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# Folic acid may negate 5-fluorouracil in treating colon cancer
- URL: https://www.foodconsumer.org/folic_acid_may_negate_5-fluorouracil_1109160454/
- Published: 2016-11-11T17:52:00.000Z
- Updated: 2026-09-22T16:31:10.000Z
- Description: In mice carrying human colon cancer grafts, 5-fluorouracil slowed tumor growth without folic acid, but at 4x supplemental folic acid treated tumors grew faster than untreated ones, and at 12.5x the drug's effect disappeared. The authors call this a possible public health concern.
- Author: Food Consumer
- Tags: Minerals, Nutrition, #vivvo-import

Friday Nov 09, 2016 (foodconsumer.org)- Folic acid is added to many foods in the name of protecting against birth defects. Folic acid (folate) supplements are commonly used and of those who diagnosed with colorectal cancer, more than 50% use folic acid supplements.

But a new study suggests that high intake of folic acid supplements could completely offset the anticancer effect of 5-fluorouracil (5-FU) against colon cancer. As a result of the folic acid supplementation at certain levels, colon tumor could grow faster when treated with 5-FU than untreated with this chemotherapy.

This is an animal study in which human HCT116 colon cancer xenografts were implanted in mice which were treated with 5-FU or 5-FU plus 4 or 12.5 times supplemental levels of folic acid.

As a result, folic acid and 5-FU significantly interacted to influence xenograft growth. Without folic acid supplementation, 5-FU significantly inhibited the growth of xenograft. 

When 4x supplemental levels of folic acid was used, 5-FU treated xenografts grew actually faster than untreated xenografts. At 12.5x supplemental levels, folic acid completed negated the anticancer effect of 5-FU.

At the supplemental levels, folic acid did not seem to affect cell proliferation, degree of necrosis and expression of the relevant genes in colon cancer cells treated with 5-FU.

The study concluded that FA (folic acid) supplementation may be detrimental to 5-FU chemotherapy of colon cancer and pose public health concern." (David Liu)

*Lisa Ishiguro, Michael Yang, Kyoung-Jin Sohn, Catherine J. Streutker, Andrea Grin, Ruth Croxford , Folic Acid Supplementation Adversely Affects Chemosensitivity of Colon Cancer Cells to 5-fluorouracil, Nutrition and Cancer, Volume 68, 2016 - Issue 5, Pages 780-790 | Received 27 Apr 2015, Accepted 08 Feb 2016, Published online: 13 May 2016*