Dark chocolate may have health benefits, but do you have to worry about lead in the bar?

Dark chocolate has long been touted as having health benefits. We’re told it can improve our moods, reduce inflammation and increase blood flow.

But some researchers are now warning that there are heavy metals in some of our favorite dark chocolate bars.

Consumer Reports tested 28 dark chocolate bars, including Dove’s, Ghirardelli’s, Lindt’s, and Hershey’s for lead and cadmium. For 23 of these bars, just one ounce of chocolate violated the California Maximum Allowable Dose Levels (MADL) for lead or cadmium, which are 0.5 micrograms and 4.1 micrograms per day, respectively.

A typical chocolate bar loosely ranges from 1.5 ounces to 3.5 ounces.

California restrictions set forth in Proposition 65 are some of the most protective in the country, according to Consumer Reports. The FDA offers more flexible recommendations for daily lead consumption at 2.2 micrograms for children and 8.8 micrograms for women of childbearing age.

As reported by Consumer Reports, an ounce of Lindt’s Excellence Dark Chocolate 70% Cocoa or Dove’s Promises Deeper Dark Chocolate 70% Cacao exceeds acceptable cadmium levels, while an ounce of Godiva’s Signature Dark Chocolate 72% Cacao or Hershey’s Special Dark Mildly Sweet Chocolate exceeds acceptable lead levels.

Trader Joe’s The Dark Chocolate Lover’s Chocolate 85% Cacao had higher levels of both lead and cadmium than the California border. Trader Joe’s did not immediately respond to a request for comment.

The National Association of Confectioners, which represents chocolate manufacturers including Hershey’s, Lindt’s and Godiva, reached a settlement in 2018 with As You Sow, a group advocating for enforcement of Proposition 65. The settlement specified concentration levels of both lead and cadmium that would require warning labels if get over it. The association confirms that the industry has adhered to the levels set by the settlement.

“The products reported in this study meet stringent quality and safety requirements, and the levels provided to us by Consumer Reports testing are well below the limits set by our settlement,” said association spokesman Christopher Gendelsberger. “Food safety and product quality remain our top priority, and we remain committed to transparency and social responsibility.”

Andrew Stolbach, a toxicologist at Johns Hopkins Medicine, told NPR that MADLs are set to be “very conservative” to account for people who are at higher risk because of their age and other medical conditions. When consuming chocolate in moderate quantities, He says lead and cadmium levels are nothing to worry about.

“The safety levels for lead and cadmium are set to be very protective, and you don’t have to worry about exceeding them by a modest amount,” he said. “If you make sure that the rest of your diet is good and has enough calcium and iron, you protect yourself further by preventing the absorption of some of the lead and cadmium in your diet.”

big Exposure to cadmium can cause lung cancer, birth defects, and other reproductive harm, while significant Lead exposure can slow growth and development in children and damage the brain and nervous system.

But Consumer Reports Tests have shown that it is also possible for dark chocolate bars to maintain lower levels of heavy metals, as five of the 28 bars contained levels of lead and cadmium that met california restrictions.

The settlement between the Confectioners’ Association and As You Sow, an organization that promotes corporate social responsibility, requires both parties to conduct a multi-year study to understand the root causes of heavy metals in chocolate and strategies for reducing these levels. The report, which discusses the results of a three-year study, was released in August.

Researchers have found that the cadmium in cocoa beans comes naturally from the soil and is transferred directly to the beans by the cocoa tree. Lead contamination occurs after harvest, when wet cocoa beans are exposed to soil and dust during the drying, fermentation, and transportation stages.

“The industry must convey to farmers the value of implementing better farming practices related to reducing moist cocoa beans’ contact with soil during fermentation and drying,” wrote Timothy Ann, co-author of the report who manages food safety at Lloyd’s Register. “Drying wet beans in direct contact with the ground, road surfaces and concrete patios should be discontinued as a farmer-controlled lead reduction activity.”

Reducing wet cocoa beans’ contact with soil and dust can reduce lead in chocolate by 10% to more than 25%, according to co-author and toxicologist Michael DiBartolomeis.

Other ways to reduce heavy metal levels include blending cocoa beans with higher cadmium content with those with lower levels, identifying areas of contamination, and conducting more aggressive testing, according to the report from As You Sow.