Despite spooky Consumer Reports’ testing, metals in chocolates aren’t scary

With Halloween bounties now collected and as end-of-year holidays that brim with tempting treats approach, you may once again be wondering about the dangers of indulging. Among the most alarming concerns to gain attention recently is the risk of heavy metals in candy. Last week, Consumer Reports (CR) released its second article highlighting that one of America's most beloved confections—chocolates—can contain small amounts of the toxic metals lead and cadmium.

CR tested 48 chocolate products in various categories—from milk chocolate bars to brownie mixes, chocolate chips, and hot chocolate—finding "high" and "concerning" levels of at least one of the two heavy metals in a third of the products. Last year, the nonprofit consumer organization tested 28 bars of dark chocolate, finding what it suggested was "dangerous" levels of cadmium and/or lead in 23 of the bars.

The news made waves last year and may renew fears about what's lurking in holiday treats. But, a closer look at the data—as well as reactions from actual medical toxicologists—indicates that the risk of heavy metals in chocolate is actually pretty low.

CR used a very conservative threshold for determining "high" levels of the metals, which are not backed by major regulatory and health agencies, including the World Health Organization and the Food and Drug Administration. While pressuring chocolate companies to do more to keep contaminants out of our treats is a reasonable goal, this is not something anyone needs to fret about.

The threshold CR used: California’s MADLs

CR told Ars it would not release its raw chocolate data to us, telling us it was proprietary. But, according to the report article, it based its threshold for levels of cadmium and lead in chocolate products on the MADLs set by California's Proposition 65, the state's initiative to reduce exposures to toxic chemicals. Generally, Prop 65 MADLs, or the "Maximum Allowable Dose Levels," are calculated by looking at the most sensitive toxicology studies on a potentially harmful substance, determining the level of exposure at which there is no detectable harm—aka the NOEL for "No Observable Effect Level"—and then dividing the NOEL by 1,000.

Thus, a MADL is one-thousandth the level at which there is no observable harm, which, as the state of California puts it, is "to provide an ample margin of safety."

"MADLs are set to be very conservative," Dr. Andrew Stolbach, a medical toxicologist and emergency physician at Johns Hopkins Medicine, told Ars over email. "There are extra safety factors built in to account for people much more at risk (by virtue of age, intake levels, or other medical conditions)."

The MADL for cadmium is 4.1 micrograms per day (µg/day). For lead, the MADL is 0.5 µg/day.

If a sample of a chocolate product was above these levels, CR considered it high and, in some cases, "concerning." The organization didn't report the raw numbers for samples—which were also averages of three samples from the same lot—it only reported percentages. For instance, Target's "Good & Gather Semi-Sweet Mini Chocolate Chips" reportedly had 102 percent of the MADL for lead—which works out to 0.51 µg per serving. Based on that, it was therefore considered "high." Some other samples had levels that were double or triple the MADLs.

It's important to note, however, that these MADLs are not currently enforced in California. Chocolate makers and As You Sow, a nonprofit that advocates for corporate responsibility, entered into a consent judgment in 2018, which set more permissive interim limits for cadmium and lead in chocolate products as the groups work together on ways to reduce contaminant levels during production.

Additionally, the MADL levels are significantly more conservative than recommendations from the FDA and WHO.

Lead levels

From the settlement with As You Sow, California's interim limits for cadmium and lead in chocolate are by weight and vary based on the cacao content, and they blow past the Prop 65 MADLs. For instance, for lead, the interim limits for dark chocolates between 65 percent and 95 percent cacao are 0.150 parts per million (ppm), which is equivalent to 150 µg/kg. Assuming a serving is one solid ounce of chocolate, that's 4.25 µg per serving, which is 8.5 times the Prop 65 MADL. For sweeter chocolates under 65 percent cacao, the interim limit is 0.100 ppm (100 µg/kg), which works out to 2.83 µg per ounce or 5.66 times the Prop 65 MADL.

