Supplementation with folic acid during pregnancy may reduce the risk of the most common form of leukemia in children. A new study, published Saturday in Lancet, found a protective association between maternal folic acid supplementation during pregnancy and the occurrence of acute lymphoblastic leukemia (ALL).1 The new findings, while unexpected, further emphasize the importance of folic acid supplementation for all women of childbearing age.
Researchers studied children from Western Australia, 83 with ALL, ranging in age from less than one year to 14-years old, and 166 children of comparable ages without the disease. Nurses interviewed mothers about themselves and their children. Information gathered included demographic differences, family history, radiation exposure, use of medications, use of tobacco or alcohol, and other factors. Researchers sought to determine the effect, if any, of these various factors on ALL risk.
The researchers did not anticipate their findings. ALL was significantly associated with variables for which no previous association had been made: use of supplements containing folic acid and iron in pregnancy was associated with a 63% decrease in the risk of ALL. Of the 17 other drugs reviewed in this study, no other had any significant association.
ALL is the most common childhood cancer in developed countries. Although it has been previously associated with other risk factors, such as ionizing radiation and other environmental exposures, the number of known risk factors is few and meaningful preventive measures do not exist. This is the first study to find an association between nutrient supplementation and risk of ALL.
Although the study evaluated the combination of folic acid and iron, it is likely that folic acid was the protective agent. Unlike iron, a high dietary intake of folic acid has been associated with a decreased risk of other cancers such as colon cancer and some nervous system tumors.2 Moreover, the only striking previous association between iron and cancer is that excess iron may increase cancer risk.3
Folic acid is perhaps best known for preventing birth defects, such as spina bifida (a type of neural tube defect). In one study, women who were at high risk of giving birth to babies with neural tube defects were able to lower their risk by 72% by taking folic acid supplements prior to and during pregnancy.4 Both doctors and public health authorities recommend that all women of childbearing age supplement with 400 mcg per day of folic acid. If a woman waits until after pregnancy has been discovered to begin taking folic acid supplements, it will probably be too late to prevent a neural tube defect, since the nervous system forms in the early weeks of gestation, before most women know they are pregnant. On the other hand, folic acid may provide protection against ALL, even if it is started after pregnancy is discovered.
Beans, leafy green vegetables, citrus fruits, beets, wheat germ, and meat are good sources of folic acid. However, the amount of this vitamin in most diets is far less than the amount needed to exert the protective effects found in these studies. Therefore, folic acid supplementation is encouraged. Iron supplements should only be taken in consultation with a qualified healthcare practitioner.
1. Thompson JR, Fitz Gerald R, Willoughby MLN, Armstrong BK. Maternal folate supplementation in pregnancy and protection against acute lymphoblastic leukaemia in childhood: a case-control study. Lancet 2001;358:1935-40.
2. Giovannucci E, Stampfer MJ, Colditz GA, et al. Folate, methionine, and alcohol intake and risk of colorectal adenoma. J Natl Cancer Inst 1993;85:875-84.
3. Ulln H, Augustsson K, Gustavsson C, Steinbeck G. Supplementary iron and risk of cancer: reversed causality? Cancer Lett 1997;114:215-6.
4. MRC Vitamin Study Research Group. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. Lancet 1991;338:131-7