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To the Editors:

The past few years have seen a large influx of Muslims into western Europe, causing some cultural clashes. Recently, traditional dress has been one focus of such clashes. Is wearing the veil a mark of religious freedom, or by allowing it are governments denying Muslim women and girls equality with their non-Muslim peers? (1). In November 2006, Jack Straw, the former foreign secretary of England, declared that wearing the niqab (veil) made relations between Muslims and non-Muslims more difficult because it was “such a visible statement of separation and difference” (2). The United Kingdom is not the only country in Europe caught up in this cultural debate. In February 2004, the French National Assembly approved a new law prohibiting “the wearing of signs or dress by which students ostensibly express a religious belonging” in the nation's public schools (3). Other people, such as nuns and orthodox Jews, also cover most of their bodies for religious reasons.

But more is at stake than just religious and personal freedom. Covering the skin is a risk factor for vitamin D deficiency. Although currently the World Health Organization places greater emphasis on overexposure to ultraviolet (UV) light than underexposure, there is an increasing emphasis on the prevention of vitamin D deficiency. Populations typically at risk for low sun exposure are institutionalized individuals, deeply pigmented people living in low ultraviolet settings such as high latitudes, and those who, for religious or cultural reasons, cover their entire body surface when they are outdoors (4).

The primary source of vitamin D is sunlight, which allows the cutaneous synthesis of vitamin D. In locations where there is limited sunlight for much of the year, such as northern Europe, it is difficult to maintain an optimal vitamin D level through diet alone. Lack of vitamin D is the most common cause of rickets. However, even in some of the sunniest areas of the world rickets is a major health problem because wearing clothing that covers most of the skin is a common practice. As many as 35–80% of children in Saudi Arabia, India, Turkey, Israel, and Egypt are vitamin D deficient (5). Most European countries do not supplement milk with vitamin D.

Vitamin D is necessary for absorption of calcium and maintaining a calcium and phosphorus balance. Since the vitamin D content of breast milk is low, the vitamin D status of breast-fed infants is dependent on vitamin D gained across the placenta, which is low in women with low vitamin D levels (6). The consequences of vitamin D deficiency are life-long. Children who are born to mothers who have low vitamin D levels are more likely to develop rickets (7). Adults develop osteomalacia (painful bones) as a result of a decrease in bone mineralization. There is increasing evidence that implicates vitamin D deficiency with an increased risk of type I diabetes, multiple sclerosis, rheumatoid arthritis, hypertension, cardiovascular heart disease, and cancer (8), as well as muscle weakness in the elderly (9).

Many questions about vitamin D remain unanswered. The optimal level of vitamin D to maintain bone health is known, but the threshold for the other possible beneficial effects of vitamin D is not (10). Epidemiologic studies should eventually give us these answers. Also germane to this discussion is the assumption that oral supplements of vitamin D have equivalent health benefits to UV sun exposure, as this has important implications for public health. For years, the message from the health care industry has been to avoid sunlight in order to prevent skin cancer. The American Cancer Society and the Canadian Cancer Society, in collaboration with several other interested parties, are formulating a policy statement for the lay public and professionals outlining how to achieve adequate vitamin D levels safely (11). In 2005, Bischoff-Ferrari et al conducted a meta-analysis of randomized controlled trials and found evidence that vitamin D supplementation appears to reduce the risk of hip and nonvertebral fractures in ambulatory or institutionalized elderly people (12). More research needs to be done to document the hazards to the at-risk population and the potential benefits of maintaining optimal vitamin D.

The medical community has an ethical responsibility to educate the public about vitamin D. Vitamin D is vital for maintaining bone health, and new research is documenting the importance of vitamin D in the health of both the immune system and muscle. Yet the public health message is complex. The safe dose of sun exposure is unknown and may differ depending on skin pigment. The optimal level of vitamin D and the best way to achieve it have not yet been determined. We do know that certain populations, including those who cover most of their skin when outdoors, are at risk for vitamin D deficiency. Sensitivity to cultural practices is extremely important so that the issue of vitamin D deficiency does not become politicized. Governmental policy and health policy makers will have to decide whether food fortification or supplements are the best way to achieve adequate vitamin D levels.

Michele Meltzer MD*, * Bioethics University of Pennsylvania, Philadelphia.