Melanoma is going to be the most prevalent cancer in the U.S. in 15 years, which should scare everyone," he said. Although he doesn't necessarily think that 30 or 40 minutes of midday sun each week would cause cancer, Naylor worries that people tend to take moderate recommendations and run with them.
And yet Naylor concedes that the theories about vitamin D deficiency and cancer and autoimmune conditions are plausible. The sorts of research considered most credible - controlled clinical studies - haven't been done. And other than the Women's Health Initiative, they probably won't be, researchers pointed out, because there's not enough potential for profit in vitamin D to motivate a company to pay for the research.
So in view of the new, tantalizing theories, Naylor said, he recommends engaging in "normal activities" outdoors, but certainly not sunbathing. And to patients concerned about vitamin D, he recommends dietary supplements and fortified foods.
If it's true that more vitamin D would help to ward off some cancers and autoimmune conditions, Naylor said, "We should do it in a safe way and not make melanoma the No. 1 cancer in the nation."
HOW TO GET VITAMIN D
MAIN SOURCE: THE SUN
The time it takes to stimulate skin to produce vitamin D depends on skin tone and the sun's intensity (determined by time of day, elevation and time of year). Here, the sun isn't strong enough from about November through February. Most African-Americans' can't meet their vitamin D needs from the sun at any time of year.
From April to October, the typical white person can make adequate vitamin D by:
Each week, spending 30 or 40 minutes in the sun between 10 a.m. and 2 p.m., wearing a swimsuit or the equivalent but no sunscreen.
Increasing the time if you're wearing more clothes.
Because vitamin D is stored in body fat, it remains available for a couple of months. During winter, a supplement might be advisable.
Source: Bruce Hollis and Robert Heaney, vitamin D researchers
The federal government recommends 200-600 international units of vitamin D a day. Some researchers recommend at least 1,000. Besides supplements, try:
Copyright © 2004, Knight Ridder Newspapers