Some canned tuna may contain higher levels of mercury than others, according to new research.
Even high levels are within FDA guidelines, but researchers urge caution for consumers eating tuna products, particularly if pregnant.
Earlier this month, findings from Consumer Reports exposed that some canned tuna products contain high spikes of mercury, which may pose risks to people who are pregnant and to anyone trying to make safe and educated decisions about their diet.
The investigation found that five common tuna brands—Bumble Bee, Chicken of the Sea, StarKist, Safe Catch, and Wild Planet—contained higher than usual mercury levels in some cans, despite the brands’ average low levels.
Consuming high levels of mercury is particularly harmful to people who are pregnant or breastfeeding, as mercury toxicity can impact the fetus’ neurological development, according to the Environmental Protection Agency (EPA).
Because of these risks, the US Food and Drug Administration (FDA) already sets guidelines on how much mercury should be consumed during pregnancy. Per the FDA, a pregnant person should not consume more than 0.46 mc/g of mercury per 4-ounce serving of fish, if eating one serving of this fish a week. If eating two or three servings a week, serving sizes should not contain more than 0.15 mcg/g mercury, according to the FDA.
The spikes found in the Consumer Reports investigation remain safe under FDA guidelines, and the FDA currently lists light canned tuna as a “best choice” option for pregnant or breast-feeding individuals or young children. According to Consumer Reports, however, the FDA guidelines may be in need of a refresh.
You also can’t cook or “burn out” mercury from a product, once it’s there—it’s embedded too deep in the ecosystem.
Mercury is a neurotoxin that comes from coal. When coal burns, mercury rises into clouds in the atmosphere. When it rains, mercury can get into the ocean. Fish can then consume it, changing mercury into a substance called methylmercury. When people consume the fish, they too can ingest the methylmercury.
Mercury poisoning risks are low, but not altogether invisible
Long-term exposure to high levels of mercury can lead to mercury poisoning. This does not happen immediately and can build up over years or decades. Symptoms of mercury poisoning include numbness in certain parts of the body, tremors, difficulty walking, blurry vision, or memory loss. Mercury poisoning from fish is rare in the United States, but consuming fish is not altogether risk-free, according to the Cleveland Clinic.
What this means for you
To help patients make informed nutritional decisions, it may be smart to talk to them about current research studies, FDA guidelines, and their personal health status—especially if canned tuna is a large part of their diet.