Heavy Metals in Food: Lead, Cadmium, Arsenic and Mercury

Heavy Metals in Food: Lead, Cadmium, Arsenic and Mercury

Small amounts of lead, cadmium, arsenic and mercury are found in many everyday foods because they occur in soil, water and air. Dark chocolate, rice, seaweed and some fish are well-known sources. You can't avoid them entirely, but eating a varied diet, choosing lower-mercury fish and cooking rice in extra water lowers your exposure.

This guide is for anyone who has seen headlines about metals in chocolate, rice or baby food and wants to know what is a real concern and what practical steps make a difference.

Key takeaways

  • Lead and cadmium get into food mainly because plants take them up from soil and water and animals eat those plants, according to the FDA.
  • Cadmium levels in chocolate depend on where the cocoa was grown and the percentage of cocoa solids, so darker chocolate can carry more.
  • Inorganic arsenic is highly toxic, and crops such as rice take it up from contaminated irrigation water, according to the WHO.
  • The FDA advises adults who are or might become pregnant or are breastfeeding to eat 2 to 3 servings a week of fish from its "Best Choices" list, with a serving of 4 ounces.
  • The FDA says detecting a metal in a food does not necessarily mean the food should be avoided; eating a variety of nutrient-dense foods limits exposure to any single contaminant.

How do heavy metals get into food?

Heavy metals get into food from the environment. Plants absorb them from soil and water, animals eat those plants, and some foods and cookware add more along the way.

"Heavy metals" is an everyday term for metals and metal-like elements that can be toxic at low levels. The FDA calls them toxic elements. The four that matter most in food are lead, cadmium, arsenic and mercury.

The FDA explains that lead can be taken up by plants and eaten by animals, and that levels are higher in some regions because of past uses of lead in paint, gasoline and plumbing. Lead can also leach from some pottery glazes and from certain imported cookware made from aluminum, brass and related alloys.

For cadmium, the FDA says levels are higher where some phosphate fertilizers are used and near smelting, mining and fossil fuel burning. Arsenic enters crops largely through water: the WHO describes crops such as rice taking up arsenic from irrigation water. Mercury builds up in fish, which we cover below.

The same soil-and-water route applies whether food is grown conventionally or organically, which is one reason organic labels don't solve this problem. Our article on when it's fine to skip organic looks at what that label does and doesn't cover.

Which foods contain the most heavy metals?

The main sources people ask about are chocolate and cocoa, rice and rice products, seaweed, some spices and large predatory fish. The table summarizes what official sources say about each.

MetalNotable food sourcesMain health concerns
LeadFoods grown in contaminated soil; food in some ceramic ware and imported cookware; ground cinnamon is monitored by the FDABrain development in children (learning, behavior, IQ); kidney function and blood pressure in adults
CadmiumChocolate and cocoa (depends on origin and cocoa content); seaweed; crops grown where cadmium is highKidney dysfunction and bone demineralization
Arsenic (inorganic)Rice and crops irrigated with contaminated water; contaminated groundwater; seaweedSkin lesions and skin cancer; bladder and lung cancer with long-term exposure
Mercury (methylmercury)Large predatory fish such as bigeye tunaHarm to the developing child before birth and early in life; nervous system effects

The table draws on FDA pages for lead and cadmium, and WHO fact sheets on arsenic and mercury.

Is there lead and cadmium in dark chocolate?

Yes, dark chocolate can contain both, and darker chocolate tends to carry more cadmium because it contains more cocoa solids. For most adults, an occasional square is not a major source.

The FDA's cadmium page says chocolate levels "depend on the growing area and the percentage of cocoa solids," and notes that the WHO describes chocolate as a minor source of cadmium exposure internationally. The FDA's lead page also lists published research measuring cadmium and lead in US cocoa powder and chocolate products.

Cadmium matters because the body clears it slowly. The FDA says it can build up in the kidneys and liver over years of low-level exposure, and that the kidneys and bones are the most sensitive targets. For smokers, though, tobacco smoke is the main source of cadmium, far more than food.

Practical takeaways: treat dark chocolate as a treat rather than a daily health food, keep portions small, and vary the brands and origins you buy instead of eating the same bar every day. Children and pregnant women have the most reason to keep amounts modest because lead's most serious effects happen during brain development.

How much arsenic is in rice, and how can you reduce it?

Rice is a well-known arsenic source because the plant takes up arsenic from irrigation water. Cooking it in plenty of water and draining it, and eating a variety of grains, both reduce how much you take in.

The WHO notes that arsenic is "highly toxic in its inorganic form." Long-term exposure is linked to skin lesions and skin cancer, and to bladder and lung cancer. The WHO estimates that about 140 million people in at least 70 countries have been drinking water with arsenic above its guideline of 10 micrograms per liter. If you rely on a private well in an area with known arsenic, testing your water matters more than any rice tip.

For rice itself, the FDA's arsenic page cites a study showing that cooking rice in excess water, like pasta, then draining it reduces arsenic. The same study found it also reduces the vitamins added to enriched white rice, so it's a trade-off. The FDA's main advice is to eat a variety of nutrient-dense foods across and within food groups.

Swapping some rice for other grains spreads the risk. Our article on whether millet is a healthy grain covers one easy alternative, along with oats, barley, quinoa and bulgur.

Which fish are lowest in mercury?

