Folic Acid Does Not Prevent Colorectal Tumours New Study Suggests
Featured ArticleMain Category: Colorectal Cancer
Also Included In: Nutrition / Diet; Clinical Trials / Drug Trials
Article Date: 06 Jun 2007 - 0:00 PST
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A new US study suggests that folic acid supplementation does not reduce the risk of benign colorectal tumours and may even increase the risk of higher grade tumours.
The study is published in the Journal of the American Medical Association (JAMA).
Some epidemiological and animal studies have suggested that folic acid supplementation may prevent colorectal tumours.
Dr Bernard F Cole of Dartmouth Medical School, Hanover, New Hampshire and colleagues conducted a nine-centre trial in the US and Canada between 1994 and 2004 involving 1,021 patients of average age 57 who had recently had at least one colorectal adenoma removed within three months of enrollment but with no history of colorectal cancer.
Adenomas or polyps are benign growths that form singly or in clumps and may become malignant over time.
The patients were randomly assigned to receive either folic acid supplement (1 mg per day) or placebo and underwent colonoscopy about 3 years afterwards. 607 of the patients had a second colonoscopy at the 6 year mark.
Cole and colleagues were surprised to find more adenomas in the patients who had received folic acid although the risk did not differ significantly between the two groups.
At the first follow up, 44 per cent of the folic acid group had adenomas versus 42 per cent in the placebo group. At the second follow up, these figures were 42 versus 37 per cent respectively.
The folic acid group also showed a trend toward more advanced and multiple adenomas. In the first follow up 11 per cent of the folic acid group had advanced adenomas compared with 9 per cent in the placebo group and in the second follow up these figures were 12 and 7 per cent respectively.
The incidence of noncolorectal cancers in the folic acid group was significantly greater than in the placebo group ((11 versus 6 per cent). This was mainly due to an increase in prostate cancer.
Cole and colleagues concluded that:
"our study indicates that folate, when administered as folic acid for up to 6 years, does not decrease the risk of adenoma formation in the large intestine among individuals with previously removed adenomas."
And in regard to increased risk they said that the evidence was unclear and called for further research. However, they went to say that:
"In view of the fortification of the US food supply with folate, and some suggestions that folate could conceivably increase the risk of neoplasia even outside the colorectum, this line of investigation should have a high priority."
In an accompanying editorial, Dr Cornelia M Ulrich and Dr John D Potter, from the Fred Hutchinson Cancer Research Center in Seattle, said that this study may be raising an issue of timing. If taken early, then perhaps folic acid prevents adenomas from forming, but if taken once they are formed, it could accelerate their development into cancer.
"The most likely explanation for the increased risk of advanced and multiple adenomas in the intervention group is that undetected early precursor lesions were present in the mucosa of these patients (who are at increased adenoma risk), and that folic acid promoted growth of these lesions," they wrote.
They said this idea was supported by experimental studies where folic acid was given after lesions were present.
However, they said this study does not say anything about whether folic acid prevents adenomas in the first place, since all the patients had already had at least one when they were enrolled. It would cost a lot of money and take a long time, to prove that folic acid prevented tumours.
"The question of efficacy of folate in cancer prevention is not resolved, and animal experiments showing chemopreventive effects of folate, as well as the strong observational epidemiological evidence, speak to the potential of folate as a chemopreventive agent, if taken early. Unfortunately, primary prevention trials that start in childhood would be lengthy, expensive, and logistically nearly impossible," said Ulrich and Potter.
This is not the first time that trials with single agents has thrown up these issues, and Ulrich and Potter draw comparisons with the problem of showing betacarotene benefits in lung cancer prevention. Lessons could be learned from chemotherapy, where multiple agents are used. They said the time has come to:
"Be as thoughtful about the need for multiagent chemoprevention, not forgetting that diet is one version of this, as about the use of multiagent chemotherapy."
The question of whether to include folic acid in bread and flour has been the subject of some controversy in the UK and Australia. Experts claim that such a move would reduce the incidence of babies born with spina bifida and other conditions. Others say that high doses of folic acid interfere with treatments for malaria, and some studies suggest it may protect against heart disease and stroke.
"Folic Acid for the Prevention of Colorectal Adenomas: A Randomized Clinical Trial."
