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Higher dietary folate intake reduces the breast cancer risk: a systematic review and meta-analysis.

Chen P, Li C, Li X, Li J, Chu R, Wang H - Br. J. Cancer (2014)

Bottom Line: Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg.Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake.No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.

ABSTRACT

Background: Many epidemiological studies have investigated the association between folate intake, circulating folate level and risk of breast cancer; however, the findings were inconsistent between the studies.

Methods: We searched the PubMed and MEDLINE databases updated to January, 2014 and performed the systematic review and meta-analysis of the published epidemiological studies to assess the associations between folate intake level, circulating folate level and the overall risk of breast cancer.

Results: In all, 16 eligible prospective studies with a total of 744 068 participants and 26 205 breast cancer patients and 26 case-control studies with a total of 16 826 cases and 21 820 controls that have evaluated the association between folate intake and breast cancer risk were identified. Pooled analysis of the prospective studies and case-control studies suggested a potential nonlinearity relationship for dietary folate intake and breast cancer risk. Prospective studies indicated a U-shaped relationship for the dietary folate intake and breast cancer risk. Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg. The case-control studies also suggested a significantly negative correlation between the dietary folate intake level and the breast cancer risk. Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake. No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.

Conclusions: Our studies suggested that folate may have preventive effects against breast cancer risk, especially for those with higher alcohol consumption level; however, the dose and timing are critical and more studies are warranted to further elucidate the questions.

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Related in: MedlinePlus

Forest plot of the summary OR of breast cancer for women in the highest category of dietary folate intake compared with those in the lowest category for the case–control studies.
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fig4: Forest plot of the summary OR of breast cancer for women in the highest category of dietary folate intake compared with those in the lowest category for the case–control studies.

Mentions: For the 25 case–control studies, the pooled OR was 0.79 (95% CI=0.67–0.92; Table 2) for participants with highest category of dietary folate intake compared with those of lowest category, suggesting that higher dietary folate intake may reduce breast cancer risk (Figure 4). However, Egger's test suggested that significant publication bias may exist for the studies (P=0.006). When the trim and fill method was applied for the publication bias adjustment, we found no significant association between dietary folate intake and breast cancer risk, with the pooled OR of 0.99 (95% CI=0.84–1.16) under the random-effects model (I2=86.1%, Supplementary Figure 1). There was also no significant reduction of breast cancer risk for highest category of total folate intake compared with those of lowest category (pooled OR=0.87; 95% CI=0.61–1.23; Table 2). No significant publication bias was found for the meta-analysis study of total folate intake and breast cancer risk. In the stratification studies of dietary folate intake and breast cancer risk, we found that higher dietary folate may reduce the breast cancer risk in the populations of Europe, Australia or Asia (pooled OR=0.73; 95% CI=0.58–0.93) but not in the United States (pooled OR=0.91; 95% CI=0.76–1.09). The pooled estimate from the hospital-based case–control studies suggested that subjects in the highest category of dietary folate intake showed a 33% decrease in breast cancer risk (pooled OR=0.67; 95% CI=0.54–0.85; Table 2), whereas the population-based studies did not find such an association (Table 2). After stratifying the estimate of the dietary folate intake according to the adjustment of alcohol intake, we found that the pooled OR was 0.74 (95% CI=0.60–0.92; trim and fill-adjusted pooled OR=0.97, 95% CI=0.79–1.17) for those studies without alcohol adjustment. The pooled OR was 0.84 (95% CI=0.66–1.06) for those studies with alcohol intake adjustment (Table 2). Pooled estimate for the studies with higher-quality studies suggested that higher folate intake may reduce the breast cancer risk, but not for the studies with lower quality (Table 2).


Higher dietary folate intake reduces the breast cancer risk: a systematic review and meta-analysis.

Chen P, Li C, Li X, Li J, Chu R, Wang H - Br. J. Cancer (2014)

Forest plot of the summary OR of breast cancer for women in the highest category of dietary folate intake compared with those in the lowest category for the case–control studies.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4007237&req=5

fig4: Forest plot of the summary OR of breast cancer for women in the highest category of dietary folate intake compared with those in the lowest category for the case–control studies.
Mentions: For the 25 case–control studies, the pooled OR was 0.79 (95% CI=0.67–0.92; Table 2) for participants with highest category of dietary folate intake compared with those of lowest category, suggesting that higher dietary folate intake may reduce breast cancer risk (Figure 4). However, Egger's test suggested that significant publication bias may exist for the studies (P=0.006). When the trim and fill method was applied for the publication bias adjustment, we found no significant association between dietary folate intake and breast cancer risk, with the pooled OR of 0.99 (95% CI=0.84–1.16) under the random-effects model (I2=86.1%, Supplementary Figure 1). There was also no significant reduction of breast cancer risk for highest category of total folate intake compared with those of lowest category (pooled OR=0.87; 95% CI=0.61–1.23; Table 2). No significant publication bias was found for the meta-analysis study of total folate intake and breast cancer risk. In the stratification studies of dietary folate intake and breast cancer risk, we found that higher dietary folate may reduce the breast cancer risk in the populations of Europe, Australia or Asia (pooled OR=0.73; 95% CI=0.58–0.93) but not in the United States (pooled OR=0.91; 95% CI=0.76–1.09). The pooled estimate from the hospital-based case–control studies suggested that subjects in the highest category of dietary folate intake showed a 33% decrease in breast cancer risk (pooled OR=0.67; 95% CI=0.54–0.85; Table 2), whereas the population-based studies did not find such an association (Table 2). After stratifying the estimate of the dietary folate intake according to the adjustment of alcohol intake, we found that the pooled OR was 0.74 (95% CI=0.60–0.92; trim and fill-adjusted pooled OR=0.97, 95% CI=0.79–1.17) for those studies without alcohol adjustment. The pooled OR was 0.84 (95% CI=0.66–1.06) for those studies with alcohol intake adjustment (Table 2). Pooled estimate for the studies with higher-quality studies suggested that higher folate intake may reduce the breast cancer risk, but not for the studies with lower quality (Table 2).

Bottom Line: Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg.Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake.No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.

ABSTRACT

Background: Many epidemiological studies have investigated the association between folate intake, circulating folate level and risk of breast cancer; however, the findings were inconsistent between the studies.

Methods: We searched the PubMed and MEDLINE databases updated to January, 2014 and performed the systematic review and meta-analysis of the published epidemiological studies to assess the associations between folate intake level, circulating folate level and the overall risk of breast cancer.

Results: In all, 16 eligible prospective studies with a total of 744 068 participants and 26 205 breast cancer patients and 26 case-control studies with a total of 16 826 cases and 21 820 controls that have evaluated the association between folate intake and breast cancer risk were identified. Pooled analysis of the prospective studies and case-control studies suggested a potential nonlinearity relationship for dietary folate intake and breast cancer risk. Prospective studies indicated a U-shaped relationship for the dietary folate intake and breast cancer risk. Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg. The case-control studies also suggested a significantly negative correlation between the dietary folate intake level and the breast cancer risk. Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake. No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.

Conclusions: Our studies suggested that folate may have preventive effects against breast cancer risk, especially for those with higher alcohol consumption level; however, the dose and timing are critical and more studies are warranted to further elucidate the questions.

Show MeSH
Related in: MedlinePlus