Chocolate – Still a Snack

In my recent books, I’ve been including recommendations for dark chocolate as a snack, always in the context of a discussion of its brain health benefits. Recently, news reports have called attention to high levels of heavy metals in cocoa and chocolate, especially lead and cadmium. And this has become a growing concern.

These heavy metals may well pose significant health risks. Cadmium is toxic to the kidneys as well as bones, while both cadmium and lead are classified as neurotoxins that can impair cognitive function and promote neuroinflammation, particularly with chronic exposure. Lead is especially harmful to developing brains, but even in adults it may interfere with neurotransmitter signaling and promote damaging oxidative stress.

These metals can find their way into chocolate in different ways. Cadmium accumulates in the cacao plant from naturally contaminated soil, especially in volcanic regions such as those in Peru and Ecuador. Lead contamination, on the other hand, typically occurs after harvest, when cacao beans are dried outdoors and exposed to lead-laden dust or come into contact with machinery or storage containers that contain lead. These factors result in a wide variation of contamination levels among different brands and sources. Independent testing, including from Consumer Reports and the nonprofit As You Sow, has revealed that many popular dark chocolate brands contain cadmium and lead levels that exceed California’s safety thresholds.

Despite these concerns, it’s worth remembering why cocoa remains a valuable food for brain health. Cocoa is rich in flavanols, especially epicatechin, which have been shown to improve blood flow to the brain, enhance cognitive function, and protect neurons from inflammation and oxidative stress. Cocoa also contains magnesium, essential for brain energy metabolism, as well as theobromine, a mild stimulant that can lift mood and improve alertness.

Randomized controlled trials support cocoa’s role in brain health; for instance, a 2015 study in the American Journal of Clinical Nutrition demonstrated improved cognitive scores in older adults consuming high-flavanol cocoa daily. These benefits, however, don’t require large doses, and can be achieved with modest daily intake. As the authors stated:

“This dietary intervention study provides evidence that regular cocoa flavanols consumption can reduce some measures of age-related cognitive dysfunction, possibly through an improvement in insulin sensitivity. These data suggest that the habitual intake of flavanols can support healthy cognitive function with age.”

To minimize exposure to heavy metals while still enjoying cocoa’s cognitive perks, several steps can help. Choose chocolate made from West African cacao, such as from Ghana or Côte d’Ivoire, as beans from these regions typically contain less cadmium than those from Latin America. Look for brands that clearly state their cocoa origin and sourcing practices. Refer to updated independent testing from organizations like Consumer Reports, which identified safer options including Taza Chocolate Organic Deliciously Dark 85%, Ghirardelli Intense Dark 86%, Mast Organic 80%, and Valrhona Abinao 85%. Certified organic and small-batch brands are not immune to contamination but may adhere to better soil and post-harvest handling standards. Stick to reasonable portion sizes (about 20 to 30 grams per day) to reduce cumulative exposure. Rotate your chocolate brands periodically to prevent repeated exposure from a single contaminated source.

Beyond sourcing, support your body’s ability to detoxify by consuming a nutrient-dense diet rich in zinc, selenium, fiber, and antioxidants. Maintaining a healthy gut microbiome may also reduce absorption of ingested cadmium and assist in excretion. For those with long-term high chocolate intake or known exposure risks, laboratory testing for heavy metals in blood or urine may help guide decisions. This is always worth doing. In fact, I recently underwent bloodwork showing a slightly elevated mercury, likely a consequence of my tendency to favor seafood.

Heavy metal contamination in chocolate is a legitimate issue – no argument there. But it’s not a reason to eliminate dark chocolate altogether. With careful brand selection, mindful portion sizes, and supportive dietary strategies, it is entirely possible to enjoy the well-described neuroprotective benefits of cocoa without the toxic burden.