The Dark Side of Chocolate: Heavy Metals in Your Favorite Sweet Treat

People look to dark chocolate as a better-for-you dessert for its potential health benefits, in the form of antioxidants, flavanols, fiber, and relatively low levels of sugar. But new consumer data shows that there are concerningly high levels of harmful heavy metals lead and cadmium hiding in many chocolate bars.

How much risk is actually involved for you? We'll talk about the health effects of heavy metal accumulation, whether you should consider avoiding dark chocolate, and signs of a heavy metal toxicity. If you’re concerned about heavy metal exposure, we'll explain how you can get testing for heavy metals in functional medicine, and ways you can reduce your exposure.

Are your issues related to heavy metals? Get started with a detox by speaking with a practitioner.

Heavy metal contamination in dark chocolate

Researchers tested 28 dark chocolate bars for lead and cadmium.

To determine the potential risk posed by the chocolate tested, scientists used California's maximum allowable dose level (MADL) for lead (0.5 mcg) and cadmium (4.1 mcg). Since there are no federal limits set for the amount of lead and cadmium most individual foods can contain (besides those intended for use in infants and children), researchers chose this metric believing it offers “the most protective standards available” (1,2,3). 

Some of the highlights of their findings include:

  • For 23 of the bars, eating just an ounce per day would put an adult over a level that public health authorities say may be harmful for at least one of the heavy metals.
  • Five of the bars were above safe levels for both cadmium and lead.
  • Cadmium and lead were present in all bars tested.

Dark chocolate tends to be higher in heavy metals than milk chocolate, probably because of its higher cacao content, since the heavy metals are found in the beans themselves. For reference, dark chocolate tends is generally considered at least 65% cacao by weight.


Lead contaminates the cocoa beans through the environment when it's carried by the wind from surrounding areas as the beans dry out in the open.


Cadmium appears to come from soil contamination, which is then drawn up through the roots of the plant and ends up in the beans. Processing removes some of the cadmium present in cocoa beans.

Related: Can Toxic Overload Lead to Infertility?

Many foods contain trace amounts of heavy metals

Many foods have low levels of heavy metal contamination present, including some that are considered healthy, for example, mercury in fish and cadmium in shellfish.

To assess the overall risk of these heavy metals you'll inevitably encounter in your diet, the question is whether or not the benefits of the food outweigh the risks. For many healthy foods, surprisingly, the answer is yes—including for small fish and shellfish, consumed in moderation.

It's important to note though that other foods may not have the antioxidant potential to balance out the potential risks, (i.e. corn, carrots, potatoes) and small amounts from multiple sources can add up to problematic levels.

Read: Boost Antioxidants in the New Year with Liposomal Glutathione

The bioavailability of lead and cadmium in dark chocolate is low

How much lead and cadmium your body actually absorbs from eating dark chocolate is quite a bit lower than the amount of lead and cadmium the chocolate actually contains. For example, most of the lead that enters the body is excreted in urine or with bile (and ultimately via stool) (4). Heavy metal absorption is also affected by the method of exposure (inhaled vs. eaten), and the particle size.

For dark chocolate, one systematic review found the bioavailability of lead was around 12-14%, while that of cadmium was around 50% (5).

When adjusting for bioavailability, the same review showed that cadmium intake from dark chocolate contributed to 17% of the Tolerable Weekly Intake, a measure established by the World Health Organization (5).

Shop: Clear Change 10-Day Metabolic Detox with easy-to-follow instructions, menu plans, and recipes.

Chocolate is also high in beneficial minerals, antioxidants, and polyphenols.

The benefits of reaching for dark chocolate after a meal in the place of a sugar-laden dessert likely still outweigh any risks for most people.

Dark chocolate’s reputation as a healthier treat comes mostly from the cocoa solids. These are packed with antioxidants like PQQ and polyphenols linked to improved blood vessel function, healthy mitochondria function, reduced inflammation, and lower cholesterol (6,7). 

