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Folic Acid, Vitamin B12 Linked to Cancer
Reported December 25, 2009
(Ivanhoe Newswire) -- Patients with heart disease in Norway, a
country where foods are not fortified with folic acid, had an increased risk
of cancer and death from any cause if they received treatment with folic
acid and vitamin B12.
Most epidemiological studies have found inverse associations between intake
of folate, a B vitamin, and risk of colorectal cancer. Similar associations
have been inconsistent or absent for other cancers, however.
Marta Ebbing, M.D., of Haukeland University Hospital, Bergen, Norway, and
colleagues analyzed the results of two Norwegian trials among patients with
ischemic heart disease, where there was a statistically insignificant
increase in cancer incidence in the groups assigned to folic acid treatment.
The researchers examined whether folic acid treatment was associated with
cancer outcomes and all-cause mortality after extended follow-up. The
authors were quoted as saying, "Because there is no folic acid fortification
of foods in Norway, this study population was well suited for such an
investigation."
"Experimental evidence suggests that folate deficiency may promote initial
stages of carcinogenesis, whereas high doses of folic acid may enhance
growth of cancer cells,” the authors wrote. “Since 1998, many countries,
including the United States, have implemented mandatory folic acid
fortification of flour and grain products to reduce the risk of neural-tube
birth defects. Recently, concerns have emerged about the safety of folic
acid, in particular with respect to cancer risk."
The two clinical trials included 6,837 patients with ischemic heart disease
who were treated with B vitamins or placebo between 1998 and 2005, and were
followed up through the end of 2007.
The researchers found that after a median 39 months of treatment and an
additional 38 months of post-trial follow-up, 288 participants who did not
receive folic acid plus vitamin B12 versus 341 participants who received
such treatment were diagnosed with cancer, representing a 21 percent
increased risk.
A total of 100 patients who did not receive folic acid plus vitamin B12
versus 136 who received such treatment died from cancer, a 38 percent
increased risk. A total of 16.1 percent of patients who received folic acid
plus vitamin B12 vs. 13.8 percent who did not receive such treatment died
from any cause.
"Results were mainly driven by increased lung cancer incidence in
participants who received folic acid plus vitamin B12. Vitamin B6 treatment
was not associated with any significant effects," the authors wrote. "Our
results need confirmation in other populations and underline the call for
safety monitoring following the widespread consumption of folic acid from
dietary supplements and fortified foods."
SOURCE: Journal of the American Medical Association (JAMA), November 18,
2009 |
