As evidence of widespread vitamin D deficiency grows, some scientists are wondering whether the sunshine vitamin—once only considered important in bone health—may actually play a role in one of neurology’s most vexing conditions: autism.
The idea, although not yet tested or widely held, comes out of preliminary studies in Sweden and Minnesota. Last summer, Swedish researchers published a study in Developmental Medicine and Child Neurology that found the prevalence of autism and related disorders was three to four times higher among Somali immigrants than non-Somalis in Stockholm. The study reviewed the records of 2,437 children, born between 1988 and 1998 in Stockholm, in response to parents and teachers who had raised concerns about whether children with a Somali background were overrepresented in the total group of children with autism.
In Sweden, the 15,000-strong Somali community calls autism “the Swedish disease,” says Elisabeth Fernell, a researcher at the Karolinska Institute in Stockholm and a co-author of the study.
In Minnesota, where there are an estimated 60,000 Somali immigrants, the situation was quite similar: There, health officials noted reports of autism among Somali refugees, who began arriving in 1993, comparable to those found in Sweden. Within several years of arrival, dozens of the Somali families whose children were born in the U.S. found themselves grappling with autism, says Huda Farah, a Somali-born molecular biologist who works on refugee resettlement issues with Minnesota health officials. The number of Somali children in the city’s autism programs jumped from zero in 1999 to 43 in 2007, says Ann Fox, director of special education programs for Minneapolis schools. The number of Somali-speaking children in the Minneapolis school district increased from 1,773 to 2,029 during the same period.
Few, if any, Somalis had ever seen anything like it. “It has shocked the community,” Farah says. “We never saw such a disease in Somalia. We do not even have a word for it.”
What seemed to link the two regions was the fact that Somalis were getting less sun than in their native country—and therefore less vitamin D. The vitamin is made by the skin during sun exposure, or ingested in a small number of foods. At northern latitudes in the summertime, light-skinned people produce about 1,000 international units (IUs) of vitamin D per minute, but those with darker skin synthesize it more slowly, says Adit Ginde, an assistant professor at the University of Colorado Denver School of Medicine. Ginde recommends between 1,000 to 2,000 IUs per day, calling current recommendations of 200 IUs per day outmoded.
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