SCIENCE / PEDIATRICS : Research Links Colic to Cow Antibodies
Scientists believe they may have finally discovered a major cause of colic in breast-fed babies.
St. Louis researchers said Tuesday that cow antibodies in human breast milk may be the cause of the dreaded--but usually not serious--condition.
Pediatricians have long believed that similar cow proteins in infant formulas may trigger allergic reactions that cause colic, but have been puzzled that the digestive disturbance occurs with the same frequency, about 20%, in both formula-fed and breast-fed infants.
Researchers from the Washington University School of Medicine report in the current issue of the journal Pediatrics that mother’s milk can contain higher concentrations of the cow antibodies than formula. The finding was unexpected because researchers had believed that the antibodies in cows’ milk are destroyed by the human digestive system.
The antibodies apparently are destroyed in most women. The researchers found no antibodies in breast milk from mothers whose babies were not colicky. But in perhaps 20% of women, the antibodies survive through some as-yet unknown mechanism.
Colic, which affects an estimated 1 million infants a year, is characterized by tightened abdominal muscles and spitting up in infants, high-pitched crying and an inability to be consoled. It normally begins after about 2 weeks of age.
Although it is not life-threatening and normally resolves itself after three or four months, colic causes strong emotional distress among parents and has occasionally been implicated as a trigger for child abuse, said Washington University pediatrician Patrick S. Clyne, a co-author of the paper with immunologist Anthony Kulczycki Jr.
One key finding of the study is that cow antibodies can persist in a mother’s milk for as long as a week after she drinks cows’ milk. This discovery is particularly important, Clyne said, because the most common form of treatment is for the mother to stop consuming all dairy products, a reflection of the belief that colic is caused by something from cows’ milk, although doctors were not sure what.
“Our results suggest (mothers) may have to remain on a dairy-free diet for as long as 10 days for the results to become apparent,” he said.
Pediatric gastroenterologist Frank R. Sinatra of Childrens Hospital Los Angeles cautioned that “colic is a poorly defined syndrome that has no specific diagnostic criteria. . . . There are multiple causes of colic.” He acknowledged that the new results are “interesting.”
Clyne and Kulczycki, reasoning that the same chemical was probably the cause in both breast- and formula-fed infants, focused their investigation on antibodies.
“We were looking over what is in milk and what has been looked at and what hasn’t,” Clyne said. “About the only thing that hadn’t been looked at was antibodies,” probably because researchers believed the antibodies would be easily destroyed in the stomach before they could be taken up by the mother’s body.
They developed a special test for cow antibodies, called immunoglobulin G or IgG, and determined the levels of IgG in 124 breast-milk samples and 25 milk-based commercial formulas. They found that IgG levels were significantly higher in milk from 29 mothers who had colicky infants than in milk from mothers whose infants did not suffer from the disorder, as well as “much greater” than the concentrations of other cow proteins.