That might sound alarming until you notice that 0.100 ppm (aka 100 µg/kg) is the limit the FDA recommends for chocolates aimed at children, which are typically milk chocolate that have less cacao content. And the FDA's current recommendation for daily lead limit for children is 2.2 µg per day (4.4 times the MADL) and 8.8 µg for women of childbearing age. In a 2018 FDA study surveying cadmium and lead in 144 chocolate products sold in the US, the regulator's scientists found that the highest lead level detected in a dark chocolate was 110 µg/kg, or 3 µg per ounce. The mean was 30 µg/kg, or 0.85 µg per ounce. For milk chocolate, more popular with little ones, the mean was 10 µg/kg, or 0.28 µg per ounce.

The Joint Expert Committee on Food Additives (JECFA)—an international scientific expert committee run by the Food and Agriculture Organization of the United Nations (FAO) and the WHO—has also weighed in on lead and cadmium levels in foods. For lead, a potent neurotoxic metal that particularly affects the development of children, JECFA most recently concluded that it was not possible to determine the health-protective limit. No level of lead is safe, per se. However, it deemed amounts below 0.3 µg/kg of body weight per day to be a "negligible" risk for children. For a child weighing 20 kg, or about 44 pounds, that would set a threshold of 6 µg per day. For adults, 1.2 µg/kg of body weight per day would pose a "negligible" risk, which would set a limit for a 70 kg (155 pounds) adult to 84 µg per day.

Cadmium levels

While the Prop 65 MADL for cadmium is 4.1 µg/day, California's interim cadmium levels, like those for lead, are based on a chocolate product's weight and cacao content. For dark chocolates between 65 percent and 95 percent cacao, the interim level is set at 0.450 ppm or 450 µg/kg. For a serving of one solid ounce of chocolate, that would be 12.7 µg per ounce or 3.1 times the MADL.

The international JECFA sets a more complicated limit that accounts for the cumulative and long-term nature of cadmium exposures—which can linger in the body for years to decades. The JECFA set a tolerable monthly limit based on weight: 25 μg/kg of body weight for a month. For a 70 kg person (155 pounds), that would be 1,750 μg per month, or about 58 μg per day, assuming a 30-day month. That is roughly 14 times the Prop 65 MADL. For a 20 kg child (44 pounds), the limit would be 480 μg per month, or about 16 μg per day, about four times the Prop 65 MADL.

Of course, chocolate products are not the only source of cadmium in people's diets, which is also the case for lead. These are naturally occurring metals that make their way into foods from everything from plant-uptake from soil to human-based contamination during production. So, in its most recent review of cadmium exposures, JECFA looked at how big a role chocolate products play in exposing us to cadmium. Overall, from all foods and diets across the world, mean monthly cadmium levels from dietary exposure ranged from 0.6 μg/kg bw per month for adults in the Sikasso region of Mali (or 2.4 percent of JECFA's limit) up to 24 μg/kg bw per month in children ages 4–11 years in China (96 percent of the limit). The percentage of those exposures that come just from chocolate products ranged from 0.2 percent to 9 percent. Even when the committee combined the highest estimates of chocolate-based cadmium exposures to average exposures from people's total diets, the total cadmium exposures for both children and adults fell under JECFA's limits. And these estimates are considered overestimates.

"The contribution of cocoa products to dietary cadmium exposure was minor… even in countries in which the consumption of cocoa products is relatively high," the committee concluded.

The main sources of cadmium in people's diets worldwide are still considered to be cereals and cereal-based products, vegetables, and fish and seafood.

Medical toxicologists’ takeaways

As for the levels of cadmium and lead reported by CR: "I wouldn't expect any adverse health effects at these intake levels," Stolbach, of Johns Hopkins Medicine, told Ars.

Dr. Maryann Amirshahi, professor of emergency medicine at Georgetown University School of Medicine and co-medical director of the National Capital Poison Center, agreed. "When you factor in the margin of safety that is used in the MADL calculations and consider how much an individual consumes, it is hard to say that any one of these products is plain unsafe. A single serving of any of these products would be very unlikely to cause adverse health effects."

