Elsevier

Nutrition

Volume 31, Issue 1, January 2015, Pages 45-50
Nutrition

Meta-analysis
Association between processed meat and red meat consumption and risk for glioma: A meta-analysis from 14 articles

https://doi.org/10.1016/j.nut.2014.04.022Get rights and content

Abstract

Objective

Epidemiologic studies evaluating the association between processed meat and red meat consumption and glioma risk have produced inconsistent results. Thus, the aim of this study was to conduct a meta-analysis to test the hypothesis that high levels of processed meat consumption could increase the risk for glioma.

Methods

Pertinent studies were identified by a search of PubMed and Web of Knowledge up to February 2014. Random-effects model was used to combine the results. Publication bias was estimated using Egger's regression asymmetry test.

Results

Fourteen studies involving 3641 cases about processed meat consumption and 3 studies involving 1156 cases about red meat consumption with risk for glioma were included in this meta-analysis. The combined relative risk (RR) of glioma associated with processed meat consumption was 1.25 (95% confidence interval [CI], 1.08–1.45) overall, and 1.28 (95% CI, 1.09–1.50) in the United States. For subgroup of study design, significant association was also found in case–control studies (RR, 1.33; 95% CI, 1.09–1.62), but not in the cohort studies. The association was not significant between red meat consumption and glioma risk (summary RR, 0.89; 95% CI, 0.71–1.12). No publication biases were found.

Conclusions

Our analysis indicated that high levels of processed meat consumption might increase the risk for glioma, and findings are consistent with the hypothesis. No association was found between red meat consumption and glioma risk.

Introduction

Glioma is the most common primary brain tumor that occurs most frequently in adults, accounting for ∼70% of adult brain malignancies [1], [2]. Glioma has an incidence of 5 to 10 cases per 100 000 [1]. It has been suggested that genetic predisposition and ionizing radiation are risk factors for brain tumors [3], [4]. 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]. N-nitroso compounds are broadly acting and potent carcinogens in animal models [5]. Food items that usually include N-nitroso compounds are namely, processed meats, such as ham, hot dogs, salami, bacon, and lunchmeat.

Meat is a major source of protein and fat for humans. An association has been suggested between consumption of meat, in particular processed meat, and an increased risk for some diseases, including cancers [6], [7], stroke [8], type 2 diabetes [9], and cardiovascular disease [10]. Processed meats are usually preserved with nitrite and also may contain N-nitroso compounds. N-nitroso compounds can further be formed endogenously in the stomach from nitrites and ingested amides in foods of animal origin [11]. The hypothesis that N-nitroso compounds may be involved in the etiology of brain tumors comes both from observations in animal studies that these compounds may be able to pass through the blood–brain barrier, and that such compounds may be highly carcinogenic in animals [12]. In this meta-analysis, we sought to provide evidence consistent with this hypothesis that high levels of processed meat consumption could increase the risk for glioma.

Section snippets

Search strategy

A comprehensive search was conducted for available articles published in English using the databases of PubMed and Web of Knowledge up to February 2014. The following search terms were used: glioma or cancer or brain cancer AND red meat (unprocessed) or cured meat or processed meat or diet or lifestyle or food. We also searched for relevant papers in the reference list of reviews, commentaries, or original papers through the string N-nitroso brain cancer hypothesis [13], [14], [15] by hand

Search results and study characteristics

We identified 14 articles [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34] that were eligible for inclusion in the meta-analysis. Among these articles, 10 were carried out in the United States, 2 in Europe, 1 in Australia, and 1 in Israel. Sample sizes ranged from 48 to 3671 for case–control studies and 34 000 to 545 770 for cohort studies. Combined, these studies involved 3896 glioma cases and 877 640 participants. Characteristics of these studies are

Discussion

Findings from this meta-analysis suggested that the intake of processed meat might increase the risk for glioma. Most of the data on the issue come from the United States; thus it is obvious that the RR estimate for the United States reflects that for overall studies combined. We cannot combine the results for Europe, Australia, and Israel because of limited data. Furthermore, only three studies were conducted for red meat, and no association was found between red meat consumption and glioma

Conclusion

Results from this meta-analysis, including data mostly from the United States, suggest that processed meat consumption might increase the risk for glioma. Our findings are consistent with the hypothesis. No association was found between red meat consumption and glioma risk.

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    YDW conceived of the study and drafted the manuscript. YDW, DZZ, and DC carried out the literature search and data extraction. PX analyzed the data.

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