A study by Consumer Reports has found dangerously high levels of heavy metals in chocolate from well-known brands including Hershey’s, Theo, and Trader Joe’s.

Of particular concern are levels in dark chocolate, which many people have come to believe is better for you than milk chocolate, according to the watchdog organization. Scientists recently measured various heavy metals in 28 dark chocolate bars and found cadmium and lead in all of them.

In addition to major brands including Dove and Ghirardelli, Consumer Reports tested lesser-known brands including Alter Eco and Mast.

For 23 of the 28 bars tested, eating one ounce a day would put an adult over the level of one of the heavy metals that health authorities say is safe for adults. Five of the brands had higher levels of both metals. Acceptable levels for children are much lower.

It has long been known that heavy metals, particularly lead, can cause serious health problems for all people, but especially for children who are at risk for developmental problems, impaired brain development, lower IQ scores, and other issues. It is for these reasons that lead has long been banned from paint and plumbing.

“But there are risks for people of any age, said Tunde Akinleye, the Consumer Reports food safety researcher who led the testing project.

“Frequent exposure to lead in adults, for example, can lead to nervous system problems, hypertension, immune system suppression, kidney damage, and reproductive issues”

While most people don’t eat chocolate every day, 15 percent do, according to Mintel, a market research firm. When combined with levels of lead and cadmium in other foods the problems can add up. For example, heavy metals can be found in carrots, sweet potatoes, and spinach, which are all considered to be healthy foods.

Balancing act
While dark chocolate is lauded for many reasons such as lower sugar and higher fiber than milk chocolate, the very things that make it “better” can cause problems. The cacao, or cocoa, levels in dark chocolate are proclaimed on packaging as signals about which brands or sub-brands are more healthy, with higher percentages translating into more so-called health benefits.

The problem is that the “cocoa solids are also wher the heavy metals, especially cadmium lurk,” according to the Consumer Reports research team.

“Some of the same concerns may extend to products made with cocoa powder — which is pure cocoa solids — such as hot cocoa and brownie and cake mixes.”

But there is hope
Researchers have found that cacao plants take up cadmium from the soil, so growing the plants in soil with lower cadmium density makes a difference. However, lead seems to get into the cacao beans after harvest, so different mitigation methods are needed.

The researchers found that lead was typically on the outer shell of the cocoa bean, not in the bean itself.

“Moreover, lead levels were low soon after beans were picked and removed from pods but increased as beans dried in the sun for days. During that time, lead-filled dust and dirt accumulated on the beans,” researchers said.

To mitigate lead contamination, changes in harvesting and manufacturing practices are needed, according to Danielle Fugere, president of As You Sow, which is an organization that pushes for corporate accountability. Such practices will include minimizing the amount of soil contact for the beans and finding ways to remove lead when beans are cleaned at factories.

Mitigation of cadmium is not so easy, according to the researchers. Careful breeding to create plants that do not take up as much of the substance during growth is one option. That will take time. Another option would be to replac older trees with younger ones, but that will also take time and financial investment.

Careful decisions about wher to grow cocoa plants should also be implemented to avoid places wher the soil is more heavily contaminated with lead and cadmium.

The National Confectioners Association funded the chocolate research as part of a settlement with As You Sow.