Research Highlights: How does heavy metal cadmium get into your chocolate?

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How does heavy metal cadmium get into your chocolate?

  • Cocoa is a chocolate powder made from ground cacao seeds.
  • Cacao seeds naturally contain cadmium originating from the soil because of volcanic activities, eroded rocks, and forest fires.[2]
  • Cadmium is a soft, silvery-white metal and is similar in many respects to zinc.
  • Cadmium can cause damage to the kidney especially to the proximal tubular cells.[1]
  • Cadmium can also cause bone demineralization through direct bone damage or as a result of renal dysfunction.[1]
  • Abnormal high concentration of cadmium in cacao and other cocoa-based products such as chocolate may cause serious human health issues.
  • Current regulations established a threshold for cadmium content of cocoa-based products.
  • However, the biophysical factors such as climate and soil conditions that determine the concentration of soil-derived cadmium in the cacao seed are not well understood.
  • Researchers used scientific literature to compile a database from across the Cacao Belt to determine the primary drivers of cacao seed cadmium.
  • Cacao Belt refers to the regions approximately 20 degrees latitude on either side of the equator.
  • Researchers discovered that total soil cadmium and soil pH can significantly affect the concentration of cadmium in cacao seeds.
  • Both available soil cadmium and soil organic carbon content do not influence cacao seed cadmium concentration.
  • Soil pH and soil organic carbon decreased the degree of bioconcentration of total soil cadmium in the cacao seed cadmium concentration.
  • The results suggest that cadmium reduction strategies utilizing plant physiology-based approach are better compared to soil-based approaches.
  • If using soil-based approaches, researchers suggest to use strategies that can increase soil pH greater than 6.0.


Wade J, Ac-Pangan M, Favoretto VR, Taylor AJ, Engeseth N, Margenot AJ (2022) Drivers of cadmium accumulation in Theobroma cacao L. beans: A quantitative synthesis of soil-plant relationships across the Cacao Belt. PLoS ONE 17(2): e0261989.



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