Heavy metals, natural elements with high atomic weight and density, accumulate in biotic tissues due to anthropogenic activities. They impair vital cellular functions by binding to biomolecules. The ancients recognized the toxicity of arsenic, mercury, and lead, but systematic investigations of other heavy metals began only in the 19th century. Heavy metals cadmium, mercury, and lead, rank among the WHO’s 10 most concerning chemicals. Chelating agents mitigate heavy-metal poisoning in humans. However, dietary interventions may also be beneficial as an adjuvant strategy (along with choosing products with low heavy-metal content) to reduce the toxic effects of heavy metals ingested through food or water. Certain foods have been shown to enhance the excretion of heavy metals from the body. Other foods may protect against oxidative stress and inflammation induced by heavy metals.
Cadmium and lead are heavy metals that can be found in cacao-based foods, such as dark chocolate and cacao/cocoa nibs or powder, due to natural uptake from the soil or environmental contamination. These metals can cause health problems if consumed in high doses, such as kidney damage, neurological disorders, and cancer. The World Health Organization (WHO) has set limits for the maximum acceptable levels of cadmium and lead in food products, but some chocolate products may exceed these limits, especially those with high cacao content. Moreover, even if a product does not exceed the limits, one could still ingest too much cadmium and lead from other sources, such as water, vegetables, grains, or seafood. Therefore, consumers should be aware of the potential risks and choose products with low heavy metal content. In addition to selecting products with low cadmium and lead content, dietary modifications can serve as an effective adjuvant strategy for mitigating the potential adverse effects of heavy metal exposure from chocolate or cacao consumption. A recent study provides compelling evidence in support of this approach :
'... we recommend that people who are at risk of exposure to toxic metals ensure a sufficient intake of essential elements and vitamins and enhance their consumption of vegetables and fruit. Some edible plants, such as tomatoes (rich in iron, calcium, selenium, zinc, vitamins B and C, quercetin and naringenin), berries (rich in essential elements, vitamin C, anthocyanin and catechin), onions (rich in selenium, quercetin and vitamins B and C), garlics (rich in sulphur-containing compounds, essential elements and vitamins C and E) and grapes (rich in vitamins, essential elements and anthocyanin) are of special importance as natural antagonists to Cd and Pb toxicity and should be consumed on a regular basis. These dietary supplements are an affordable option, with fewer side effects than chelation therapy, for the billions of people around the world who are inadvertently exposed to toxic metals on a daily basis'.
- Zhai, Narbad, and Chen, “Dietary Strategies for the Treatment of Cadmium and Lead Toxicity.” https://doi.org/10.3390/nu7010552