FRIDAY, Dec. 10, 2004 (HealthDayNews) -- A British study has found a possible link between taking folic acid supplements late in pregnancy and an increased incidence of breast cancer decades later.
But the researchers themselves state that the finding should be viewed with considerable caution.
"It is quite possible that this is a chance finding," said Dr. Andy R. Ness, a senior lecturer in epidemiology at the University of Bristol, and lead author of the report in the Dec. 11 issue of the British Medical Journal. "What we have found needs to be interpreted very cautiously until there has been further research."
The finding comes from a study that enrolled almost 3,000 pregnant women in Aberdeen, Scotland, in a trial of folic acid supplements in the 1960s, a time when it was becoming evident that taking the supplements reduced the incidence of birth defects such as spina bifida.
Women now are advised to take 400 micrograms a day of folic acid when they plan to become pregnant and continue to do so until the 12th week of pregnancy, but not longer; the birth defects it prevents occur early in pregnancy.
Some women in the Aberdeen study took much higher doses, 5 milligrams a day -- more than 10 times the currently recommended dose -- and all of them took the supplement right up to birth. The women who took supplements were found to have a higher incidence of breast cancer than women in the study who took a placebo. The effect was most noticeable among women who took the highest doses.
"But the number of cases is very small," Ness said. "We're talking about six or eight cases of breast cancer among almost 500 women over 35 years, when normally we might have expected four deaths. The only thing we can say for certain as a result of this research is that there needs to be further research."
An accompanying commentary by physicians at the Rollins School of Public Health at Emory University said "the most likely association for the reported association is chance."
A much larger study found that women who had a high intake of folic acid from food had a substantially lower risk of breast cancer than women with the lowest intake, said Dr. Godfrey P. Oakley, a research professor of epidemiology at Emory, and co-author of the commentary.
"If anything, folic acid prevents not only breast cancer but also colon cancer," he said. "The real tragedy is that in Europe, folic acid is not put into flour products, as is done in the United States."
Dr. Nancy Green, medical director of the March of Dimes Birth Defects Foundation, said the new study does not change the organization's positive view of folic acid supplements.
"We are staunch supporters of the benefits of folic acid for the prevention of birth defects," Green said. "There is ample evidence that taking folic acid before and early in pregnancy dramatically decreases the risk of neural tube defects, and mounting evidence that it also prevents other birth defects."
Because half of all pregnancies are unplanned, the March of Dimes recommends that "if you are capable of being pregnant, you should start taking folic acid, and continue to take it into your pregnancy," Green said.
For more on folic acid, visit the March of Dimes.