Elsevier

Nutrition

Volume 30, Issues 11–12, November–December 2014, Pages 1272-1278
Nutrition

Meta-analysis
Association between fruit and vegetable intake and risk for glioma: A meta-analysis

https://doi.org/10.1016/j.nut.2014.03.027Get rights and content

Abstract

Objective

Epidemiologic studies evaluating the association between the intake of vegetables and fruit and the risk for glioma have produced inconsistent results. Therefore, the aim of this study was to test the hypothesis that higher vegetable and fruit intake may have a protective effect on risk for glioma.

Methods

Pertinent studies were identified by a search in PubMed, Web of Knowledge, and Wan Fang Med Online up to January 2014. Random-effect model was used to combine study-specific results. Publication bias was estimated using Begg's funnel plot and Egger's regression asymmetry test.

Results

Fifteen studies involving 5562 cases focusing on vegetable intake and 17 studies involving 3994 cases of fruit intake compared with the risk for glioma were included in this meta-analysis. The combined relative risk (RR) of glioma associated with vegetable intake was 0.775 (95% confidence interval [CI], 0.688–0.872) overall, and the association for subgroup analysis by study design, sources of control, ethnicity, and number of cases was consistent with overall data. For fruit intake and glioma risk, significant protective associations were found in an Asian population (RR, 0.573; 95% CI, 0.346–0.947), but not in a white population. No publication bias was found.

Conclusions

This analysis indicated that intake of vegetables might have a protective effect on glioma. The intake of fruit might have a protective effect on glioma in the Asian population; however, the results need to be confirmed.

Introduction

Glioma is the most common primary brain tumor, occurring most frequently in adults and accounting for approximately 70% of adult brain malignancies [1], [2]. It has an incidence of 5 to 10 cases per 100 000 [1]. Evidence has suggested that a genetic predisposition and ionizing radiation are established risk factors for brain tumors [3], [4], [5]. Additionally, other potential risk factors include exposure to environmental chemical carcinogens, such as chemical agents and, among dietary factors, exposure to N-nitroso compounds [1], [3]. Due to the highly invasive character of glioma, complete resection is difficult to achieve [6]. Thus, prevention of glioma progression has become an important strategy for fighting the disease [7].

The intake of fruit and vegetables has long been associated with a decreased risk for various diseases [8], [9]. The suggested mechanisms for the major role of vegetables and fruit include modulation of DNA methylation; protection from and repair of DNA damage; promotion of apoptosis; and induction of detoxifying phase II enzymes [10]. To date, a number of epidemiologic studies have explored the relationship between fruit and vegetable intake and the risk for glioma. However, results are not consistent [11], [12], [13], [14]. Thus, to better characterize this issue, we conducted a comprehensive meta-analysis to evaluate the evidence from observational studies on the association between vegetable and fruit intake and the risk for glioma by summarizing it quantitatively with a meta-analysis approach.

Section snippets

Search strategy

A comprehensive search was conducted for available articles published in English or Chinese using the databases of PubMed, Web of Knowledge, and Wan Fang Med Online up to January 2014 and by hand-searching the reference lists of the computer-retrieved articles. The following search terms were used: glioma AND (neoplasm OR carcinoma OR cancer) combined with nutrition OR diet OR lifestyle OR fruit OR vegetable. Two investigators searched articles and reviewed all retrieved studies independently.

Search results and study characteristics

The search strategy identified 312 articles from PubMed, 11 from Wan Fang Med Online, and 432 from the Web of Knowledge. Twenty-nine articles were reviewed in full after reading the title/abstract. By studying reference lists, we identified two additional articles. Sixteen of these 31 articles were subsequently excluded from the meta-analysis for various reasons. Hence, 12 articles [12], [13], [14], [22], [23], [24], [25], [26], [27], [28], [29], [30] with 15 studies (1 prospective study and 14

Discussion

Findings from this meta-analysis suggested that the intake of vegetables might have a protective effect on glioma (pooled RR, 0.775; 95% CI, 0.688–0.872) for overall data and all subgroup analyses. The intake of fruit might have a protective effect on glioma only in an Asian population (RR, 0.573; 95% CI, 0.346–0.947) and hospital-based case–control studies (RR, 0.586; 95% CI, 0.398–0.863), but not in other subgroups.

Previous meta-analyses have suggested that a favorable effect was found

Conclusion

In summary, results from this meta-analysis suggested that the intake of vegetables might have a protective effect on glioma. The intake of fruit may have a protective effect on glioma in an Asian population, which needs to be confirmed.

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