Eating seafood, especially fish, offers numerous benefits. However, a recent report indicates that fish, particularly tuna, contains high levels of mercury, posing a potential threat to health.
Fish provides many health benefits. For example, most fatty fish are rich in omega-3 fatty acids, which can help reduce the risk of heart disease and support cognitive health.
The omega-3s found in fish may also decrease the risk of depression and improve mental health. Although fish is beneficial for health, it can also increase your exposure to mercury.
Tuna is one of the fish with the highest mercury content. (Image: Shutterstock).
In fact, according to the Environmental Health Perspectives (USA), the consumption of fish is responsible for over 90% of mercury exposure cases in the United States, with tuna being one of the fish with the highest mercury levels.
We know that tuna and other fish contain mercury, but can we suffer from mercury poisoning from eating too much fish?
Mercury Levels in Tuna
Consumer Reports (CR) recently published a report on mercury levels, a neurotoxin, in five different brands of canned tuna. They also examined various types of tuna such as albacore, light tuna, and skipjack.
CR found that all five brands of tuna contained mercury. On average, albacore tuna has mercury levels three times higher than light tuna or skipjack. However, all types and brands of tuna contain some level of mercury.
Albacore tuna raises the most concerns due to its mercury levels being three times higher than light tuna and skipjack. (Image: Shutterstock).
Researchers from CR are concerned that the mercury levels found in certain cans of tuna pose potential dangers.
While some types of tuna are known to have lower mercury levels than others (light tuna has less mercury than albacore), some cans were found to have unexpectedly high mercury levels.
In fact, researchers discovered that 6 out of 30 cans of tuna contained this toxin. Given this unpredictability, experts at CR recommend that pregnant individuals avoid tuna altogether if possible, while other adults should consume tuna in moderation.
Dr. James E. Rogers, Director of Research and Food Safety Testing at CR, stated in a report about the study: “Mercury levels can spike from can to can in unpredictable ways. This can pose health risks to the fetus.”
However, we still need to learn more about the risks associated with adult consumption of tuna and mercury. A specific question arises: does eating too much tuna actually lead to mercury poisoning?
Why Does Tuna Contain Mercury?
According to CR, you cannot completely avoid mercury when consuming seafood. Mercury is always present in oceans due to its natural mineral state as well as human-induced pollution. Generally, larger fish tend to have higher mercury levels because they eat smaller fish and absorb the mercury contained in them.
Mercury is always present in seafood. (Image: Shutterstock).
According to a paper from Biological Trace Element Research, tuna not only accumulates mercury from eating other fish but this mineral also builds up in tuna’s tissues because this type of fish cannot easily eliminate mercury. The combination of these factors results in increasingly high mercury levels in tuna.
How Does Mercury Harm the Body?
According to the U.S. Environmental Protection Agency (EPA), mercury is considered a neurotoxin that can have negative health effects if consumed in larger quantities. Mercury can lead to the loss of brain cells, motor skill impairment, memory loss, anxiety, and an increased risk of heart disease.
Specifically, methylmercury is the form of mercury found in seafood and fish such as tuna. High levels of methylmercury can lead to poisoning. The EPA states that symptoms of methylmercury poisoning include impaired speech or hearing, peripheral vision loss, muscle weakness, and a tingling sensation in the body.
But when should you stop eating, or how can you know how much mercury can lead to poisoning? Unfortunately, there is no clear measure to determine how much tuna you can eat before risking mercury poisoning.
However, the U.S. Food and Drug Administration (FDA) has issued some basic guidelines you can follow to reduce the risk of poisoning.
FDA Recommendations
The FDA states that adults can consume fish with lower mercury levels 1-2 times a week. Pregnant or breastfeeding individuals should eat low-mercury fish 2-3 times a week and should limit their intake to 113 grams of fish per week.
Pregnant or breastfeeding individuals should be particularly cautious about their tuna intake. (Image: Shutterstock).
CR advises pregnant individuals to avoid tuna altogether due to the unstable mercury levels found in canned tuna.
If you frequently consume a lot of tuna, be aware of potential signs of mercury poisoning in your body and talk to your doctor if you are concerned about the amount of tuna you are eating.
Seafood with Lower Mercury Levels
It is important to remember that whenever you consume seafood, you are at risk of introducing mercury into your body.
However, some types of fish and shellfish contain lower mercury levels than tuna. According to CR, crab, shrimp, squid, tilapia, cod, salmon, oysters, and lobster all have lower mercury levels.
If you are looking for canned products with lower mercury levels than canned tuna, consider options like anchovies or canned sardines.
Canned sardines or anchovies are safer options than tuna as they contain lower mercury levels. (Image: Shutterstock).
While you cannot precisely predict how much tuna could lead to mercury poisoning, it is essential to understand that higher mercury levels can have negative health impacts.
Be attentive to symptoms of mercury poisoning and try to adhere to the recommended fish portions each week to avoid excessive mercury exposure.
