Relationship between financial speculation and food prices or price volatility: applying the principles of evidence-based medicine to current debates in Germany

There is an unresolved debate about the potential effects of financial speculation on food prices and price volatility. Germany's largest financial institution and leading global investment bank recently decided to continue investing in agricultural commodities, stating that there is little empirical evidence to support the notion that the growth of agricultural-based financial products has caused price increases or volatility. The statement is supported by a recently published literature review, which concludes that financial speculation does not have an adverse effect on the functioning of the agricultural commodities market. As public health professionals concerned with global food insecurity, we have appraised the methodological quality of the review using a validated and reliable appraisal tool. The appraisal revealed major shortcomings in the methodological quality of the review. These were particularly related to intransparencies in the search strategy and in the selection/presentation of studies and findings; the neglect of the possibility of publication bias; a lack of objective or rigorous criteria for assessing the scientific quality of included studies and for the formulation of conclusions. Based on the results of our appraisal, we conclude that it is not justified to reject the hypothesis that financial speculation might have adverse effects on food prices/price volatility. We hope to initiate reflections about scientific standards beyond the boundaries of disciplines and call for high quality, rigorous systematic reviews on the effects of financial speculation on food prices or price volatility.