News Stories in Perspective

Folate: Helpful or Harmful for Cancer Prevention?

A recently published Swedish study links higher intake of folate, a B vitamin required to safeguard our DNA, with lower risk of postmenopausal breast cancer. This is just the latest among multiple studies suggesting that folate may help reduce risk for cancers of the colon, pancreas, esophagus, stomach, breast and cervix. However, with other research showing that too much folate can promote cancer development, where does the line fall between benefit and possible harm?

Folate, involved in the creation and repair of DNA, is critical in ensuring that our bodies’ genetic instruction manual is read correctly. Damaged DNA can create changes in genes that facilitate the growth and development of cancer cells. Connect the dots and it’s easy to see why so much research is focused on the folate-cancer link.

In the aforementioned report from the Swedish Malmo Diet and Cancer Study, women whose diets were highest in folate (rich sources include dark green leafy vegetables, dried beans and fruit) were 44 percent less likely to develop postmenopausal breast cancer than women who ate the least folate over the nearly ten-year study. Those with highest total consumption of folate from foods plus folic acid (the form found in supplements and fortified food) showed a similar 41 percent reduced risk when compared to subjects with the lowest intake.

But the evidence is not always so straightforward. An analysis of 23 studies on folate and breast cancer risk found mixed results. When women were separated according to alcohol consumption, however, dietary folate had no impact on breast cancer risk among subjects who rarely or never drank alcohol. Conversely, women who drank moderately (or more) and had a high folate intake reduced their breast cancer risk by almost 50 percent. This difference was noted even among those women who consumed one drink a day – an important finding since conflicting research suggests that even moderate drinking can increase breast cancer risk; perhaps a diet high in folate can mitigate some of this risk among women who consume alcohol.

Yet, as is the nature of the scientific process, another analysis of 22 studies relating folate consumption to breast cancer risk found little if any impact. The former analysis investigated whether inherited differences might make folate more important for some women than others. Such difference, namely in the way our genes regulate folate metabolism, might explain why folate has an impact on cancer risk for some but not others (such a genetic discrepancy has already been noted for colon cancer). In the case of breast cancer, however, researchers were unable to show a genetic link.

Still, other research is raising concerns that getting too much folate could promote cancer development. Laboratory studies suggest that once a small tumor or polyp has formed, extra folate may actually encourage the aggressive growth of cancer cells and silence so-called suppressor genes. Findings from the Aspirin/Folate Polyp Prevention Study seem to support this hypothesis. Among nearly 1000 men and women who previously had colon polyps removed, those assigned to take 1000 micrograms (mcg) of folic acid developed 67 percent more advanced polyps than those taking an inactive placebo. Note, however that the supplements taken were more than two-and-a-half times the recommended target for adults.

The bottom line: in the case of folate, research suggests that too much of a good thing may be detrimental. But take heart – eating a healthy plant-based diet will not put you at risk for excess folate. In the end, be mindful of vitamin supplements and certain nutrition bars or cereals that provide 50 percent or more of the Daily Value for folate; you’d be surprised at how quickly they can add up. Instead, choose natural food sources of folate that also provide the beneficial vitamins, minerals and phytochemicals needed for overall cancer protection.