A new research report from Iran suggests that the eightfold rise in the incidence of multiple sclerosis, mainly in women, over the last 20 years may be related to an insufficient vitamin D supply due to the requirement for women to wear a veil in public.
In the report, researchers speculated that there may be a link between the significant (8.3-fold) increase in the incidence of multiple sclerosis (MS), mainly in women, between 1989 and 2006, and the Iranian Revo- lution, which led to drastic cultural changes (1). For example, it became a government requirement for women to wear loose-fitting clothing and a veil in public. Previous research has shown that veiled women have lower vitamin D levels compared to unveiled women (2). Without direct sun exposure to the skin, the body is unable to make vitamin D, which can increase the risk of developing MS. Thus, women in Iran are getting much less vitamin D now than prior to the Iranian Revolution, which took place in 1979. Given that the average age of MS onset is 30 and that the incidence of MS in Iran is the highest ever recorded just over 30 years after the revolution, there is a likely association between the Iranian revolution and reduced sub- sequent vitamin D levels, particularly in pregnant women, according to the researchers. Lifestyle changes, such as urbanization and use of sunscreen, may have to some extent contributed to increased vitamin D deficiency. However, these changes are unlikely to contribute to the particularly high increase in MS inci- dence observed in Iran as they occurred across the developed world and there is no evidence to suggest that they were particularly great in Iran.
The researchers concluded that preventing vitamin D deficiency by sufficient vitamin D intakes is a critical public health issue for Iranians both within and outside of the country, and could help prevent an emerging MS epidemic in this population. A number of studies have shown that one crucial environmental factor for MS risk is the degree of sunlight exposure one receives, which is linked to the vitamin D supply (3). In low-sun- light conditions (i.e. countries of high latitudes), insufficient vitamin D is produced, providing a risk factor for MS development. Ultraviolet (UV) light intensity is greater at high altitudes, resulting in a greater synthesis of vitamin D, which explains the lower MS rates usually found in countries at higher altitudes. However, clothing styles that conceal skin from ultraviolet sun radiation contribute to vitamin D deficiency, especially in veiled females. Research continues to show a clear link between vitamin D deficiency and an increased risk of MS. Some intervention studies also show that vitamin D supplementation may be able to help prevent or slow progression of MS (4).