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 Researchers found that moms of kids with autism were less likely to
remember taking iron supplements before and during pregnancy than
other moms. That alone is not enough to prove a link, however.
“Even though we found an association, it’s just an association and
needs to be replicated,” said lead author Dr. Rebecca J. Schmidt.
“If this is replicated, it will reinforce that women should be
following current specific recommendations for iron intake before
they get pregnant, during pregnancy and during breastfeeding,” said
Schmidt, who worked on the study in the department of public health
sciences at the School of Medicine at the University of California,
Davis.
Folic acid, or vitamin B, deficiency has also been linked to autism
risk. Both folic acid and iron are involved in fetal brain
development and are usually included in prenatal vitamins, but this
is the first time research has focused specifically on iron intake
and later autism risk, the authors write.
For the new study, Schmidt and her coauthors interviewed mothers in
California with children ages two to five about any multivitamins,
prenatal vitamins or supplements the mothers were taking before,
during and after pregnancy.
The researchers also asked about fortified cereals and other dietary
sources of iron.
They compared moms of 520 children diagnosed with an autism spectrum
disorder and mothers of 346 kids with typical development.
Moms in the typical development group were more likely to report
taking iron-specific supplements, and they had higher average daily
intakes, the researchers reported in the American Journal of
Epidemiology.
Prenatal vitamins were the biggest source of iron for mothers in
both groups, accounting for about 30 to 32 milligrams. The rest of
the iron came mostly from iron supplements, which reportedly were
used by about 31 percent of women with typically developing kids and
about 25 percent of mothers of kids with autism.
Overall, based on researchers’ estimates of daily iron intakes, moms
in the typical development group got 57 milligrams of iron per day,
on average, compared to 51 milligrams per day for moms in the autism
group.
But the moms in both groups were generally getting above the
recommended amount of iron, the researchers pointed out.
Typically an adult woman in her reproductive years should get 18
milligrams of iron daily, according to the Institute of Medicine.
During pregnancy, about half of women become iron deficient, so it’s
recommended they boost up to 27 mg per day, and get at least nine mg
daily while breastfeeding, Schmidt told Reuters Health by phone.
If the results of this study can be reproduced in other studies, it
might mean that the current recommendations for pregnant or
breastfeeding women are too low, the authors write.
According to the Institute of Medicine tables, the tolerable upper
intake level for adult men and women is 45 milligrams per day, but
other studies have found that pregnant women in the U.S. generally
get about 48 milligrams per day from supplements.
Too much iron from supplements can be toxic, Schmidt warned, but for
iron in the diet from fortified cereals, beans, red meat and dark
chocolate, there is no toxicity level.
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“I think most women know they’re supposed to take a prenatal vitamin
during and before pregnancy but not all women know why they’re
taking it,” she said.
Some prenatal vitamins include iron, but others, like the popular
gummy vitamins, do not. Iron can cause nausea, so some prenatal
vitamins leave it out for the woman to take separately at night
before bed, she said.
“Most women in America just don’t get quite enough iron from the
diet,” Schmidt said.
Since the new study only compared moms from two groups and asked
them all to remember what they had been doing two to five years
earlier, there is room for another explanation, she said. Lower
levels of iron may not have caused autism for the kids. But iron and
later autism were related somehow.
The association was especially important for women who were over age
35 and who had metabolic conditions like diabetes and obesity. That
could be because as women age they start to metabolize iron
differently, Schmidt said.
“The data here are very strong and internally consistent,” said Dr.
Philip J. Landrigan, who was not part of the new study.
Landrigan directs the Children's Environmental Health Center at the
Icahn School of Medicine at Mount Sinai in New York.
Women who are pregnant should be sure to take iron in addition to
folic acid, he told Reuters Health by phone.
Iron deficiency is very common in the population, and the autism
rate has been rising fast in recent years, and the two might be
connected, he said.
“I’m sure it’s not the whole story, because iron deficiency has been
around a long time,” he said.
The study adds to the growing body of evidence that non-genetic risk
factors can contribute to autism risk and showed that combinations
of factors, like maternal age and metabolic conditions, don’t just
add together, but seem to have a significantly bigger impact on
risk, said Cindy Lawler, chief of the Genes, Environment, and Health
Branch at the National Institutes of Environmental Health Sciences
in Research Triangle Park, North Carolina.
“The best advice for mothers right now is to get individual guidance
on nutrition and supplement use from their physicians,” she told
Reuters Health by email.
SOURCE: http://bit.ly/Y1WPuS
American Journal of Epidemiology, online September 22, 2014.
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