Dark chocolate has long been touted as a healthier option for people looking to satisfy their sweet tooth without raising their blood sugar.
But what millions of people may not know is that they can also contain heavy metals linked to cancer.
Multiple tests by consumer watchdogs have found high levels of cadmium and lead in chocolate products, which have been associated with kidney and bone disease, brain damage, miscarriages and tumor growth.
Now Brian Johnson, a 46-year-old biohacker who claims to have reversed his biological age by a decade, has analyzed 10 popular dark chocolate bars to find the worst offenders.
All 10 dark chocolate bars contained detectable metals (although Johnson does not specify which metals he tested) and two products made by Alter Eco received the worst scores because they had triple the levels of some rival brands.
The scale ranged from zero to 100, with higher scores indicating better products.
In addition to metal levels, Johnson also looked at flavanols, plant compounds that can improve heart and brain health, help fight cell damage and infections, and protect the body from toxins and inflammation.
Based on the amount of flavanols and heavy metals each chocolate bar had, the biohacker, who spends $2 million a year on his anti-aging lifestyle, assigned a score to each product.
The scale ranged from zero to 100, with lower scores indicating a worse health profile.
Johnson tested 10 popular dark chocolate bars, including Lindt Excellence, Ritter Sport, Beyond Good, Alter Eco, Hu and Tony’s Chocolonely.
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They ranged from 70 percent cocoa to 100 percent cocoa, with some claiming to be sustainably sourced, good for the environment and free of processed additives.
Of the 10 products, Alter Eco’s Classic Opaque Dark Chocolate with 85 Percent Cocoa scored the lowest, 13.
While it had higher levels of flavanols (140.5 mg), it contained 10.6 micrograms of heavy metals.
A second Alter Eco product earned a similar score: 100 percent total cocoa blackout chocolate, with 210.5 mg of flavanols and 14.7 mcg of heavy metals, giving it a score of 14.
Brian Johnson is a biohacker who claims to have reverted his biological age from 46 to 37 years old
The highest-scoring product Johnson tested was the Vosges Black Salt Caramel 72 Percent Cocoa Exotic Chocolate Bar, which had 159 mg of flavanols and only 2.0 mcg of heavy metals, giving it a score of 78.
Johnson said: ‘What we have learned today is several things. One: marketing and packaging mean nothing. It doesn’t matter what they say. It doesn’t matter what words they use, or how pretty their images are. It doesn’t matter.
‘Second: Not knowing is very dangerous… That is why it is so important to know what you eat and have quantified data about cleanliness and positive benefits.
‘Transparency in our food supply chain is a good thing for everyone. No one wins when our food supply is dirty. Nobody wins when we are not healthy. It is time for us to change the world from a “dying economy” to a “non-dying economy.”
There is no nationally established federal level for exposure to lead and cadmium, but 2017 investigation determined that 62 micrograms (mcg) of cadmium is the highest tolerable level for a 154-pound person per day when it comes to kidney health.
While the FDA lists the tolerability level for cadmium as between 0.21 and 0.36 micrograms of cadmium per day per approximately 2 pounds of body weight, or approximately 25 micrograms for a 154-pound person.
There is no safe level of lead exposure, but the FDA’s acceptable daily intake of lead in food is 2.2 micrograms for children and approximately 8.8 micrograms for adults.
California has even stricter safe level recommendations: no more than 0.5 mcg of lead per day and no more than 4.1 mcg of cadmium.
Chocolate can be exposed to heavy metals through cocoa powder, which is used to give the bars their velvety chocolate flavor.
Lead can mix with cocoa when the beans are left to dry on the side of roads and then covered in car fumes.
Cadmium may be inside the beans when they are picked, because the cocoa tree may have extracted it from the ground.
A Tony Chocolonely product scored 37 out of 100
Separate research published in July by George Washington University analyzed 72 commercial cocoa products over eight years, analyzing them for heavy metals such as lead, cadmium and arsenic.
Researchers found that all of the products contained traces of toxic metals and nearly half had up to 20 percent more than the maximum allowable dose of lead.
More than a third exceeded permitted levels of cadmium, which has been linked to cancer and kidney damage.
The researchers did not reveal which chocolates were tested.
And a 2023 investigation found that 16 of 48 chocolates tested (one-third) had high levels of lead or cadmium, and each contained detectable levels of those metals.
This included Hershey’s milk chocolate bars and hot chocolate mixes from Trader Joe’s, Starbucks and Ghirardelli.
