Jan. 14, 2008 -- The traditional Mediterranean diet has plenty of benefits for health, but do those benefits extend to the womb?
In the upcoming issue of the journal Thorax, researchers from Greece's University of Crete report that children born to mothers who closely followed the traditional Mediterranean diet while pregnant were 45% less likely to develop an allergic disease before age 7.
The most protective dietary practices were found to be eating vegetables more than eight times a week during pregnancy, fish more than three times a week, and beans and other legumes more than once a week.
But U.S. government guidelines advise pregnant women to limit their fish consumption to just 12 ounces a week, or roughly two or three servings.
And in newly published guidelines aimed at preventing allergy and asthma in high-risk children, the nutrition committee of the American Academy of Pediatrics (AAP) reported that there is no convincing evidence linking a mother's diet during pregnancy to her child's risk for allergic disease.
Committee chairman Frank R. Greer, MD, tells WebMD that the new study makes many assumptions based on questionable methodology, and does not provide that evidence.
"This study is of interest, but it certainly doesn't prove anything," he says. "The preponderance of evidence tells us that a woman's diet during pregnancy has little impact on her child's risk for allergy and asthma."
Mediterranean Diet and Allergic Disease
The traditional Mediterranean diet includes lots of fruits, vegetables, whole grains, nuts, beans and other legumes.
It also includes moderate amounts of fish, dairy products, poultry and eggs, and very little red meat, according to the American Heart Association.
In an effort to assess the diet's impact on allergy and asthma risk, Leda Chatzi, MD, PhD, and colleagues followed 468 mothers from pregnancy until their children were 6 and a half years old.
The mothers and their children lived on the Mediterranean island of Menorca, Spain.
The women completed food-frequency questionnaires during pregnancy, and they reported on their children's diets later on. They were also asked about their children's allergy and asthma symptoms and the children were tested for reactions to six common allergens after age 6.
Roughly a third of the mothers were considered to have had a low-quality Mediterranean diet while pregnant, while two-thirds were judged to have had high-quality Mediterranean diets.
Based on this analysis, eating a high-quality Mediterranean diet during pregnancy was associated with an 88% reduction in persistent wheeze risk among offspring and a 45% reduction in allergic disease risk.
Chatzi tells WebMD that the findings must be duplicated, and more research is needed to understand why a Mediterranean diet may be protective.
"We know that fruits, vegetables, and legumes are high in antioxidants, and there is evidence that antioxidants protect against inflammatory diseases like asthma and allergies," she says.
Safe for Pregnant Women?
But it is not clear if eating a largely plant-based diet, with protein derived mainly from fish and eggs, is a good idea for pregnant women and their unborn babies.
A 1994 study found that pregnant women who followed the diet got only about a third of the daily recommended intake of iron.
Greer says the single best thing an expectant mom can do to reduce her child's risk for allergic disease is to plan to breastfeed exclusively for at least four months.
That was the main recommendation of the AAP nutrition committee in its new guidelines for preventing allergic disease, released just last week.
"The best evidence we have says breastfeeding helps protect high-risk children against asthma and allergies," he says.