Ecological and experimental studies have suggested a relationship between Asian pickled vegetable consumption and esophageal squamous cell carcinoma.

The results of epidemiological studies investigating the association have been inconsistent.

Dr Islami and colleagues from Iran conducted a meta-analysis of observational studies of this association to evaluate the existing evidence.

The research team searched the PubMed, ISI-Web of Science, J-EAST, IndMed, Vip Chinese Periodical and China National Knowledge Infrastructure databases for all studies published in English or Chinese languages. 

Pooled results for all studies combined and for several study subgroups were computed.

The researchers included a total of 34 studies in this analysis. 

The overall random effects odds ratio and 95% confidence interval for pickled vegetable consumption was 2, but the results were heterogeneous across studies. 

After excluding the 3 most influential studies, the overall random effects odds ratio remained 2.

Similar to the overall association, the majority of subgroup analyses showed a statistically significant association between consuming pickled vegetables and oesophageal squamous cell carcinoma  risk. 

There were only three prospective studies.

Dr Islami's team concluded, "Our results suggest a potential two-fold increased risk of oesophageal cancer associated with the intake of pickled vegetables."

"However, because the majority of data was from retrospective studies and there was a high heterogeneity in the results, further well-designed prospective studies are warranted."