A new study has reported that folic acid reduces the expression of beneficial tumor suppressor genes in breast cancer cells.

Food sources of folate

Most U.S. breast cancer patients and survivors with a healthy diet are not likely to be deficient in folate and would not benefit from taking folic acid. In fact, the effects of folate occurring naturally in food may be different from those of folic acid supplements. Therefore, we suggest that breast cancer survivors include foods in their diets that incorporate folate rather than taking folic acid. The following foods are good sources of folate, as well as being associated with reduced risk of breast cancer:

Beans, dry
Bell peppers
Broccoli
Cabbage
Cauliflower
Celery

Collard greens
Lettuce, romaine
Liver, chicken or turkey
Mustard greens
Parsley
Squash

Note that both green and black tea reduce intestinal absorption of folate and should not be consumed simultaneously with high-folate foods by those wishing to increase their folate levels.

Latest research finds folic acid turns off tumor suppressor genes

The study referenced at the beginning of this news article was designed to investigate the influence of folic acid on tumor suppressor genes (which suppress or block the development of cancer). To conduct the study, the authors tested the effects of folic acid in hormone receptor positive MCF-7 and triple negative MDA-MB-231 breast cancer cell lines with varying degrees of invasive capacity. Expression of PTEN, APC and RARbeta2 tumor suppressor genes, which encode proteins involved in regulation of oncogenic intracellular signaling pathways, were measured. Increasing concentrations of folic acid were found to result in a down-regulation of tumor suppressor genes in a dose-dependent manner. The effects were strongest in ER+/PR+ MCF-7 cells. The authors conclude that caution needs to be used when using folic acid supplementation since it may lead to cancer progression.