Smaller fish lower on the food chain, such as salmon, sardines, anchovies, shrimp, tilapia and canned light tuna, are among the FDA's "Best Choices." Large predatory fish such as bigeye tuna carry the most mercury.

The WHO explains that people are exposed to methylmercury, the organic form of mercury, mainly by eating fish and shellfish, and that large predatory fish are more likely to have high levels because they eat many smaller fish. Exposure before birth poses a particular threat to the developing child.

The FDA and EPA advice on eating fish recommends that adults who are or might become pregnant or are breastfeeding eat 2 to 3 servings a week from the "Best Choices" category, with a serving of 4 ounces measured before cooking. Children should have 2 servings a week from "Best Choices," with serving sizes of about 1 ounce at ages 1 to 3, 2 ounces at 4 to 7, 3 ounces at 8 to 10 and 4 ounces from age 11. Best Choices include anchovies, Atlantic mackerel, catfish, clams, crab, salmon, sardines, scallops, shrimp, sole, squid, tilapia, trout and whiting. Bigeye tuna is in the "Choices to Avoid" group, and tilefish from the Gulf of Mexico has higher mercury levels.

Fish is still worth eating for its omega-3 fats and protein. Our comparison of farmed and wild salmon and our look at whether plant foods can replace salmon for omega-3s can help you choose.

How to reduce heavy metal exposure: a practical checklist

  1. Eat a varied diet. The FDA's core advice is variety within and across food groups, so no single food dominates your exposure.
  2. Rotate your grains. Don't rely on rice, rice cakes and rice milk every day; mix in oats, barley, millet, quinoa and wheat.
  3. Cook rice in extra water and drain it, accepting some loss of added vitamins in enriched rice.
  4. Pick lower-mercury fish from the FDA's Best Choices list, and follow the serving sizes for children.
  5. Keep dark chocolate and seaweed snacks occasional, and vary brands and origins.
  6. Check your cookware and dishes. Avoid storing or cooking acidic food in decorative or imported ceramics and metal cookware of uncertain origin.
  7. Test well water if you use a private well, especially in areas known for arsenic.
  8. Don't smoke. For smokers, tobacco is the main source of cadmium.

Parents of babies and toddlers have extra reason to vary first foods; our article on nutrition in US baby foods covers related concerns.

Common mistakes

  • Cutting out healthy foods in fear. The FDA says testing results that detect metals do not necessarily mean the food should be avoided. Dropping fish or vegetables can do more harm than good.
  • Swapping one rice product for another. Rice cakes, rice milk and rice pasta all come from rice, so switching between them doesn't spread your exposure. Variety across different grains does.
  • Assuming supplements are clean. Supplements are not reviewed before sale. Look for third-party testing; our piece on supplement sourcing explains what labels can tell you.
  • Using home detox kits or chelation products. These are not a way to deal with dietary metals and can be harmful without medical supervision.

When to see a doctor

Ordinary dietary exposure rarely causes symptoms, so see a doctor if you're worried about a specific exposure or notice warning signs:

  • A child who has eaten paint chips, used imported remedies or spices of uncertain origin, or lives in an older home with peeling paint: ask about a blood lead test.
  • Developmental delays, learning or behavior changes in a child.
  • Persistent stomach pain, nausea, vomiting or diarrhea after eating a particular product.
  • Numbness or tingling, tremors, memory problems or unexplained fatigue.
  • Pregnancy or planning a pregnancy, if you eat a lot of fish or rice and want tailored advice.
  • Drinking water from a well that tested high for arsenic or lead.

Your doctor can order blood or urine tests when there's a clear reason. Kidney health is one of the long-term concerns with cadmium and lead; our guide to simple habits for healthy kidneys covers everyday protection.

FAQ

Is it safe to eat dark chocolate every day?

A small piece is unlikely to be a major source of metals for most adults, and the WHO describes chocolate as a minor source of cadmium internationally. Cadmium rises with cocoa content, so very dark chocolate eaten daily in large amounts adds up. Keep portions small, vary brands, and be more cautious for children and during pregnancy.

Does washing rice remove arsenic?

Rinsing removes some surface starch, but the method with evidence behind it is cooking rice in excess water and draining it, as with pasta. A study cited by the FDA found this reduces arsenic, but it also lowers the added vitamins in enriched rice. Eating a variety of grains is the simplest overall strategy.

Which canned tuna is lowest in mercury?

Canned light tuna is in the FDA's "Best Choices" category, which means adults who are or might become pregnant or are breastfeeding can eat 2 to 3 servings a week of Best Choices fish. Bigeye tuna is a "Choice to Avoid." Mixing tuna with other low-mercury fish such as salmon and sardines spreads exposure further.

Should I get tested for heavy metals?

Most people don't need routine testing for dietary exposure. Testing makes sense when there's a specific reason, such as a child exposed to old paint, contaminated well water, or symptoms your doctor wants to investigate. Avoid direct-to-consumer hair or urine tests that aren't ordered by a clinician, because results are hard to interpret.

What to do next

  • Look at how often rice, rice snacks and rice milk appear in your week, and swap some for other grains.
  • Print or save the FDA's Best Choices fish list and use it when shopping.
  • Test your water if you use a private well.
  • Read more on other contaminants in our explainer on microplastics in the human body.

This article is for general information and is not medical advice.

Sources

Last reviewed: October 2026.

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