Absorption and other factors

Beyond the varying thresholds for safe limits, there are many other factors to consider in terms of your personal risk. As mentioned above, many other foods we eat can have small amounts of heavy metals, including lead and cadmium. So, however strict you are with chocolates, it is not going to eliminate exposures.

Your overall health, diet, genetics, and the type of heavy metal compounds you're exposed to can influence how you are affected by the exposures. As Dr. Stolbach explains: "Lead and cadmium are handled slightly differently by the body, but they are not completely absorbed, so much of what you take passes through you after you consume it. In both cases, lack of another key mineral predisposes to increased absorption. Decreased iron intake increased cadmium absorption and decreased calcium intake increases lead absorption."

For cadmium, JECFA noted that "most ingested cadmium passes through the gastrointestinal tract largely without being absorbed." In lab animals, only 0.5 percent to 3 percent of ingested cadmium becomes bioavailable on average. In humans, the cadmium that is taken up by the body largely concentrates in the kidney, liver, and placenta, with kidney dysfunction being the earliest sign of toxicity.

Cadmium has similar chemical composition to essential metals like calcium, iron, and zinc. Cadmium can bind to the same proteins in blood and tissue as zinc, as noted in a 2020 article by FDA scientists. And iron deficiency is linked to upregulation of genes that code for metal transporters in the body, which may explain why researchers have noted high levels of cadmium excretion in women with low iron stores.

For lead, uptake is dependent on factors including age, fasting, calcium and iron status, pregnancy, and the physiochemical characteristics of the ingested material, JECFA notes.

Reducing chocolate contaminants

While a deeper look into the data may put you more at ease about the risks of heavy metals in chocolates, it is still good to limit exposures as much as possible where possible. To this end, the WHO and FAO have worked up recommendations for chocolate producers on how to reduce cadmium and lead in their products.

Generally, cadmium primarily gets into chocolate pre-harvest as the cacao plant pulls it up from the soil, while lead is a post-harvest contaminant, primarily from handling of wet beans, such as from dust and soil that gets on the cacao beans as they are dried outdoors.

Simply improving manufacturing processes—removing contaminants during processing and cleaning—can easily reduce lead levels, and some companies are doing a relatively better job at this than others.

But cadmium is a little more difficult. The metal is naturally found in volcanic soil and can spread into agricultural areas via mining, phosphate fertilizers, and municipal sludge. High cadmium levels are almost exclusively found in cacao beans grown in South America, with beans grown in West Africa showing little contamination.

Soil assessments and amendments can help. Planting cacao plants and grafts that take up relatively less cadmium can help, too. Blending high-cadmium cacao beans with low-cadmium beans grown elsewhere is perhaps the easiest way to decrease levels. However, this is not always feasible for high-quality cacao products grown in Latin America.

Practical advice

CR's latest article on heavy metals in chocolates advised readers that "kids and pregnant people should consume dark chocolate sparingly, if at all, because heavy metals pose the highest risk to young children and developing babies."

But medical toxicologists who spoke with Ars disagreed with the "sparingly, if at all" suggestion.

"I don't see evidence that pregnant people or children will be harmed from eating food from time to time with concentrations at the levels described in the article," Stolbach told Ars.

Amirshahi, of Georgetown, agreed, saying she would recommend dark chocolate to children and pregnant people "in moderation."

On a practical note, Amirshahi says indulging during holidays "would not be expected to cause adverse health effects. If you are concerned, enjoy chocolate in moderation. Choose milk chocolate products over dark chocolate and if you have the information available, you can look at the heavy metal content of a particular product."

Given the source of cadmium in chocolate, the cautious can also steer toward fine dark chocolates from beans grown in Africa.

You can look at the extensive testing results of common chocolate products from As You Sow, here.

For those staring at a stash of chocolate from Halloween, Stolbach adds: "My advice to chocolate-eating kids is to eat as much as their parents will let them on Halloween. They have the rest of the year to exercise healthy habits."