Autism and Vitamin D
What If Vitamin D Deficiency Is a Cause of Autism?: Scientific American
What If Vitamin D Deficiency Is a Cause of Autism?
A few researchers are turning their attention to the sunshine vitamin as a
culprit, prompted by the experience of immigrants that have moved from their
equatorial country to two northern latitude locations
By Gabrielle Glaser | Friday, April 24, 2009 | 66
HELP FROM THE SUN? Some researchers are turning their attention to the amount of
vitamin D a mother and infant get to try to trace autism.
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:
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
It’s hard to definitively assess the extent to which Somali immigrant families
in Sweden and Minnesota are experiencing increased rates of autism. Somalia
doesn't have great records of the condition, says Rebecca Berkowitz, who works
for a United Nations–affiliated NGO called Global Education Motivators.
"Children in Somalia may not even be getting diagnosed with autism due to the
overall lack of awareness of the disorder," Berkowitz says, in a nod to the fact
that there is no Somalian word for it. And Swedish scientists have reported
autism rates overall have risen since they began studying the epidemiology of
the disorder in the mid-1980s—just as U.S. Centers for Disease Control officials
have noted an increase.
Still, proponents of the vitamin D–autism link say there is biological
plausibility to their theory. They cite a 2007 review by Allan Kalueff, a
researcher now at Tulane University, in Current Opinion in Clinical Nutrition
and Metabolic Care. That review—based on more than 20 studies of animals and
humans—concluded that vitamin D during gestation and early infancy was essential
for "normal brain functioning."
At the same time, the theory needs a lot of data to back it before others will
give it much credence, given how many other potential reasons there are for a
climb in autism rates. Even Kalueff says he isn’t sure how vitamin D could be
related to autism, even if it is an important player in the brain: "Discussions
around autism specifically may be a right step or a wrong step, but they should
not distract us from a much bigger picture."
Catherine Lord, the director of the University of Michigan at Ann Arbor's Autism
and Communication Disorders Center, says she finds the Swedish study intriguing.
"But it is going to be really important to replicate these findings," says Lord,
who has studied the disorder for 40 years and has been instrumental in
developing autism diagnostic instruments used in practice and research
worldwide. “We are talking about a small group of children with a lot of social
factors, including that these kids are very conspicuously different from your
average Swedish child, and being assessed by people who are from very different
culture." There is also the issue of consanguinity, she says, as many Somalis
marry cousins. "This doesn't mean the study is wrong," she says. "But we need
So Fernell and her colleagues are now measuring vitamin D blood levels in
mothers and children with autism of both Somali and Swedish origin and comparing
them with a control group of mothers and healthy children. She will not say how
many subjects the study includes, describe any preliminary results nor say when
it will be complete. Farah says Minneapolis researchers are now preparing to
study the vitamin D levels of pregnant Somalis, other ethnic groups and
Minnesotans of European stock. (That data is particularly hard to come by
because Vitamin D levels are not typically screened in pregnancy in the U.S.,
says Stacy Brooks, a spokeswoman for the American College of Obstetricians and
The other potential reasons for a climb in autism rates: There is increased
attention to the condition in the U.S., and Somalis are more likely to see a
doctor after moving here. Also, genes, studies have found, may play a role; a
number of papers, including a 1989 study of five Nordic countries and a 1995
British study, found that the concordance rate among identical twins was as high
as 90 percent. (Then there is the much-ballyhooed but ultimately disproved link
Somali refugees, in particular, faced multiple stressors as they adjusted to
their new lives in Sweden and Minnesota: They had fled civil war, lost a
supportive tribal culture, and replaced a diet of fruit, fresh meat and grains
with processed food. Perhaps, most importantly, they had traded family compounds
and regular exposure to the equatorial sun for cloistered high-rise apartments.
But some of those potential cultural reasons could also point to vitamin D.
Surrounded by strangers, the predominantly Muslim women covered themselves
almost continuously when outdoors, says Gregory A. Plotnikoff, medical director
of the Penny George Institute for Health and Healing in Minneapolis. Plotnikoff,
an internist, speaks Somali and has many Somali patients. That meant less
exposure to the sun for pregnant women, who would have worn less modest dress in
private areas of their own family compounds.
And there is other evidence for a vitamin D link: Last November, Cornell
University researchers published a study in Archives of Pediatrics & Adolescent
Medicine showing that children in rainy (and therefore more overcast) counties
of Oregon, Washington and California were two times more likely to be diagnosed
with autism than their counterparts in drier parts of the state. "Our research
is sufficiently suggestive of an environmental trigger for autism associated
with precipitation, of which vitamin D deficiency is one possibility," says
study co-author Michael Waldman, a professor of management and economics at
Cornell's Johnson Graduate School of Management. "Further research focused on
vitamin D deficiency is clearly warranted." His research on environmental links
to autism are ongoing; he plans to publish in the coming months but will not
disclose any of his studies until they are accepted by a journal.
Gene Stubbs, an associate professor emeritus of psychiatry and pediatrics at
Oregon Health & Science University, says the preliminary research is already
intriguing. "We don't have proof, but I am certainly leaning in the direction
that this hypothesis could be correct for a proportion of kids," says Stubbs,
who has been studying autism for 30 years. He is launching a pilot study of 150
pregnant women who have at least one child diagnosed with the disorder. The
women will receive 5,000 IUs of vitamin D3 during gestation and 7,000 IUs during
lactation. "If we find that we are able to reduce the recurrence rate of autism
within families substantially enough, others will want to study this in larger
groups with larger controls."Scientific American is a trademark of Scientific
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