Which Foods Are High In Mercury?

Fish is the main source of mercury in the human diet. Large, predatory fish that live a long time tend to have the highest mercury levels. The most common high-mercury fish include king mackerel, shark, swordfish, tilefish, and bigeye tuna.

What Makes a Food High in Mercury?

Mercury gets into water from natural sources like volcanic activity and from human activities like coal burning. Small fish eat tiny plants and animals that have absorbed mercury. Bigger fish eat the smaller fish. The mercury builds up in their bodies over time.

This process is called biomagnification. The larger and older a predatory fish is, the more mercury it tends to carry. The United States Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) have tracked mercury levels in fish for decades. Their data is the standard most doctors and dietitians use.

Which Specific Fish Have the Highest Mercury?

The FDA and EPA group fish into three categories based on mercury levels. The fish to avoid or eat least often are the ones with the highest mercury. King mackerel has some of the highest average mercury levels. Shark and swordfish also test very high. Tilefish from the Gulf of Mexico has the highest mercury of any fish the FDA has tested.

Bigeye tuna is another major concern. This is the kind of tuna used in some sushi and sashimi. It has much higher mercury than the canned light tuna most people buy at the grocery store. Bluefin tuna, often served in high-end sushi restaurants, also contains high mercury levels. The FDA advises young children and people who are pregnant or breastfeeding to avoid these fish entirely.

Orange roughy and marlin are also on the avoid list. These fish live a long time and eat other fish. That means they accumulate a lot of mercury over their lives.

What About Canned Tuna and Other Common Fish?

Canned tuna is the most common source of mercury exposure in the United States. But not all tuna is the same. The FDA reports that canned light tuna has about one-third the mercury of canned albacore (white) tuna. This is because light tuna is usually skipjack tuna, which is a smaller fish. Albacore is larger and lives longer.

The EPA recommends that people who eat fish regularly choose options with lower mercury. Salmon, sardines, trout, and anchovies are all low in mercury. Shrimp, pollock, catfish, and tilapia are also safe choices. The FDA lists these as “best choices” and says you can eat two to three servings per week.

Here is a quick comparison of common fish and their mercury levels based on FDA data:

ppm means parts per million. The FDA action level for mercury in fish is 1.0 ppm. You can see that tilefish, shark, and swordfish all exceed this level.

Are There Non-Fish Foods High in Mercury?

Some people worry about mercury in rice, vegetables, or drinking water. The truth is that these sources are very low compared to fish. Rice does absorb some mercury from soil and water, but the levels are tiny. A study published in the journal Environmental Health Perspectives found that people who eat a lot of rice have slightly higher mercury levels than those who do not. But the increase is small and not considered a health risk for most people.

Drinking water in the United States is tested for mercury. The EPA sets a maximum contaminant level of 2 parts per billion. That is 500 times lower than the action level for fish. Tap water is not a significant source of mercury.

Some herbal supplements and traditional medicines from other countries have tested positive for mercury. This is rare but worth knowing if you take imported supplements. The FDA does not regulate supplements the same way it regulates food, so there is less oversight. If you use any imported herbal products, check the source and ask about testing.

How Much Mercury Is Too Much?

The FDA and EPA have clear guidelines. For women who are pregnant, breastfeeding, or may become pregnant, and for young children, the advice is specific. Eat 2 to 3 servings of fish per week from the “best choices” list. Limit “good choices” to 1 serving per week. Avoid the “choices to avoid” entirely.

For adults who are not pregnant or breastfeeding, the risk is lower. Mercury can still build up in your body over time. The main concern is for your nervous system. High mercury levels can cause numbness, tingling, vision problems, and memory issues. These effects are more serious for a developing fetus or young child because their brains are still growing.

Research published in the Journal of the American Medical Association found that adults with high mercury levels from eating a lot of fish did not show clear neurological harm in most cases. But the same study noted that the effects on developing brains are well established. The point is not to scare you away from fish. Fish is a healthy source of protein and omega-3 fats. The goal is to choose the right fish.

What About Mercury in Sushi?

Sushi can be tricky because the type of fish is not always clear. Tuna sushi is often made from bluefin or bigeye tuna, both of which are high in mercury. Salmon sushi is usually low in mercury. Shrimp, eel, and crab sushi are also low. If you eat sushi regularly, ask what kind of tuna is used. If the restaurant cannot tell you, it is safer to choose salmon or vegetable rolls.

The FDA does not require restaurants to list mercury levels on menus. You have to check for yourself. Some sushi-grade fish like escolar (also called “white tuna” or “butterfish”) are not actually tuna at all. Escolar is a different fish that can cause digestive issues, but it is low in mercury. The confusion shows why it helps to learn the names of the fish you eat.

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