Heavy metals like lead, arsenic, mercury, and cadmium show up in a surprisingly wide range of everyday foods. Rice, seafood, chocolate, root vegetables, leafy greens, and even spices can contain measurable levels. The metals get into food through contaminated soil, water, industrial pollution, and natural geological deposits, so no single food group is the sole culprit.
Most people’s exposure comes not from one dramatic source but from small amounts across many foods eaten over time. Here’s where those metals concentrate most and what you can do about it.
Rice and Arsenic
Rice is one of the biggest dietary sources of arsenic for most people. Rice plants are unusually efficient at absorbing arsenic from flooded paddy soil, and the grain retains it even after processing. The concern centers on inorganic arsenic, the more toxic form, which makes up a significant share of total arsenic in both white and brown rice.
Brown rice carries more arsenic than white rice because arsenic concentrates in the outer bran layer, which is removed during milling. Research from Michigan State University found that in U.S.-grown rice, inorganic arsenic made up 33% of total arsenic in white rice compared to 48% in brown rice. For rice grown globally, those numbers were even higher: 53% for white and 65% for brown. This doesn’t mean you need to stop eating brown rice, but if rice is a staple in your diet, rotating in other grains like quinoa, barley, or farro reduces cumulative exposure. Rinsing rice thoroughly and cooking it in excess water (then draining) can also lower arsenic levels.
Seafood and Mercury
Fish and shellfish are the primary dietary source of methylmercury, a form of mercury that builds up in fish tissue over time. Larger, longer-lived predatory fish accumulate the most because they eat smaller fish that already contain mercury. The differences between species are dramatic.
FDA monitoring data shows that shrimp, scallops, clams, sardines, and canned salmon all average below 0.02 parts per million (ppm) of mercury. Tilapia, catfish, and pollock stay under 0.04 ppm. These are consistently low-mercury options. In the middle range, canned light tuna averages 0.126 ppm, cod comes in at 0.111 ppm, and freshwater trout at 0.071 ppm.
The fish to limit or avoid are the large predators. Swordfish averages 0.995 ppm, shark 0.979 ppm, king mackerel 0.73 ppm, and bigeye tuna 0.689 ppm. Gulf of Mexico tilefish tops the list at 1.123 ppm. Fresh yellowfin tuna and canned albacore both average around 0.35 ppm, roughly three times higher than canned light tuna. If you eat fish regularly, choosing smaller species gives you the nutritional benefits of seafood with a fraction of the mercury exposure.
Dark Chocolate and Cocoa
Dark chocolate and cocoa powder contain both lead and cadmium, often at levels that raise concern. Cacao trees absorb cadmium from volcanic soils in regions like West Africa and South America, while lead contamination typically happens after harvest, during drying, shipping, or processing.
Consumer Reports testing found that many dark chocolate products exceeded California’s maximum allowable dose levels for lead and cadmium. On average, dark chocolate samples reached nearly twice the lead threshold, with some products hitting more than five times that level. Cadmium levels were somewhat lower but still frequently approached the safety threshold. Cocoa powder showed a similar pattern. The higher the cacao percentage, the higher the metal concentration tends to be. Eating a square of dark chocolate occasionally is a very different exposure profile than consuming large amounts daily or using cocoa powder heavily in smoothies or baking.
Root Vegetables and Leafy Greens
Root vegetables like carrots and sweet potatoes are the most efficient accumulators of lead among common garden crops. Lead binds tightly to soil particles and tends to stay in plant roots rather than moving up into leaves or fruit. Kansas State University research confirmed that root and tuber crops had the highest lead concentrations in their edible portions, followed by leafy vegetables, then fruiting vegetables like tomatoes and peppers.
If you grow food in urban soil, this matters. Old house paint, leaded gasoline residue, and industrial activity can leave soil contaminated for decades. Testing your soil before planting root crops is a practical step, and if lead levels are elevated, switching to raised beds with clean soil or growing fruiting vegetables instead reduces your risk.
Leafy greens like spinach are particularly good at absorbing cadmium and other metals from contaminated soil. Among leafy vegetables studied in contaminated growing conditions, spinach accumulated the highest metal concentrations. For commercially grown greens purchased at a grocery store, contamination levels are generally much lower because they’re grown in agricultural soil rather than industrial or urban land. Washing greens thoroughly removes surface contamination but won’t eliminate metals absorbed into the plant tissue itself.
Spices, Especially Cinnamon and Turmeric
Spices have emerged as an underappreciated source of lead contamination. In late 2023, a major recall of cinnamon applesauce products revealed lead levels in the cinnamon ingredient between 2,270 and 5,110 ppm, extraordinarily high concentrations traced to a supplier in Ecuador. That recall prompted the FDA to test ground cinnamon products more broadly, particularly from discount retail stores.
The follow-up survey found elevated lead in ground cinnamon from six distributors, with levels ranging from 2.03 to 3.4 ppm. While far lower than the applesauce incident, these levels were still high enough for the FDA to recommend recalls and advise consumers to discard the products. Turmeric has faced similar scrutiny in recent years, with lead-based pigments sometimes added to enhance color in certain supply chains.
Buying spices from established brands with supply chain oversight reduces your risk. If you use large quantities of turmeric or cinnamon daily, as some people do for perceived health benefits, the cumulative exposure can become meaningful.
Baby Food and Children’s Exposure
Children are more vulnerable to heavy metals than adults because their smaller bodies absorb metals more readily, and their developing brains are more sensitive to even low-level exposure. The FDA’s “Closer to Zero” initiative has set specific action levels for lead in processed baby foods: 10 parts per billion (ppb) for most categories including fruit and vegetable purees, yogurts, and single-ingredient meats, and 20 ppb for root vegetables and dry infant cereals. Root vegetables get a higher threshold precisely because they naturally absorb more lead from soil.
The FDA is also developing action levels for arsenic and cadmium in baby foods, with draft guidance expected in 2025. For mercury, the primary recommendation remains limiting high-mercury fish. If you’re feeding a young child, offering a variety of foods rather than relying heavily on any single item (especially rice-based cereals or root vegetable purees) is the most practical way to limit exposure across all four metals.
How to Reduce Your Exposure
You can’t eliminate heavy metals from your diet entirely because they’re naturally present in soil and water. But you can lower your cumulative intake with a few straightforward strategies.
- Diversify your grains. If you eat rice daily, rotate in other grains. When you do cook rice, use a high water-to-rice ratio and drain the excess.
- Choose smaller fish. Salmon, sardines, shrimp, and tilapia deliver omega-3s with minimal mercury. Save swordfish and bigeye tuna for rare occasions.
- Moderate dark chocolate. A few squares a few times a week is a different story than daily high-cacao snacking.
- Buy spices from reputable sources. Avoid discount or unbranded ground spices, particularly cinnamon and turmeric, where contamination risk is higher.
- Vary your vegetables. Rotate between root vegetables, leafy greens, and fruiting vegetables rather than relying on any single type.
- Test urban garden soil. If you’re growing food in a city yard, a soil test for lead costs roughly $15 to $30 and can save you from unknowingly eating contaminated produce.
The overall principle is simple: variety is protective. Heavy metals concentrate in specific foods through specific pathways, so eating a wide range of foods naturally dilutes your exposure to any single contaminant.