MONDAY, Nov. 27 (HealthDay News) -- Women with a low dietary intake of folate do not have an increased risk of breast cancer compared to those with higher intakes, according to study findings published in the Nov. 15 issue of the Journal of the National Cancer Institute.
Sarah J. Lewis, Ph.D., of the University of Bristol in the United Kingdom, and colleagues conducted a meta-analysis of 13 case-control studies and nine cohort studies.
In the case-control studies, the researchers found that every 100-microgram/day increase in folate intake was associated with a 9 percent reduction in breast cancer risk. But they cautioned that these studies may have suffered from publication bias, dietary assessment measurement errors, confounding by factors associated with dietary intake, or recall bias. In the nine cohort studies, they found no association between folate intake and breast cancer risk. A separate meta-analysis found no difference in breast cancer risk between those homozygous for the TT version of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene and CC homozygotes, and no evidence of an interaction between folate intake and MTHFR genotype on breast cancer risk.
"Judging from the study design (i.e., observational studies), inconsistent results from case-control and cohort studies, publication bias, and sparse data, the strength of evidence on the association between folate intake and breast cancer risk is very low, suggesting that any estimate of effect is very uncertain," states the author of an accompanying editorial.
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