Recommendations for increasing intake of the nutrient are under consideration and sometimes trigger controversy
April 5, 2004
Susan J. Landers
Here comes the sun! And, in limited amounts, some say it could be all right -- at least in terms of an important nutrient it could help deliver to the body.
Physicians who favor some sun exposure aren't interested in tans. They are paying heed to findings that vitamin D, which is found in some foods but is made in abundance by our bodies after exposure to sunlight, can prevent many diseases.
These findings also could spur a change in the preventive messages about never going outside without sunscreen, especially for patients who rarely see the light of day, live in northern climes or have dark skins.
But such thinking also triggers controversy and even disdain from other
physicians who have worked hard to communicate to patients that sun exposure
is a dangerous link to skin cancer. They fear that linking sunlight to
vitamin D's purported benefits will undermine these other communications.
Vitamin D promise
Research is pointing to vitamin D as a possible cancer preventive, a boon to heart health and a potential player in preventing a host of autoimmune diseases, including type 1 diabetes, multiple sclerosis and arthritis. Deficiencies also were recently pegged as a possible culprit among people with persistent and nonspecific bone and muscle pain and the reason that more elderly women experience falls.
Thus, physicians such as Michael Holick, MD, PhD, a professor of medicine, physiology and biophysics at Boston University School of Medicine, advocate limited sun exposure. "It turns out that every cell in your body recognizes the active form of vitamin D. So you have to ask the question, 'Why would receptors for the active form of vitamin D be in your colon, breast, prostate, brain and immune cells?' "
The latest recommendation is for 1,000 IU of vitamin D each day.
Dr. Holick directs the Bone Health Clinic at Boston Medical Center and has recently published a book, The UV Advantage. But because of his position about limited, unprotected exposure to sunlight, he was recently asked to resign from BU medical school's dermatology department.
The new findings that attribute broad benefits to vitamin D are being unveiled just as widespread deficiencies are being detected. Physicians around the globe, for instance, are noting an increase in the number of infants diagnosed with vitamin D deficiency rickets.
A study by Susan Sullivan, PhD, a researcher at the University of Maine's food science and human nutrition department, found that 23 10- to 13-year-old girls in Maine registered vitamin D deficiencies during a three-year-period. Those deficiencies were occurring at an important bone-building stage in the young teens' lives.
Additionally, a conference was held last fall at the National Institutes of Health to assess the "alarming prevalence of low circulating levels of vitamin D in the United States population." Attendees are now completing papers to pinpoint areas of needed research.
Conference organizers speculated that the low levels of the vitamin, which is also a hormone, could be caused by lower intake of vitamin-fortified foods, particularly milk and cereal; an increase in the use of sunblock and decreased sun exposure; and increases in the numbers of exclusively breastfed infants.
Frank Greer, MD, University of Wisconsin professor of pediatrics, recommends that mothers give their infants supplements. He said his advice is not always heeded because of mistaken beliefs that breastfeeding supplies all necessary nutrition.
"There are, without question, some subpopulations in the United States that are really at risk," said James Fleet, PhD, associate professor of foods and nutrition at Purdue University in Indiana. "Those most at risk are either people who don't go outside very regularly or when they do go out there are things about them or where they live that make it virtually impossible for them to make vitamin D from sunlight."
This group includes people in the far north, those with dark skin, people
in nursing homes and those, particularly women, who cover up for religious
reasons. If these people don't, or can't get enough vitamin D from the
sun, supplements are recommended.
Too much? Not enough?
Amounts required to ensure bone health were established many years ago, but many experts now believe that those minimum daily requirements are too low.
Current recommendations call for 200 IU per day for men and women ages 19 to 50, 400 IU for those 50 to 69 and 600 IU for those older than 70.
Vitamin D deficiencies are linked to nonspecific bone and muscle pain.
These amounts are inadequate, said Reinhold Vieth, PhD, associate professor of pathology and laboratory medicine at the University of Toronto.
"It's like being a homeopath and saying if you take trace amounts of this nutrient, magic will happen," he said. Infants fare a bit better under current guidelines, as their supplements contain 200 IU to 400 IU of vitamin D.
As a result of recent attention, many vitamin D supporters have settled on a recommendation of 1,000 IU per day for adults. A consensus emerged among experts assembled in Switzerland in May 2003 that this is the amount recommended for preventing osteoporosis.
Since there are only about 100 IU in a glass of milk or fortified orange juice, and about 360 IU in a 31Ž2 oz. serving of salmon, tablets containing vitamin D3, or cholecalciferol, could be the most realistic method to boost intake.
But although large-dose supplements are available in Canada, Dr. Vieth noted, 1,000 unit doses are not easily obtained in the United States.
Meanwhile, even though there are always concerns about people taking toxic doses of vitamin D, most say that is unlikely to occur. "My perspective is that the fear of an overdose is grossly, grossly overblown," Dr. Vieth said.
The greater area of controversy and concern seems to center around the issue of increasing exposure to sunlight to boost vitamin D.
Clearly, most dermatologists would prefer that their patients get their vitamin D from supplements. Their preventive message to avoid all exposure has fallen on deaf ears, they say, and weakening that message could only make matters worse.
Despite their mantra about the importance of donning wide-brimmed hats and long sleeves and slathering on sunscreen liberally and frequently, people are going to indoor tanning salons and the beach more frequently than they did 10 years ago, said James Spencer, MD, a dermatologist at Mount Sinai School of Medicine in New York City.
"Skin cancer used to be something we saw in old people," Dr. Spencer said. "Now I'm seeing it in people in their 20s."
Who may need extra Vitamin D?
Information on vitamin D from the National Institutes of Health (clinicalcenter.nih.gov/ccc/supplements/vitd.html)
The American Academy of Pediatrics recommendations for vitamin D supplements (www.aap.org/advocacy/archives/aprvitamin.htm)
Vitamin D recommendations from the National Osteoporosis Foundation (www.nof.org/prevention/calcium.htm)
Vitamin D Council (www.cholecalciferol-council.com)
Vitamin D recommendations from the Osteoporosis Society of Canada (www.osteoporosis.ca/english/About
Copyright © 2004, American Medical Association