Folic Acid and Antioxidants Won't Prevent Cancer
The report below is based on a very limited sample -- women with heart disease symptoms -- so is of uncertain generalizability -- but it is reminiscent of an earlier Norwegian study of older heart disease sufferers which found "This trial did not find an effect of treatment with folic acid/vitamin B12 or vitamin B6 on total mortality or cardiovascular events". So far, then, the case for positive benefits of pill-popping would seem to be more faith-based than fact-based.
The report below is, however, disingenuous in saying that only one previous study showed an INCREASED risk of cancer from supplements. Note this recent expert comment about folates and bowel cancer:
"Other reasonable hypotheses about one-carbon metabolism and colorectal carcinogenesis, based on our current understanding of the biochemistry and underlying mechanisms, have also not been proven correct. In a recently published placebo-controlled randomized clinical trial among 1021 men and women with a recent history of colorectal adenoma, supplemental folic acid at 1 mg/d for up to 6 years did not reduce the incidence of subsequent colorectal adenomas and might have increased it."
WHOA! The folate that Americans get compulsorily added to their bread did no good and seems to have done harm?? And do we see a double blind controlled study contradicting epidemiological inferences?? Who would have believed it! They go on to admit that two animal studies have shown that folate INCREASES cancer. Aren't you glad that your government is dosing you up with the stuff and giving you no say in the matter?
The addition of folate to our bread is more and more looking like an iatrogenic disaster to come. I think I should note once again that a folate expert has reported that the addition of folate to bread seems to have caused an upsurge in bowel cancer among Americans -- JR.
Taking folic acid or other B vitamin supplements won't lower your risk of cancer, new research shows. However, the good news is that it won't increase your risk either, according to the study, which was published in the Nov. 5 issue of the Journal of the American Medical Association. "In women at risk of cardiovascular disease, we found that folic acid, vitamin B6 and vitamin B12 had no beneficial or harmful effects on the risk of invasive cancer or breast cancer," said study author Dr. Shumin Zhang, an associate professor of medicine at Brigham and Women's Hospital and Harvard Medical School, in Boston.
Because adequate levels of folic acid in women have been proven to prevent serious birth defects, the government has mandated that folic acid be added to cereals and breads since January 1998, according to the U.S. Centers for Disease Control and Prevention. Additionally, about one-third of U.S. adults take a daily multi-vitamin that contains folic acid, B6 and B12, according to the study. Some studies have suggested that supplements of these nutrients might be protective against cancer, though results have been inconsistent, according to background information in the study.
One study even suggested that such supplements might raise the risk of cancer.
To address these concerns, Zhang and colleagues reviewed data on 5,442 women who participated in the Women's Antioxidant and Folic Acid Cardiovascular Study. All of the women were over 42 years old, and had either preexisting cardiac disease or three or more risk factors for heart disease. The study participants were randomly assigned to receive either a supplement containing 2.5 milligrams (mg) of folic acid, 50 mg of vitamin B6 and 1 mg of vitamin B12, or a placebo. The study lasted 7.3 years, from April 1998 through July 2005.
During that time, 379 women developed invasive cancer -- 187 in the active treatment group and 192 in the placebo group. Of the women who developed cancer, 154 developed breast cancer -- 70 in the active treatment group and 84 in the placebo group. None of these differences were statistically significant.
However, when the researchers broke the data down by age, they did note what appeared to be a protective effect from the supplement treatment in women over 65. Zhang said this might be because older women generally have a higher need for these nutrients. But she also said these results should be "interpreted with caution," because the study wasn't designed to look at age differences. "It's something that needs further study," she added.
Victoria Stevens, strategic director of laboratory services for the American Cancer Society, agreed. "There was a suggestion of a protective effect in older women that I think is worth following-up," Stevens said.
The bottom line, according to Stevens, is that "supplements aren't a magic bullet" for cancer prevention. "There are really good reasons for women to take folic acid, especially if they're planning on having a baby, because there's really conclusive evidence that it can reduce birth defects. But, for the average woman in terms of cancer risk, folic acid and B vitamins don't seem to increase or reduce risk," Zhang said.
THE LIMITATIONS OF PEER REVIEW
Having myself often been peer-reviwed and been a reviewer, the finding below does not surprise me at all. One sometimes wonders if the reviewer has read the paper at all. My impression is that the main achievement of such reviews is to keep boat-rocking papers out of the journals and expectation-confirming papers in. Abstract follows:
What errors do peer reviewers detect, and does training improve their ability to detect them?
By Sara Schroter et al
Objective: To analyse data from a trial and report the frequencies with which major and minor errors are detected at a general medical journal, the types of errors missed and the impact of training on error detection.
Design: 607 peer reviewers at the BMJ were randomized to two intervention groups receiving different types of training (face-to-face training or a self-taught package) and a control group. Each reviewer was sent the same three test papers over the study period, each of which had nine major and five minor methodological errors inserted.
Main outcome measures: The quality of review, assessed using a validated instrument, and the number and type of errors detected before and after training.
Results: The number of major errors detected varied over the three papers. The interventions had small effects. At baseline (Paper 1) reviewers found an average of 2.58 of the nine major errors, with no notable difference between the groups. The mean number of errors reported was similar for the second and third papers, 2.71 and 3.0, respectively. Biased randomization was the error detected most frequently in all three papers, with over 60% of reviewers rejecting the papers identifying this error. Reviewers who did not reject the papers found fewer errors and the proportion finding biased randomization was less than 40% for each paper.
Conclusions: Editors should not assume that reviewers will detect most major errors, particularly those concerned with the context of study. Short training packages have only a slight impact on improving error detection.