Dark chocolate is also lower in sugar and higher in fiber than milk chocolate, and it has minerals like magnesium and potassium.

Related: How to Biohack Your Brain to Be Smarter & Happier

Should you be concerned about heavy metals in your food or environment?

Heavy metals are commonly found in the environment and our diet. Some examples include: mercury, lead, arsenic, cadmium, chromium, and thallium.

Note: Heavy metals are called such because they’re “heavy” in comparison to water, meaning that they have a higher molecular weight than 18 g/mol.

Heavy metals contaminate drinking water sources and soil systems via wastewater, sewage, industrial activities, and mining operations. People are exposed to heavy metals in a few different ways, primarily through drinking water or eating food grown in contaminated soil.

Read: How to Avoid These Toxic ‘Forever Chemicals’

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Many heavy metals are poisonous to humans, even in small concentrations

Heavy metal toxicity can affect your brain, lungs, kidney, liver, blood composition and other important organs, as well as your energy levels. If heavy metal poisoning is chronic, it can contribute to a serious decline in physical health often resembling diseases such as Multiple Sclerosis, Parkinson’s disease, Alzheimer’s disease and Muscular Dystrophy.

Heavy metals are also considered carcinogenic due to oxidative stress and their potential to damage DNA. The danger is greatest for pregnant people and young children because the metals can cause developmental problems, affect brain development, and lead to lower IQ.

Some people are genetically predisposed to heavy metal poisoning. A qualified functional doctor can help you determine if this is the case, and whether you should seek help to minimize exposures and reduce heavy metals already present in your body.

Are you genetically susceptible to heavy metals? Read more.

Symptoms of heavy metal poisoning

When your body’s heavy metal burden exceeds the threshold of normal detoxification pathways, it kicks the immune system into overdrive as it struggles to keep up.

Signs & symptoms of heavy metal toxicity include (8):

  • Headaches
  • Irritability
  • Brain fog or difficulty concentrating
  • Trouble losing weight
  • Chronic nasal/sinus congestion
  • Skin issues (breakouts, eczema, redness)
  • Digestive problems (diarrhea, indigestion, acid reflux, etc.)
  • Abdominal pain
  • Nausea or vomiting 
  • Fatigue
  • Numbness or tingling in hands or feet
  • Miscarriage or infertility

These symptoms, if caused by toxic heavy metals, can lead to increased inflammation and significant dysregulation in immune system function, especially if long-term exposure is a factor.

Heavy metal testing

A heavy metal test measures multiple heavy metals using a blood or urine sample. When doing a heavy metal toxicity test you may also be asked to include hair or fingernails.

Heavy metal detoxing

To rid the body of heavy metals, prioritize detoxification pathways in the liver, cells, and digestive system.

Digestive detox

Your gut is your immune system’s first line of defense, and is responsible for properly eliminating most dangerous heavy metals. If you struggle with constipation or aren’t going regularly, this pattern is more than just uncomfortable—you’re actually not eliminating necessary waste.

Healthy bowel movements help your body get rid of things we don’t need–-including environmental pollutants, waste products from pharmaceuticals, and even excess hormones make their way out of our body this way. 

Your gut works with the gallbladder, liver, and intestines to detox, but if not functioning optimally, harmful toxins get stuck in a pattern of “recirculation”.

To avoid recirculation and prepare toxins like heavy metals for excretion, we can use what are called “binders”. Toxins should first be processed by the liver, “bound” in the intestines, and then passed with our stool. But if they’re not, they’re reabsorbed into the liver, and this places immense stress on the body. Binders include fulvic or humic minerals, activated charcoal, or certain clay powders

Support digestive detox with:

  • Addressing underlying digestive issues like sensitivity to gluten or dairy, leaky gut, or intestinal inflammation
  • Detox binders, like certain clays, to absorb toxins along the digestive tract
  • Fiber to add bulk to stool and encourage bowel regularity
  • Prebiotic fiber and probiotic bacteria to balance gut health in the long term

Shop: G.I. Detox+

Heavy metal liver detox

Your liver is a detox powerhouse. It’s the largest internal organ, and is responsible for filtering toxins, fats, proteins, blood, and more. Detoxification in our liver happens in a two-stage process—Phase 1 and Phase 2—and each phase has different requirements (9). 

