An ingredient found in many shampoos and other personal care products appears to interfere with normal brain development in baby mice when applied to the skin of pregnant mice, University of North Carolina at Chapel Hill researchers have discovered.
When Diethanolamine (DEA) was applied to the skin of pregnant mice, the fetuses showed inhibited cell growth and increased cell death in an area of the brain responsible for memory - the hippocampus.
Previous research on DEA has focused on its potential as a carcinogen. The current study is the first exploration of the compound's affect on brain development.
The finding needs further study and should not cause undue alarm, said Dr. Steven Zeisel, Kenan Distinguished University Professor of nutrition in UNC's schools of public health and medicine and associate dean for research in the School of Public Health.
"I don't believe any woman who's been using these products needs to have a sleepless night about having caused harm to her child," Zeisel said.
"At this point it is a caution," he added. "But it would probably be prudent to look at labels and try to limit exposure until we know more."
The study is featured as the cover story in the August issue of the FASEB journal, published by The Federation of American Societies for Experimental Biology.
In addition to Zeisel, other authors of the study are UNC nutrition research analyst Corneliu N. Craciunescu and postdoctoral research associate Dr. Renan Wu.
DEA appears to block the body's ability to absorb the nutrient choline, which Zeisel has previously reported is essential for normal development of the brain. A pregnant woman requires extra choline so that she can pass the nutrient on to the fetus. "You need choline to build a baby," Zeisel said.
More than 100,000 tons of DEA are sold in the United States each year. It is used as a wetting or thickening agent in not only shampoos but also such products as hand soaps, hairsprays and sunscreens.
Other names for the compound include Lauramide diethanolamine, Coco Diethanolamide, coconut oil amide of diethanolamine, Lauramide DEA, Lauric diethanolamide, Lauroyl diethanolamide, and Lauryl diethanolamide.
A list of some products that contain DEA can be found at http://householdproducts.nlm.nih.gov/index.htm.
The dose of DEA a person might get from shampooing is at least 10 times lower than the dose found to interfere with brain development in the study, Zeisel said.
Whether the amounts most people absorb from personal care products would cause harm remains unclear. Zeisel and colleagues are now doing further work to find out the lowest dose that causes an effect in mice, a process that could take about a year, he said.
The researchers also are exploring DEA's effect on other areas of the brain and are testing the effects of other compounds used in personal care products.
At very high doses, DEA treatment resulted in spontaneous miscarriages. "We saw smaller and smaller litters as we gave higher doses. No one has ever noted that before," Zeisel said.
"This agent not only affects brain development, but at higher doses probably affects some other development in a way that is fatal to the fetus," he said.
The study was funded by the National Institutes of Health.
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