Is dark chocolate safe? For the last couple of years, reports have been circulating which suggest that the mood and health benefits of high cocoa content, low sugar, organic chocolate (enjoyed in moderation of course) might be offset by heavy metal contamination, and not the musical kind.
US studies from Consumer Reports and others have found measurable levels of cadmium and lead in many popular dark chocolate bars, including a number which are sold in Australia. Consistent, long term exposure to these minerals can lead to a variety of health problems, particularly for pregnant people and young children, affecting brain development and causing developmental problems in extreme cases.
Too much lead can create nervous system problems, hypertension, immune system suppression and kidney damage. Too much cadmium can irritate the stomach, cause vomiting, dangerous bone fragility and the chances of developing cancer.
While these are real risks, the reports which caused most of the media hysteria in terms of dark chocolate were not peer-reviewed, and need to be put in context.
Where do the metals come from?
In terms of cocoa production, cadmium is something which the plants take up from the soil, while the mineral lead tends to enter the picture due to poor handling practices, post-harvest.
Because cocoa bean shells are wet and acidic after harvest, they can absorb lead from soil before and during the drying and packing stages.
Digging deeper, cadmium, lead and other heavy metals appear in a wide variety of foods, including large fish (it travels up the food chain), organ meats, rice and rice products, leafy vegetables, root vegetables, fruit juice and canned/packaged foods from places with lax food regulations.
There are various food safety standards relating to heavy metals in different places.
In California, where the chocolate studies were done, there’s a standard called MADL (Maximum Allowable Dose Level), which refers to the highest level of exposure to a chemical that is considered safe. It is deliberately conservative, and has been set at a level much lower than would be necessary to cause harm for most individuals, in order to protect the most at-risk groups.
For example, the average body weight under MADL is 65kg, although average weight in the US and Australia is now higher, and the impact of heavy metals is lesser in larger bodies. In a global context, there is no consensus about how much cadmium can be safely consumed, but all jurisdictions pitch the safe level well above MADL.
Trace minerals like zinc, magnesium, calcium and iron (found in cocoa and many other foods) also reduce the toxicity of cadmium in the body. Likewise, foods rich in calcium, iron and Vitamin C cause the body to absorb less lead from other food sources.
How much is too much?
The unfortunate fact is that these days no food is 100 per cent heavy metal free. For most people it’s impossible to avoid eating a certain amount, and our bodies can deal with it if we don’t eat too much.
It’s safer for children and other vulnerable people to not eat foods containing high levels of heavy metals on an empty stomach, because more is absorbed.
If you’re at particular risk, or are also exposed to other sources of heavy metals, then don’t eat too much dark chocolate, and don’t eat it every day. The recommended dose of about 28 grams (not every day) is safe in the view of most experts.
The secret appears to be moderation, in dark chocolate as for pretty much everything else.
