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SACN report on diet and colorectal cancer risk

SACN summary of report to CMO: Folic acid and colorectal cancer risk: Review of recommendation for mandatory folic acid fortification

In October 2009, the Scientific Advisory Committee on Nutrition (SACN) published a summary of its advice to the Chief Medical Officer for England (CMO) on folic acid and colorectal cancer risk.  Overall, SACN upheld its previous recommendation for the introduction of mandatory fortification with folic acid with controls on voluntary fortification.  However, SACN clarified its advice on folic acid supplement use for particular population groups.

The summary report is available here.  SACN will publish its full report at a later date, when the confidential results of a meta-analysis that was considered have been published by the researchers.

Background

SACN undertook this review in response to a request for advice from the CMO on potential adverse effects of folic acid on colorectal cancer risk.  The CMO requested this advice following the Food Standards Agency’s recommendation of June 2007 to the Minister of State for Public Health for mandatory fortification with folic acid to be introduced, alongside controls on voluntary fortification and advice on the use of supplements.

The purpose of mandatory fortification with folic acid is to reduce the number of neural tube defect affected pregnancies.  SACN estimated that there are between 700 and 900 pregnancies affected by neural tube defects each year in the UK.

Evidence reviewed

SACN members along with co-opted members from the Committee on Carcinogenicity and experts in cancer epidemiology undertook the review. 

The group considered three pieces of research in depth:

  1. Cole et al. (2007) – a double-blind randomised controlled trial in the USA that investigated the potential of folic acid supplementation with or without aspirin for prevention of new colorectal adenomas in persons with a recent history of colorectal adenomas;
  2. Mason et al. (2007) – an ecological study that suggested a temporal association between folic acid fortification and an increase in colorectal cancer incidence in the USA and Canada; and
  3. Confidential unpublished data – a meta-analysis of 35,603 individuals from seven randomised controlled trials of B-vitamins and cardiovascular disease risk, which also collected data on cancer outcomes.

 

The studies by Cole et al. (2007) and Mason et al. (2007) suggest that folic acid may increase the risk of colorectal cancer.  Conversely, the meta-analysis found that folic acid did not have a statistically significant effect on cancer incidence in men or women.  However, the group agreed that a link between folic acid and increased cancer risk could not be excluded, as the meta-analysis had limited statistical power to detect an effect.

Revised recommendations

As a result of this review, SACN has made the following key public health recommendations:

  • Advice about folic acid supplementation for pregnancy remains the same – all women who could become pregnant should take 400 µg/day folic acid as a medicinal or food supplement prior to conception and until the twelfth week of pregnancy (and 5 mg/day for those women with a previous pregnancy affected by a neural tube defect);
  • Mandatory fortification should only be introduced in the UK if it is accompanied by: (1) action to restrict voluntary fortification for foods with folic acid, (2) monitoring of emerging evidence on any adverse effects, and (3) guidance on supplement use for particular population groups.
  • If mandatory fortification is introduced, the recommendation relating to folic acid supplementation for pregnancy should remain.
  • As a precaution, people over the age of 50 years and/or those with a previous history of colorectal adenomas should not consume supplements containing folic acid exceeding 200 µg/day without medical guidance.  This recommendation is relevant now and in the event of mandatory folic acid fortification.

Looking ahead

The decision about whether mandatory folic acid fortification should be introduced in the UK now lies with the CMO and UK Health Ministers.  It is not clear when they will make their decision.  However, if mandatory fortification is approved then the relevant UK health departments will be responsible for producing an implementation plan.

References

Cole BF, Baron JA, Sandler RS et al. (2007) Folic acid for the prevention of colorectal adenomas: a randomized clinical trial. JAMA 297(21):2351-9.
Mason JB, Dickstein A, Jacques PF et al. (2007) A temporal association between folic acid fortification and an increase in colorectal cancer rates may be illuminating important biological principles: a hypothesis. Cancer Epidemiol Biomarkers Prev. 16(7):1325-9.

Last reviewed December 2010. Next review due January 2013. 

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