By Jan Bowers, contributing writer, May 02, 2011
Severe vitamin D deficiency, in the form of rickets, was first described by scientists in the mid-17th century. But not until the 1920s did researchers fully investigate both cod liver oil (a source of vitamin D) and ultraviolet radiation for the prevention and treatment of rickets, and identify vitamin D as the anti-rachitic agent. The fortification of milk with vitamin D eventually led to the eradication of rickets in the United States, and vitamin D became known as the “sunshine vitamin.”
Vitamin D is a fat-soluble vitamin that is naturally present in few foods. It can be obtained inexpensively through supplements, and is produced endogenously when exposure to sunlight triggers vitamin D synthesis. It promotes calcium absorption in the gastrointestinal tract and enables normal mineralization of bone, as well as bone growth and remodeling.
While the role of vitamin D in calcium absorption and bone health is broadly acknowledged, controversy surrounds other aspects of its use and its influence on overall health and specific disorders. What is the optimal blood level, and does it change with age? What are the health risks of falling below this level? What is the dietary intake needed to achieve this level? Is more better? Is exposure to sunlight necessary to maintain sufficient stores of vitamin D? [pagebreak]
As these issues are debated in the medical literature, in the media, and on the Internet, dermatologists are taking an active role — via policy statements, scientific presentations, and the counsel they offer to patients — in combating the perception that sun exposure and indoor tanning are necessary for any individual to maintain a sufficient level of vitamin D. “My patients have been hearing warnings about vitamin D insufficiency from the media or their primary care physician,” said Barbara A. Gilchrest, MD, professor and chair emeritus in the department of dermatology at Boston University. “There’s been a very vocal and passionate group of health professionals, nutritionists, and lay people who link all sorts of diseases — cancer, hypertension, diabetes, low birth weight — to so-called insufficient levels of vitamin D. From the medical side, all have recommended supplements — some quite large — with one notable exception from the academic community, who recommended limited sun exposure.” Other organizations, including the Indoor Tanning Association and the Vitamin D Council, have cited UV exposure as an acceptable means of obtaining vitamin D.
New recommendations from IOM, AAD
Amid the clamor about “epidemic” levels of vitamin D insufficiency in the U.S., the Institute of Medicine (IOM) issued a new public health report on dietary intake requirements for calcium and vitamin D in North America in late 2010. The report was designed to answer three questions, according to the authors: which health outcomes are influenced by vitamin D and/or calcium intake; how much calcium and vitamin D are needed to achieve desirable health outcomes; and how much is too much. Shortly after the IOM report was published, the American Academy of Dermatology amended its position statement on vitamin D to reflect the findings of the panel of 14 scientists who reviewed the data, said Henry W. Lim, MD, an author of the statement who serves as chair of the department of dermatology at Henry Ford Hospital and of the Academy’s Council on Science and Research. The Academy’s statement emphasizes up-front the known risks of skin cancer resulting from unprotected UV exposure and states that there is no safe threshold level of UV exposure that allows for maximal vitamin D synthesis without increasing skin cancer risk. [pagebreak]
“The IOM report is based on two very important conditions,” Dr. Lim said. “One is that the recommendations apply only to bone health. They looked at evidence for association between low vitamin D levels and various disease states, but the committee felt those data were inconsistent and inconclusive, and could not be used to make public health recommendations.” In addition to bone and skeletal health, the IOM committee reviewed evidence relating to cancer, cardiovascular disease, hypertension, diabetes, metabolic syndrome, falls and physical performance, autoimmune disorders, infectious diseases, neuropsychological functioning, and disorders of pregnancy. Randomized trial evidence for these conditions was sparse, the committee maintained, adding that “few clinical trials of calcium and/or vitamin D had been done with these extraskeletal outcomes as the primary prespecified outcomes.”
The second point the report emphasized is that the recommendation is “based on the assumption that individuals would have minimal or no sun exposure,” Dr. Lim said. “They acknowledge the fact that sun exposure is known to be associated with skin cancer, and they also avoid the confounding factors of skin types, because we know that individuals with darker skin would have less synthesis of vitamin D when they’re exposed to the sun.”
A dermatologist who regularly addresses the AAD annual scientific meeting on the topic of vitamin D and its surrounding controversies characterized the IOM report as “kind of agnostic” on the matter of sun exposure. “They didn’t say that they did or did not recommend that people get vitamin D from sun exposure,” said Kenneth Linden, MD, PhD, associate professor of dermatology at the University of California at Irvine. “To avoid over-broadening the scope of their considerations, the IOM simply said they are making the assumption that people will be protecting themselves from sunlight and will not be getting vitamin D from the sun. The AAD statement, with which I agree, on the other hand clearly says people should be protecting themselves from the sun. There’s a big difference there.” [pagebreak]
Recommended intake increases
The active form of vitamin D in the body, 1,25-Dihydroxyvitamin D (calcitriol), is not commonly measured due to its fluctuating levels and short half-life. Serum levels of 25-Hydroxyvitamin D (calcidiol, or 250HD), were considered by the IOM to be the “most useful” marker of vitamin D level. The IOM determined that serum 250HD levels of at least 20 ng/ml meet the needs of at least 97.5 percent of the population and that the long-term safety of levels above 50 ng/ml is unknown. That finding likely came as a disappointment to many vitamin D advocates, Dr. Linden said. “When the IOM met, many thought they would increase the level that’s considered sufficient in the blood. Several experts in the field of vitamin D felt it should be increased to 30 ng/ml. I agree with the IOM that there is insufficient evidence at this time that a higher level would lead to health benefits for the general population overall.”