Bernard F. Cole; John A. Baron; Robert S. Sandler; Robert W. Haile; Dennis J. Ahnen; Robert S. Bresalier; Gail McKeown-Eyssen; Robert W. Summers; Richard I. Rothstein; Carol A. Burke; Dale C. Snover; Timothy R. Church; John I. Allen; Douglas J. Robertson; Gerald J. Beck; John H. Bond; Tim Byers; Jack S. Mandel; Leila A. Mott; Loretta H. Pearson; Elizabeth L. Barry; Judy R. Rees; Norman Marcon; Fred Saibil; Per Magne Ueland; E. Robert Greenberg; for the Polyp Prevention Study Group.
JAMA 2007 297: 2351-2359
Vol. 297 No. 21, June 6, 2007
Click here for Article.
Click here for more information on colorectal cancer (American Cancer Society).
Written by: Catharine Paddock
Writer: Medical News Today
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today
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Folic_acid_study
posted by dave on 6 Jun 2007 at 9:05 amOk, First the most important question: Who funded the study? If it was a drug company, any drug company directly or indirectly, then the study is in question regardless of where it is published. Why would a drug company support a study that says, in effect, "some of our drugs are not needed?" Think about that one. Next I want to see the median age and the range of ages, not the average. Average is next to meaningless except for pure mathematics. The age range is unkiown. Third, the study indicates that all those tested had a prior condition, which would seem to indicate something other than specifically "prevention" was in the hypothesis. This study may be irrelevant for young persons wanting to assure a healthy lifestyle through diet and supplements. Fourth, does anyone take folic acid only? Most people know that supplements work together. Fifth, what if the Folic acid is not being used by the body because it is taken alone? What was the supplement amount, and how does it compare to other studies? Almost any vitamin in large amounts is toxic. What was the margin of error (statistically speaking) of the results? That tells us how likely the hypothesis is to being true beyond reasonable doubt. What about a control group who were just observed and given nothing not even a placebo? We are told very little about the medical or genetic history of these people. What about the subject's diets? Were they all identical? How many male and how many female subjects were involved and what age ranges were they from? There are just too many unanswered questions in this report for me to even consider the study as relevant to anything.
If You Had Bothered To Look
posted by jack Hardwood on 7 Jun 2007 at 10:15 amIf you had bothered to look you would have seen that the study was funded by the National Institutes of Health.
I am very upset because I took folic acid all my life and still got the said cancer. I suffered, and folic acid makers who sell them in shops made money out of me.
Age Of Study Participants
posted by Dr. Farah Sturnbrough on 7 Jun 2007 at 10:19 amThe article clearly has a link to the study. Why not click on it, Dave, and look up the answers yourself rather than blowing in the wind. Here is the median age:
Recruitment occurred between July 6, 1994, and March 20, 1998. Potential participants were identified by clinical center staff using colonoscopy and pathology reports. Those participants eligible were aged 21 to 80 years and had at least 1 of the following criteria: at least 1 histologically confirmed adenoma removed within 3 months before recruitment, at least 1 histologically confirmed adenoma removed within 16 months before recruitment and a lifetime history of 2 or more confirmed adenomas, or a histologically confirmed adenoma of at least 1 cm in diameter removed within 16 months before recruitment. We required that each participant had a complete colonoscopy, with removal of all known polyps, within 3 months of enrollment. Exclusion criteria included a history of familial polyposis syndromes, invasive large intestine cancer, malabsorption syndromes, any condition that could be worsened by supplemental aspirin or folic acid, and any condition commonly treated with aspirin, nonsteroidal anti-inflammatory drugs, or folate (eg, recurrent arthritis, atherosclerotic vascular disease, and folic acid deficiency).10 To avoid the potential for folate supplementation to mask vitamin B12 deficiency,12 we measured plasma vitamin B12 levels in all participants before randomization and excluded those with evidence of deficiency (<162 pg/mL). We also assayed methylmalonic acid in those participants whose vitamin B12 levels were marginal (162-366 pg/mL). Participants having increased methylmalonic acid (>396 nmol/L) were not randomized. Additionally, participants who required baseline methylmalonic acid testing, and who were in the highest quintile of acceptable methylmalonic acid at baseline, were retested before treatment continuation in the second follow-up interval. Women of childbearing potential had to provide agreement to use effective birth control for the duration of the study.
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