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Slight Yellow Tint May Be Protective for Newborns

Mon Nov 25, 5:41 PM ET
By Alison McCook

NEW YORK (Reuters Health) - Babies may develop jaundice--a yellowish color in the skin and eyes--after birth as a mechanism to protect their bodies against damaging substances called free radicals, new research suggests.

All babies' and adults' bodies contain mechanisms that protect them against this type of damage, study author Dr. Solomon H. Snyder of Johns Hopkins University in Baltimore, Maryland, told Reuters Health. However, the current findings suggest that many babies get an extra boost of protection from the yellowish pigment bilirubin that accumulates in their bodies. The pigment serves as an antioxidant, but also renders them slightly jaundiced.

He cautioned that babies who aren't jaundiced at birth are not in trouble. But Snyder added that doctors may want to reconsider immediately treating babies with slightly higher levels of bilirubin in their bodies after birth.

"This would suggest, you shouldn't worry too much" about light jaundice in newborns, Snyder said.

Bilirubin is a substance formed when old red blood cells and other body components that contain heme are broken down. Jaundice occurs when bilirubin builds up in the blood rather than being excreted by the liver into the intestine.

Doctors have known for a long time that too much bilirubin can be bad for babies, but the purpose of small increases of bilirubin after birth have remained unclear. In healthy infants, bilirubin levels can rise to 15-20 milligrams per deciliter (mg/dL) of blood in the first week after birth, but severe jaundice--over 25-30mg/dL of bilirubin--can cause brain damage if left untreated.

Treatment for serious cases of jaundice usually involves phototherapy--exposing the infant to bright light, which causes the bilirubin to change into a compound that is easily excreted with urine.

To determine what the purpose of slight increases in bilirubin after birth might be, Snyder and his colleagues gathered a group of human cells in the lab and turned off the enzyme that makes bilirubin, then exposed the cells to free radicals.

According to their report in the early edition of the Proceedings of the National Academy of Sciences (news - web sites), cells without bilirubin became damaged and died. However, cells that were able to produce bilirubin were also able to survive a thousand-fold increase of the free radical-producing substance used in the previous experiment.

In an interview with Reuters Health, Snyder explained that bilirubin is particularly good at fighting free radicals in the body because it can recycle itself over and over again. When bilirubin mops up one free radical, he explained, it converts into a substance that, with the help of another enzyme, can be changed back into bilirubin.

In terms of why babies might need higher levels of bilirubin at birth than they do as adults, Snyder explained that, in many ways, it's harder on the body to be a newborn than an adult. "You don't have to be a scientist to just think for a second of the radical change in the environment of the womb to that of outside," he said. Bilirubin is not currently sold in stores, Snyder said, but previous research has suggested that extra--but less than dangerous--levels of bilirubin might lessen the effect of stroke and even reduce the risk of cancer or heart attack. As such, he noted, it's reasonable to think that, one day, a pill that gives people an extra boost of bilirubin might also improve their health

SOURCE: Proceedings of the National Academy of Sciences
2002;10.1073/pnas.252626999