More Folic Acid from Food or Supplements Equals More Reduced Risk of Colon Cancer
This study counters the false information that folic acid may increase the risk of colon cancer. This type of false information is being created, promoted and funded by medical/pharmaceutical industry sources in their effort to keep people unhealthy over the long term so that people need to buy more drugs. See also the section on my web site "Nutrition In the Press: Corrections."
Michael's Comment: This study confirmed a greater reduced risk of colorectal cancers and adenomas as the intake of folic acid from food or supplements increased. The study's authors included Walter Willet, of Harvard Medical School, probably the single most credible nutritional researcher in the world. It was funded by National Institutes of Health, National Cancer Institute, the Conquer Cancer Coalition of Massachusetts (EG), and the Prevent Cancer Foundation. The study is most interesting because it provides a solid counterbalance to recent sham studies that indicated that supplemental (synthetic) folic acid could increase the risk of colon cancer.
Total folate intake 12 to 16 years prior to diagnosis was found to be associated with a lower risk of colorectal cancer, while more recent folate intake was not found to be associated, and both long-term and short-term intakes of total folate were associated with a lower risk of colorectal adenoma, particularly 4-8 years before diagnosis. In addition, supplementation with multivitamins for over 15 years was associated with a lower risk of colorectal cancer, and supplementation for a shorter duration was associated with a reduction in risk of colorectal adenoma. The authors conclude, "Folate intake is inversely associated with risk of colorectal cancer only during early preadenoma stages."
They further said, "We did not observe an adverse effect of total folate or synthetic folic acid on risk of colorectal cancer or adenoma even during the folic acid fortification era."
This statement is important because it confirms the safety of taking "synthetic" folic acid, which is the type of folic acid found in my most multivitamins.
Lee JE, Willett WC, et al. Folate intake and risk of colorectal cancer and adenoma: modification by time. American Journal of Clinical Nutrition, 2011 April; 93(4): 817-25.
Background: Experimental and observational studies have suggested that folate may play dual roles in colorectal cancer risk depending on the timing and dose.
Objective: We examined the latency between folate intake and the incidence of colorectal cancer.
Design: We prospectively examined associations between folate intake assessed every 2 to 4 y by using validated food-frequency questionnaires and risk of colorectal cancer and adenoma in the Nurses' Health Study and Health Professionals Follow-Up Study, which included 2299 incident colorectal cancers and 5655 colorectal adenomas from 1980 to 2004.
Results: There was an association between total folate intake 12 to 16 y before diagnosis and lower risk of colorectal cancer (relative risk: 0.69; 95% CI: 0.51, 0.94; 800 compared with <250 ug folate/d), but there was no association between intake in the recent past and colorectal cancer risk. Long- and short-term intakes of total folate were associated with a lower risk of colorectal adenoma, with a strong association with intake 4 to 8 y before diagnosis (odds ratio: 0.68; 95% CI: 0.60, 0.78; 800 compared with <250 ug folate/d). The current use of multivitamins for >15 y, but not a shorter duration of use, was associated with lower risk of colorectal cancer; and a shorter duration of use was related to lower risk of adenoma. We did not observe an adverse effect of total folate or synthetic folic acid on risk of colorectal cancer or adenoma even during the folic acid fortification era.
Conclusion: Folate intake is inversely associated with risk of colorectal cancer only during early pre-adenoma stages.