Life as a medical writer is not for those with an active imagination. With each new disease that comes under your editorial microscope, you begin to examine yourself for signs. A bad night’s sleep? Apnea, no doubt. That hint of a fever last week? H1N1 for sure. Throw in a whiff of creativity, and you can easily convince yourself that you’re suffering from asthma or Alzheimer’s or Asperger’s syndrome — and that’s just the A’s. So when a colleague recently had his vitamin D levels tested and scored a paltry 14 (it should be at least 30 and preferably 40 to 50), I began to wonder — what was my own level?
Vitamin D deficiencies — both mild and severe — are rampant in this country. A national sample of nearly 19,000 individuals found that between 1988 and 2004, the proportion of Americans with adequate levels of vitamin D in their blood fell from 45 percent to 23 percent. Among blacks, those with sufficient levels plummeted from 12 percent to just 3 percent.
And that could spell trouble for a large portion of the U.S. population. Traditionally, scientists have thought of vitamin D as necessary mainly for bone health, because it helps the body absorb calcium. But recent research shows that vitamin D performs a multitude of other functions. And though much work remains to be done, one thing is clear: Vitamin D does far more than doctors realized even a decade ago.
“We should test for vitamin D as routinely as cholesterol,” says Dr. Daniel Nadeau, medical director of the Diabetes, Endocrine, and Nutrition Center at Exeter Hospital in
New Hampshire. Dr. Nadeau tests about 70 percent of his patients — and finds that almost all have suboptimal levels.
Deficiencies are being linked to some of the most serious chronic diseases. In 1997, epidemiologists Frank and Cedric Garland found that people with blood levels below 30 had three times the risk of colon cancer. Last year the famous Framingham heart study linked levels below 15 with a 60 percent greater likelihood of a heart attack.
Other studies have drawn tentative links between low D and elevated risks for multiple sclerosis, rheumatoid arthritis, asthma, and depression. In fact, if you drew a chart of the human body with arrows pointing to each organ affected by vitamin D, it would start to resemble a painting of Saint Sebastian, the martyr who met his end in a hail of arrows.
Beyond Bone Health
Researchers who gave people 800 to 2,000 units of vitamin D a day have found that those who received the supplements had lower risks for a variety of ailments — 80 percent lower for type 1 diabetes, 72 percent lower for falls in nursing homes, and 60 percent lower for multiple cancers. More studies are needed, but the results so far point pretty consistently in the same direction. “Vitamin D is not a magic pill, but it’s as close as you’ll ever get,” says Dr. John Cannell, president of the Vitamin D Council.
How can one substance affect so much? Dr. Michael Holick, professor of medicine, physiology, and biophysics at Boston University Medical Center and author of The Vitamin D Solution, slated for release next spring, offers an explanation.
“Virtually every tissue in the body has vitamin D receptors,” he says. “They have to be there for a reason.”
And that reason seems to be that vitamin D helps regulate genes throughout the body — genes that help control blood pressure, cell proliferation, and inflammation, among other things. They even rev up the immune system — not the antibodies that target specific germs, but the general-purpose cells that attack any foreign invader. For this reason, Dr. Cannell speculates that vitamin D could be a huge help in battling viral infections, including the H1N1 (swine) flu. “You should still get the vaccine,” he says. “But I wouldn’t dream of letting my family face H1N1 this winter with blood levels under 50.” In principle, few problems are easier to fix than vitamin D deficiency.
|5 Foods For Vitamin D||Vitamin D (IUs)|
|Salmon, cooked (3.5 ounces)||360|
|Atlantic mackerel, cooked (3.5 ounces)||345|
|Sardines, canned in oil (1.75 ounces)||250|
|Tuna, canned in oil (3 ounces)||200|
|Vitamin D-fortified milk (1 cup)||98|
|Source: National Institutes of Health|
There are three sources of vitamin D — sunshine, supplements, and foods.
Foods naturally high in vitamin D include fish, such as salmon, mackerel, sardines, and tuna. Milk, breakfast cereals, and some brands of orange juice are fortified with vitamin D. Those rays of golden sun — specifically UV-B radiation — stimulate the synthesis of the vitamin in the skin. That distinguishes it from other vitamins, which can only be obtained through food or pills. Dr. Holick recommends venturing into the sun with bare arms and legs daily without sunblock, but only for five to 10 minutes.
“Moderation is the word,” he says.
That leaves daily supplements. Currently, the recommended level of supplemental vitamin D is 200 international units (IUs) for individuals 19-50; 400 IUs for those 51-70; and 600 IUs for 71-plus. The Institute of Medicine, however, is expected to issue revised recommendations in 2010.
Some researchers are already taking more.
At a meeting at the Centers for Disease Control and Prevention this year, Dr. Robert Heaney of Creighton University passed out slips of paper to the other vitamin D researchers and asked them to jot down how much they take. He takes 3,000 units a day. “The average among my peers was more than 5,000,” he says. That sounds breathtakingly high compared to the current guidelines, but it’s not. “People with high sun exposures get 15,000 to 20,000 IUs a day from the sun with no sign of vitamin D toxicity,” says Dr. Edward Giovannucci, professor of nutrition and epidemiology at Harvard School of Public Health.
That said, there will never be a one-size-fits-all recommendation for vitamin D intake. There are too many variables. The obese need more than the thin because of their larger body size. The elderly need more than the young because they are less efficient at synthesizing it. Those who live at northern latitudes need more than those near the equator, where sunshine is more abundant year-round. Even individuals have different requirements at different times of the year.
As for me, I finally got the results of my vitamin D test: My level was 34 — just barely acceptable, but at least in the ballpark. “Increase your supplementation and get tested again in six months,” my doctor advised. Mind you, I was already taking 1,200 IUs a day and probably getting a couple hundred more from food. And despite wearing sunblock, sun-protective clothing, and floppy hats, my supersensitive skin is probably still synthesizing vitamin D during my
45-minute daily walks.
Even though I had an acceptable level, Dr. Nadeau said it may be “because you got tested in the summer.” Come winter, he hinted, I might slip into inadequate territory — but nothing I couldn’t fix with a few more supplements.