Prenatal multivitamins with folic acid appear to cut kids' cancer risk: study

Canadian Press

02-22-07

TORONTO (CP) - Women who take vitamins containing folic acid before and during pregnancy appear to significantly cut the risk that their infants will develop three common childhood cancers, Canadian researchers say.

Folic acid is already known to diminish the chance that a child will be born with spina bifida or other neural tube defects, but it may also have powerful effects in preventing some cases of pediatric leukemia, brain tumours and neuroblastoma, the study by researchers at Toronto's Hospital for Sick Children suggests.

"I think this is another piece of evidence that suggests that prenatal vitamins that include folic acid should be taken by women who plan to become pregnant," said principal investigator Dr. Gideon Koren, director of the Motherisk Program at Sick Kids. "Because in addition to (neural tube) malformations, it seems to prevent a large proportion of common cancers in young children."

"This affordable approach could contribute to a significant reduction in the number of childhood cancer cases diagnosed each year, which has huge implications for society at large."

Leukemia, the most common childhood cancer, accounts for up to 35 per cent of new pediatric cases each year; brain and spinal tumours, the second most common form of cancer, account for 17 per cent; while neuroblastoma, the most prevalent solid tumour that occurs outside of the brain in children under age five, affects one in every 6,000 to 7,000 children in North America.

To conduct the study, Koren and his team pooled the data from seven studies that compared cancer rates in young children whose mothers reported taking prenatal multivitamins fortified with folic acid with those of children whose moms did not take the supplements.

The research, known as a meta-analysis, was published online Wednesday in the journal Clinical Pharmacology and Therapeutics.

The analysis found that prenatal supplementation with multivitamins containing folic acid is associated with a 39 per cent protective effect for leukemia, 27 per cent for brain tumours and 47 per cent for neuroblastoma.

Neuroblastoma arises in the adrenal gland or related nervous system tissue and can spread to the area behind the eyes and to the bones. The tumours may press on the spinal cord, causing paralysis. Often the cancer is present at birth but it not detected until later in infancy or childhood.

The apparent capacity of folic acid to prevent neuroblastoma was demonstrated in a 2003 study by Koren's group, which found that the incidence of the childhood cancer in Ontario dropped by more than half after new federal regulations in 1997 required that all flour be fortified with the B vitamin.

Dr. Paul Rogers, head of pediatric hematology-oncology at the B.C. Children's Hospital, said the meta-analysis confirms the results of the individual studies and actually strengthens the validity of their message.

"And I think it is something that should be propagated," said Rogers, who was not involved in the study. "I think this is a potential prevention. It's not a total prevention, but it is an additional clue that one can reduce the risks."

Yet, the study's message could have an unwanted side-effect: leading mothers whose children developed any of these cancers to blame themselves for not taking enough vitamin supplements or any at all before or during pregnancy. (Studies have shown that only half of Canadian women take adequate prenatal vitamins.)

But doctors stress that the causes of cancer are multifactorial and it's not known exactly what role folic acid alone plays - or, indeed, the contribution of other components of multivitamins.

"One may argue that women who take prenatal vitamins may do many other good things health-wise," Koren said.

Rogers said factors such as diet as well as exposure to viral infections or environmental toxins could also be responsible for planting the seeds of these childhood cancers, but more research is needed.

"And so, yes, (folic acid) does reduce the risk," he said. "But would it have reduced the chance to an individual child? No, you don't know, because there are other factors that as yet are unknown that may be causative in the development of a cancer in a child."

Koren said folic acid appears to "prevent some initiating events of cancer" that affect both children and some adults.

"It almost looks too simple, but if you look at other areas of public health, it's not the only example that simple things make a difference," he said.

Besides finding that folic acid could prevent neural tube defects, scientists figured out that ASA given to children and teens during a viral infection could cause Reye's syndrome, a potentially fatal condition that damages the liver and brain.

Twenty years ago, doctors warned that children and adolescents should not be given ASA, Koren said. "And 20 years later, we don't see Reye's syndrome anymore."