Mercury in fish: a guide for parents

Fish is worth it

Fish gives children protein, omega-3 fats, iodine, iron, zinc, choline, selenium and vitamin B12, and oily fish also provides vitamins A and D (FDA). The FDA says almost all children eat less fish than recommended. The aim is to choose fish that are lower in mercury, not to skip fish. For when and how to start fish, cooking and bones, see fish for babies.

Where mercury comes from

Mercury occurs naturally and is also released by human activity. In streams, lakes and oceans it’s turned into methylmercury, the form found in fish (FDA). Fish take it in from what they eat, so it builds up most in large fish that eat other fish, and fish that live a long time (FDA). That’s why shark and swordfish are high, and small fish like sardines and anchovies are low.

Methylmercury is a neurotoxin: too much of it over time can harm the brain and nervous system (FDA, EPA). The EPA says unborn babies are the most vulnerable, and a developing brain and nervous system may be more sensitive than an adult’s. That’s why the advice is written for pregnancy, breastfeeding and children. The FDA calls its approach cautious and highly protective: a fish only makes the Best choices list if an average pregnant adult could eat it at least three times a week.

Two facts parents often ask about:

• Cooking and cleaning don’t lower mercury. It’s spread through the whole fish, not just the skin or fat (FDA). Choosing the right fish is what makes the difference.
• One serving of a high-mercury fish isn’t a reason to worry. The FDA says just choose lower-mercury fish from then on.

The three FDA and EPA categories

The FDA and EPA sort fish by mercury level:

• Best choices. Fish your child can have 2 servings a week from. Family favorites include salmon, sardines, cod, pollock, tilapia, freshwater trout, catfish, anchovies, Atlantic mackerel, haddock, herring, canned light tuna, and shellfish like shrimp, crab, scallops, clams, squid and lobster.
• Good choices. Higher in mercury. They include albacore and yellowfin tuna, halibut, snapper, grouper, mahi mahi, rockfish, Chilean sea bass and Spanish mackerel. For adults, the FDA allows 1 serving a week from this list instead, with no other fish that week. Its advice for children is 2 servings a week from Best choices.
• Choices to avoid. Highest in mercury: shark, swordfish, marlin, king mackerel, orange roughy, bigeye tuna and tilefish from the Gulf of Mexico. The FDA says not to feed these to children.

Not on the chart? If a fish, such as mussels, isn’t listed, the FDA says it didn’t have enough reliable mercury data to place it. Our suggestion is to treat it as an occasional food rather than a regular one.

Eating more fish than 2 servings a week? The FDA says children whose diet includes more fish should only have the very lowest-mercury Best choices, such as anchovies, Atlantic mackerel, catfish, clams, crab, flounder, haddock, pollock, salmon, sardines, scallops, shrimp, sole, squid, tilapia, trout and whiting.

How much, by age

The FDA advises 2 servings of fish a week for children, from a variety of Best choices, with portions that fit their age:

• Under 12 months: the FDA gives no serving size. Start with a few flakes and let your baby decide how much to eat. Breast milk or formula is still their main food.
• Ages 1 to 3: about 1 oz (28 g) per serving.
• Ages 4 to 7: about 2 oz (57 g) per serving.

So a week for a 2-year-old might be a small salmon fish cake on one day and some mashed sardines on toast on another, with chicken, eggs, beans or meat on the other days. Varying the type of fish is better than serving the same one every time (FDA).

Tuna: light, albacore and the rest

Tuna is where the categories matter most, because the word “tuna” covers several species (FDA):

• Canned light tuna (often skipjack) is a Best choice. These are generally smaller tuna species.
• Albacore (labeled “white” tuna, canned or fresh) is a Good choice. It’s larger, lives longer and typically has about three times more mercury than canned light tuna.
• Yellowfin is a Good choice.
• Bigeye tuna is a Choice to avoid.

Check the label: “light” or “skipjack” is the lower-mercury canned tuna, and the better everyday pick. Choose tuna canned in water with no added salt, and drain it.

The AAP agrees with the FDA chart: it says “light” tuna is best, and that the FDA and EPA rank canned light tuna among the best choices for children. So canned light tuna can be one of your child’s 2 fish servings a week (about 1 oz, 28 g, at ages 1 to 3). Varying it with salmon, sardines, cod or pollock is still a good idea (FDA). See tuna.

Fish caught by family or friends

Check local fish advisories for that lake, river or coast (FDA, EPA). If there’s no advice, the FDA says children under 6 should have no more than 1 to 2 oz of that fish in a week, and no other fish that week. Larger carp, catfish, trout and perch from local waters are more likely to have advisories (FDA).

What about raw fish?

Mercury is only one reason to be careful. The FDA says children should only eat fish cooked to a safe temperature, so no raw fish such as sushi or sashimi. See sushi.

UK limits for children

The NHS uses fewer categories but gives clear limits:

• Shark, swordfish and marlin: children under 16 should avoid them, because the mercury can affect a child’s nervous system (NHS).
• Oily fish (such as salmon, mackerel and sardines): try to give at least 1 portion a week. Because oily fish can contain low levels of pollutants that build up in the body, boys should have no more than 4 portions a week and girls no more than 2 (NHS). The NHS adds that the health benefits are greater than the risks within these amounts.
• Tuna doesn’t count as oily fish, and the NHS gives no separate tuna limit for children.

Where US and UK advice differs

• Which fish to avoid. The FDA and EPA list seven Choices to avoid, including king mackerel, orange roughy and bigeye tuna. The NHS names shark, swordfish and marlin for under-16s.
• What the limit is about. US advice counts all fish against mercury levels. NHS limits on oily fish are about other pollutants, and are lower for girls because these can build up and affect a future pregnancy.
• Portion size. The FDA gives children’s servings by age (about 1 oz at 1 to 3). The NHS portion is about 140 g (5 oz), an adult serving, so for toddlers count the number of small servings, not grams.
• Tuna. The FDA and the AAP list canned light tuna as a Best choice for children. The NHS gives no tuna limit for children and doesn’t count tuna as oily fish.