Mercury content and serving sizes

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Canned tuna is a healthy and convenient alternative to fresh fish, providing the same low-calorie source of protein, essential nutrients and heart-healthy omega-3 fatty acids. That’s likely why canned tuna is the second most popular seafood product in the United States after shrimp, according to the Office of Sustainable Fisheries.

The U.S. Department of Agriculture recommends that you include fish in your diet, but it’s essential to know which types of tuna are safest and how much is safe to eat. Due to the risk of mercury poisoning, eating tuna daily would exceed the safety limit recommended by the United States Food and Drug Administration (FDA). It depends on the type of tuna you eat. Canned light tuna contains the least amount of mercury, and the FDA suggests limiting yourself to no more than 12 ounces (oz) per week, or no more than three 5-oz cans.

What’s in canned tuna?

Tuna is a member of the Scombrids and are fished commercially throughout the world, in both tropical and subtropical seas. Among the many species, canned tuna is mainly divided into two types.

Skipjack This relatively small fish is the most abundant and widely caught tuna. In the United States, about 70 percent of canned tuna is skipjack. It’s often called light chunk or flake tuna, and producers can it in water, brine or oil.

Albacore It’s bigger than bonito. Its pale flesh has a delicate and sweet taste. Producers often sell albacore as white tuna. The most recent data suggests that about 20 percent of canned tuna consumed in the United States is albacore, although it is now 10 years old. More recent tuna consumption habits may be different.

What about the mercury content?

All fish contain mercury. Knowing which species have the highest levels can help you reduce your risk of mercury poisoning.

Mercury occurs naturally in the environment – for example from volcanic activity – but industrial pollution can also contribute to mercury in the air, according to a study published in 2023. Mercury accumulates in rivers and streams and ends up in oceans around the world, where it turns into methylmercury.

This can build up in the flesh of fish over time after they absorb it from water and food. The amount of mercury in a fish depends on several factors, including where it lives, the quality of what it eats, and the characteristics of the species. In general, the older, larger and heavier a fish is, the more mercury it is likely to contain.

In an effort to help consumers reduce their exposure to mercury while still enjoying the health benefits of eating fish, the FDA has designed a table listing fish species as “best choices”, “good choices” and “choices to avoid” based on their mercury content.

In the study published in 2023, tuna contained the highest mercury content of all fish studied. However, the FDA chart showed that different types of tuna have varying levels of mercury. Each category has specific recommendations for safe consumption, including for children and pregnant people.

How much canned light tuna can you eat per week?

According to the FDA, canned light tuna, made primarily from skipjack tuna, is recognized as a low-mercury fish and is designated a “best choice.”

The FDA recommends eating 2 to 3 servings per week, or about 8 to 12 ounces. This includes people of childbearing age and pregnant people.

An adult serving of fish is the amount that fits in the palm of your hand, or about 4 ounces. Therefore, the recommendation would make consuming two to three 5-ounce cans of light tuna per week safe for adults.

How much canned white tuna?

Because albacore, or white tuna, typically contains three times as much mercury as canned light tuna, the FDA has included it in the “good choice” category. This means the recommendation is one serving per week or 4 ounces for adults, or about one 5-ounce can of albacore tuna per week.

How safe is it for children?

Feeding your child light, protein-rich canned tuna promotes growth and development. The FDA recommends serving fish to your children once or twice a week, using a variety of fish. But portion sizes should be appropriate for the child’s age and total calorie needs.

Portion sizes for children vary by age:

Age (years)

Portion

2 to 3

1 ounce

4 to 7

2 ounces

8 to 10

3 ounces

11+

4 oz

How is the amount calculated?

The FDA’s recommendation for the safe amount of fish to consume is intended as a general guideline based on the average weight of the U.S. population. If you are an adult weighing less than average (165 pounds), you may want to opt for smaller portions or limit your intake to two servings of fish per week instead of three.

If you want a more accurate indication of how much tuna you can safely eat per week, take a look at the tuna calculator created by the Environmental Working Group. It allows you to enter your weight, age, gender and whether you have heart disease.

Based on this information, you can get suggestions on the type and amount of fish you can safely eat, as well as mercury content and sustainability information.

What is the safety standard?

The FDA and the Environmental Protection Agency (EPA) regulate mercury content standards for consumable fish to support public safety. They established the following:

A safe threshold for mercury content in fish is 0.15 parts per million or less.

Moderate to high levels range from 0.16 to 0.46 parts per million

Any fish with a mercury concentration above 0.46 parts per million is not considered safe for consumption.

The level of mercury in a can of tuna can vary somewhat depending on the age of the fish, its size and where it was caught. The EPA and FDA determine averages for each species of fish, which form the basis for regulations and recommendations on safe amounts to eat.

The average mercury concentration in canned light tuna is 0.13 parts per million, and that in canned albacore chunk albacore tuna is 0.35 parts per million, according to the EPA.

Tuna in oil or water?

Water-packed tuna has fewer calories and less fat, which can be helpful if you’re trying to maintain your weight.

For comparison, a can of white tuna in oil, drained, contains 331 calories and 14.4 grams of fat. A can of white tuna packed in water, drained, contains 220 calories and 5.1 grams of fat.

A can of light tuna packed in oil has 339 calories and 14 grams of total fat, while a can packed in water has 191 calories and 1.4 grams of fat.