The 50 ng/ml level cited by the IOM is troubling to a dermatologist who addressed the 2011 AAD annual meeting on vitamin D. “The IOM looked at a report on 250HD levels and cancer mortality in the National Health and Nutrition Examination Surveys study,” said Tissa Hata, MD, associate professor of dermatology at the University of California at San Diego. While the IOM cited 50 mg/ml as the level beyond which long-term safety is unknown, Dr. Hata suggested the data supports a lower limit. “There’s a U-shaped curve that indicates if you’re really low or really high you have an increased risk of cancer mortality. In men, mortality increased with a relative risk of 1.85 at serum levels greater than 40 ng/ml when compared to those less than 15 ng/ml. That scared me, to think that people might take 4,000 IU per day and not monitor their levels. Too much or too little vitamin D is not a good thing!” [pagebreak]
The IOM established a Recommended Dietary Allowance (RDA) of 400 IU per day for infants, 600 IU/d for individuals aged one to 70, and 800 IU/d for adults 71 and older. The upper intake levels — the highest daily intake that is likely to pose no risk — are 1,000 IU/d for infants up to six months, 1,500 IU/d for infants six to 12 months, 2,500 IU/d for children one to three, 3,000 IU/d for children four to eight, and 4,000 IU/d for individuals aged nine and older. “The IOM did increase the amounts by about 200 IU for most categories,” Dr. Linden said. “Many people heavily involved in vitamin D research feel that’s low, that it should be higher. Similarly, with the upper intake level of 4,000 IU, many researchers feel you could go up to 10,000 IU and be safe. I myself agree with the IOM recommendations — I would be concerned with intakes above 4,000 IU/day at this time, and I recommend the IOM RDAs as written.” Dr. Linden noted that “the IOM and AAD guidelines are based on current knowledge, and they recognize there is definitely a need for further research addressing the controversial areas. Future research will likely lead to further refinements of the guidelines in the future.”
Sun avoidance and supplements
In an editorial for the Journal of Investigative Dermatology (2010:130,321-326) entitled “What Is All This Commotion about Vitamin D?,” published several months before the IOM report, Dr. Gilchrest and Kavitha K. Reddy, MD, pointed to studies that show most daily sunscreen users “already achieve adequate or even maximal vitamin D in exposed skin during incidental exposures.” One reason, according to Dr. Gilchrest, is that few people use the amount of sunscreen specified by the manufacturer. “This means that you get between a 5 and 7 sun protection factor from applying SPF 100 as everyone applies it,” she said. “So 20 percent of the energy gets through, and it takes very little exposure to maximize the vitamin D production in your skin.” For those few patients who do use a thick layer of sunscreen, or who seldom go outdoors, “I think it’s well worth a multivitamin with 400 IU of vitamin D, and if they’re very concerned, up to 1,000 IU seems to be safe,” Dr. Gilchrest said. [pagebreak]
Like Dr. Gilchrest, Dr. Hata said her patients frequently bring up the topic of vitamin D in the course of an office visit. “A lot of people in California are asking to have their vitamin D levels tested, and I would say at least half of my patients are either already on a supplement or have been tested in the past year.” First and foremost, dermatologists need to counter the message that sunlight is an efficient method of obtaining vitamin D, Dr. Hata said. “We want to advise everyone to wear their sunscreen but they also may want to take an oral supplement. I think 1,000 IU per day is probably a good ballpark number for most people to take.”
It’s also important to remind patients to avoid indoor tanning, which is heavily promoted by salon owners and the Indoor Tanning Association as a source of vitamin D, Dr. Lim said. “It should be noted that the predominant emission of tanning lamp is in the UVA range, while cutaneous synthesis of vitamin D is only induced by UVB. We advise our patients to do sensible photoprotection and to ensure that they get adequate vitamin D. The simplest way is to follow the current recommendation of the IOM and take 600 IU per day, either in a multivitamin or a separate supplement.”
Dr. Linden said dermatologists should be “proactive to make sure patients are getting enough vitamin D through supplementation if we’re telling them to avoid the sun. There’s only so much time in a visit to do that, so a vitamin D pamphlet developed by the AAD would be helpful.” (Such a pamphlet will be available later this year.) He added that he orders vitamin D tests for patients who may be at risk of vitamin D deficiency, such as “those not taking vitamin D supplements who avoid the sun religiously, particularly if such patients are elderly with limited mobility and are likely to be limited to the indoors.”
Beyond counseling patients, dermatologists “have to step up and play a role in the medical discussion that’s going on in the country and world on how we should manage vitamin D,” Dr. Linden said. “Otherwise, we have some medical organizations saying you should get it through sunlight, others saying you shouldn’t, and that’s sending a confused message to the public. We should not be getting it through sunlight, and we need to make that point when this is being decided on a national policy level."
IOM report on vitamin D, Academy position statement available online
A brief summary of the IOM report is available at www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D/Report-Brief.aspx. The full report can also be purchased from this page. A longer summary appears in the January 2011 issue of the Journal of Clinical Endocrinology & Metabolism (pp.53-58).
The Academy’s position statement on vitamin D is available online. To find it, click on “Position statements” at www.aad.org/about-aad.