Folate intake lowers colorectal cancer risk in women

Folate intake, whether in total or synthetic form, leads to a reduction in overall colorectal cancer (CRC) incidence following long latency periods, according to a US study. No evidence shows that high folate intake in the postfortification period is associated with a higher CRC risk in the female population.

“[C]oncerns have been raised about the potential for cancer promotion with excessive folate intake, especially after the mandatory folic acid fortification in the United States in 1998,” the authors said.

In this study, 86,320 women from the Nurses’ Health Study (1980–2016) were prospectively followed to assess the relationship between folate intake in different chemical forms and CRC risk, particularly in the postfortification era in the US.

The authors collected folate intake using validated food frequency questionnaires. CRC was self-reported and confirmed by review of medical records. Cox proportional hazards regression was used to examine the association between folate intake and CRC risk.

A total of 1,988 incident CRC cases were documented during follow-up. In analysis of folate intake as a continuous variable, greater total folate intake 12–24 years prior to diagnosis correlated with a lower risk of CRC (per increment of 400 dietary folate equivalents (DFE)/day: hazard ratio [HR], 0.93, 95 percent confidence interval [CI], 0.85–1.01 for 12–16 years; HR, 0.83, 95 percent CI, 0.75–0.92 for 16–20 years; HR, 0.87, 95 percent CI, 0.77–0.99 for 20–24 years).

Additionally, greater synthetic folic acid intake 16–24 years before diagnosis correlated with a reduced risk of CRC (per increment of 400 DFE/day: HR, 0.91, 95 percent CI, 0.84–0.99 for 16–20 years; HR, 0.91, 95 percent CI, 0.83–1.01 for 20–24 years).

In the postfortification period (1998–2016), no association was noted between CRC risk and intake of total or specific forms of folate, even among multivitamin users.