Exposures and risks of arsenic, cadmium, lead, and mercury in cocoa beans and cocoa-based foods: a systematic review

Background: The World Health Organization has expressed concern about arsenic, cadmium, lead, and mercury as potentially harmful to human health. As such, the world body has called for appropriate preventive and interventionary measures. In response, food regulatory bodies including European Food Safety Authority are monitoring the levels of these heavy metals in cocoa and cocoa products. Objective: Therefore, the objective of this paper is to synthesize the latest relevant available peer-reviewed publications on arsenic, cadmium, lead, and mercury with a view to highlighting the gaps to encourage further research and informing industry. Materials and Methods: A systematic review was conducted using the European Food Safety Authority guide in PubMed database and the result was reported according to the PRISMA checklist. Results: The results show that processing may dilute or concentrate the levels of arsenic, cadmium, lead, and mercury, depending on processing factors including the product type, processing method, and raw materials. In addition, some products exceed the European Union and Chinese Maximum Contaminant Level and may pose risk. Furthermore, the findings show that the risk of heavy metal toxicities was higher among children relative to adults at the same exposure in cocoa-based products and that correcting risk estimates for bioavailability reduces the level of estimated risk. Conclusion: Therefore, the review concludes that further research is required to clarify the effect of processing on the level of these contaminants in specific cocoa-based foods. Moreover, conducting risk studies based on age groups and correcting for bioavailability of arsenic, cadmium, lead, and mercury enhance accuracy of risk estimates. Recommendations: The review, therefore, recommends that a value chain approach be adopted to assessing the levels, exposures, and risks of arsenic, cadmium, lead, and mercury in cocoa-based foods and the effect of processing on these levels.