Folic acid and vitamins B6 and B12 play no significant role in preventing cancer in women at high risk for cardiovascular disease, said a study published Tuesday in the Journal of the American Medical Association.
The study contradicts a prevalent belief in the medical community about cancer prevention through intake of folic acid and vitamins B6 and B12.
Since 1998, many food items in the United States have been enriched with synthetic folic acid chiefly to reduce the risk of neural tube birth defects.
Around one third of the United States' adult population currently take multivitamin complexes that include folic acid and vitamins B6 and B12, the study said.
However, there are few clinical test results linking folic acid alone or in combination with vitamin B to the risk of cancer. Furthermore, the test results are not coherent and one of them even showed harmful effects, the researchers said.
"Combined folic acid, vitamin B6, and vitamin B12 treatment had no significant effect on overall risk of total invasive cancer or breast cancer among women during the folic acid fortification era," the study said.
The latest study was carried out among 5,442 female health professionals aged 42 years or older at high risk of cardiovascular disease.
Half the participants were randomly assigned to receive a daily combination of folic acid (2.5 milligrams), vitamin B6 (50 mg) and vitamin B12 (1.0 mg), while the rest were administered a placebo.
The clinical trial lasted from April 1998 to July 2005.