To support phase one:

  • Cruciferous vegetables (broccoli, cauliflower, cabbage, etc.)
  • Green tea
  • Milk thistle
  • Rosemary
  • Garlic
  • Astaxanthin
  • Turmeric
  • Dandelion root
  • N-Acetyl Cysteine

To support phase two:

  • Milk thistle
  • Turmeric
  • Essential Amino Acids such as glycine, glutamine, cysteine, and taurine
  • Cruciferous vegetables
  • Resveratrol
  • Alpha Lipoic Acid
  • B vitamins – Folate, B6, B12
  • MCT oil

There are many enzymes and specific cofactors necessary for optimizing liver detoxification. Optimizing glutathione levels with precursors such as NAC (N-acetyl cysteine) and/or IV glutathione or liposomal preparations is critical.

IV Therapy 

IV drips deliver nutrients directly to the cells that need them, bypassing slow and ineffective digestion processes. Glutathione is the body’s strongest antioxidant and detoxifier, and is one of the most popular and beneficial IV boosts available. 

Learn more about our Recharge Drip, the Cold & Flu Buster, and the increasingly popular Weight Loss Drip.

Comprehensive Detox System

For a comprehensive detox support system that upregulates Phase 1 and Phase 2 detox enzymes, Metagenics Clear Change is a 10-Day metabolic detox with easy-to-follow instructions, menu plans, and recipes to support healthy detox pathways in the gut and liver.

Protecting your body from heavy metal accumulation

While it’s not possible to avoid every toxin in your environment, you don’t have to live in a bubble to make an impact. Reduce your heavy metal exposure by making a few changes to your daily routine.

Filter your air and water

Remove various toxins and heavy metals from your home drinking water with a reverse osmosis or granular activated carbon (GAC) water filter.

Indoor air is also one of the top offenders for toxin exposure, containing up to 5x more pollutants than outdoor air. Change household filters often, and make sure they’re rated to filter mold, and other household airborne contaminants.

Choose organic produce when able

Most of the pesticides and heavy metals were exposed to find their way into our bodies via contaminated food and produce. If budget is a concern, consult the Environmental Working Group’s “Clean 16” list for fresh produce which is less likely to have pesticide residue.

Solid minerals can block heavy metal absorption

Toxic metals can be taken up into cells in place of essential minerals, leading to either toxicity or deficiency. However, consuming a high enough amount of minerals (magnesium, iron, calcium), may decrease the potential toxicity of heavy metals because minerals take priority at the binding site (10). For example, studies have found that those consuming a calcium-poor diet absorb more lead than those who have a calcium-rich diet (11). And, iron deficiency leads to an increase in lead absorption and cadmium absorption (12).

Use non-toxic household & personal care products

Swap body care products for those without parabens, phthalates, or other endocrine-disrupting compounds. Be mindful of household cleaning products that can harm bodily tissues if inhaled or when they come in contact with skin.

Functional medicine for heavy metal exposure

If toxic metals are your medical issue and the root of inflammation and chronic disease, the next step is to develop a comprehensive treatment plan to address metal toxicity by addressing:

  • Diet
  • Body fat levels where toxins are often stored
  • Infrared saunas, sweat, and exercise 
  • Supplements such as activated charcoal, calcium-d-glucarate, and liposomal glutathione or NAC
  • IV glutathione and/or DMSA chelation

Don’t let heavy metal accumulation lead to troubling symptoms. If you suspect heavy metal contamination or that you have a high toxic burden, contact a qualified functional medicine provider at CentreSpringMD today.




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