The research in animals centers around diethanolamine (DEA), a chemical used in shampoos, lotions, creams and other cosmetics. DEA is used widely because it provides a rich lather in shampoos and keeps a favorable consistency in lotions and creams, but there's also some research that shows it may rob the brain of its ability to make memory cells.
"Depending on the treatment, some mice are stupid, some are not," said researcher Dr. Steven Zeisel.
In the modern scientific telling of the ancient story Samson was shampooed by Delilah and he became so dumb she was able to manipulate him to do her bidding without cutting off his hair.
The risk from this effect is much greater for fetuses and babies than for adult humans.
Dr. Zeisel says if the dea-hypothesis holds true, the memory impact would probably be minimal in adults. But it could have a bigger effect on the developing brain, during pregnancy and the first few years of life.
Dr. Zeisel is investigating whether choline supplementation can counteract the effect of DEA and TEA.
The US National Institutes of Health National Library of Medicine happens to have an online database of household products and their ingredients. Check out the lists of Shampoo/Conditioner and Shampoo products and what each contains. It doesn't appear that all products are listed. Also, the ingredient lists look like what you find by reading the side of the bottle anyway. Still, if you want to check a number of different products while still remembering the names of these chemicals it is pretty quick to do.
Now, working with nerve tissue derived from a human cancer known as a neuroblastoma, the UNC researchers have discovered why more choline causes stem cells -- the parents of brain cells -- to reproduce more than they would if insufficient choline were available.
A report on the findings will appear in the April issue of the
Journal of Neurochemistry. Authors are doctoral student Mihai D. Niculescu and
Dr. Steven H. Zeisel, professor and chair of nutrition at the UNC schools of
public health and medicine. Dr. Yutaka Yamamuro, a former postdoctoral fellow
in Zeisel's laboratory now with
"We found that if we provided them with less choline, those nerve cells divided less and multiplied less," Zeisel said. "We then went on to try to explain why by looking at genes known to regulate cell division."
Scientists focused on cyclin-dependent kinase inhibitor 3 genes, which keep cells from dividing until a biochemical message turns the genes off, he said. They found exactly what they expected.
"We showed that choline donates a piece of its molecule
called a methyl group and that gets put on the
But when the gene is under-methylated -- such as when there's not enough choline in the diet -- then it's turned on -- halting or slowing nerve cell division, he said.
"Nature has built a remarkable switch into these genes something like the switches we have on the walls at home and at work," Zeisel said. "In this very complicated study, we've discovered that the diet during pregnancy turns on or turns off division of stem cells that form the memory areas of the brain. Once you have changed formation of the memory areas, we can see it later in how the babies perform on memory testing once they are born. And the deficits can last a lifetime."
The next step, Zeisel said, will be confirm that the same things happen in living mouse fetuses when the mothers receive either high or low doses of choline.
Dr. Zeisel and other collaborators at UNC Chapel Hill and