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Cadmium in Dark Chocolate: Soil, Cocoa Share and What FDA Says

Eyal Barta •
#Heavy Metals#Cadmium#Chocolate

The FDA’s page on cadmium in food sums up the chocolate question in one sentence: cadmium levels depend on the growing area and the percentage of cocoa solids in the chocolate product. The same page says experts around the world have found that chocolate is a minor source of exposure to cadmium internationally.

What the FDA page says, and where its number comes from

The FDA admits that cadmium in chocolate has been the subject of considerable media attention. It puts chocolate right after seaweed, which it uses to show that detection of a contaminant does not make the food necessarily bad for you if eaten as part of a varied diet.

When the page gives a figure for dark chocolate, it is an international one. FDA experts take part in the Codex Alimentarius Commission, and Codex has recommended maximum cadmium levels for chocolate in international trade, ranging from 0.7-0.9 mg/kg for dark chocolates.

So the chocolate figure on the FDA page is a Codex recommendation for international trade. That doesn’t mean the agency is ignoring chocolate. It means the FDA treats chocolate as one food it monitors, not as a special case.

Why cadmium levels track cocoa content and growing region

The cocoa-content part is simple: a higher cacao percentage means more of the bean and more of whatever the bean took up. Growing region is the more interesting part. ATSDR notes that worldwide, there are areas with very high levels of cadmium in the soil, and that crop uptake in those areas can lead to significant dietary exposures. For most people, its summary says, cadmium exposure comes primarily by eating certain foods if grown in contaminated soil.

Soil isn’t the whole story. A PMC-published analysis notes that several authors have noted that heavy metal contamination of dark chocolate and other cocoa products is chiefly the result of post harvesting contamination. Its authors also point to farms and processing plants sitting near industrial facilities as a driver of heavy metal contamination in dark chocolate. The same study found that “organic” products were significantly more likely to demonstrate higher levels of cadmium. Shoppers who treat the organic label as a proxy for low metals should take note.

How the FDA monitors cadmium in chocolate

The FDA says it tests foods for cadmium to monitor the safety of the U.S. food supply, enforce FDA regulations, inform agency guidance to industry, and give the public science-based information. The work runs through three channels:

  1. The Total Diet Study
  2. The FDA’s Toxic Elements in Food and Foodware, and Radionuclides in Food Compliance Program
  3. Other surveys, run annually or in response to reports of elevated levels in specific products

Testing can happen at FDA laboratories, laboratories we contract with, or at state laboratories under cooperative agreements. It can be aimed at a category such as foods commonly eaten by children under 2 years of age, or set off by reports of high heavy-metal levels. For interim reference levels and action levels, the agency points readers to Closer to Zero. For its own interim reference level for cadmium, the FDA has adopted a toxicological reference value range of 0.21-0.36 micrograms per kilogram of body weight per day. It also links its research on reassessing the cadmium toxicological reference value and the 2022 Meeting Materials, Science Board to the FDA for background.

(Lead, the other metal in these headlines, is a separate topic. In the same study of 72 cocoa products, 43% exceeded California’s Prop 65 level for lead, while 70 of 72 fell below FDA’s interim reference level for lead.)

What does cadmium in chocolate mean for an ordinary eater?

In the study of 72 products, more than half of products tested may pose no appreciable risk for the average person at a single serving. The authors also warn that eating some of those products, or more than one serving per day in combination with non-cocoa derived sources, could push exposure past California’s Prop 65 limits. The study’s yardstick was California’s Prop 65 maximum allowable dose level (MADL) for cadmium, 4.1 mcg a day; 35% of the products tested exceeded it.

That benchmark is useful context but easy to misread. ATSDR puts typical dietary cadmium intake at about 30-50 micrograms per day, with healthy people absorbing 1-10% of what they swallow. A separate ATSDR page gives about 6% for normal absorption, rising to up to 9% in people with iron deficiency. It also says cadmium in food is absorbed less readily than cadmium in water, at 5% in water versus 2.5% in food.

Accumulation is the reason to pay attention at all. Cadmium’s half-life in the kidney is between 6 to 38 years, and the kidneys and liver together hold about 50% of the body’s stored cadmium. Smoking makes a bigger difference than chocolate does. A cigarette contains about 2.0 µg of cadmium, and smokers typically carry more than double the body burden of nonsmokers.

The practical read

ATSDR says background cadmium in food, water and air is not a health concern for the general North American population. That isn’t permission to ignore it. The things you control are the ones the FDA names: how much cocoa is in the bar and how often you eat it, inside a varied diet. If you eat a lot of high-percentage dark chocolate, the habit is the thing to look at, not any single bar. Whether the FDA will ever set a U.S. cadmium limit just for chocolate is speculation.

Sources

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