By Lori Zanteson, Environmental Nutrition Newsletter
December 4, 2020

Opt for Low-Mercury Fish Choices

We know fish is important for health — high in protein, low in saturated fat, a good source of heart-healthy omega-3 fatty acids, and rich in vitamins, such as vitamins D and B2, and minerals, including iron, iodine, magnesium, and potassium. Research shows that eating fish once or twice a week may reduce risk of several chronic conditions, including stroke, depression, Alzheimer’s disease, and in the case of fatty fish, death from heart disease. But there are fish we’re better off avoiding, due to high mercury levels that can pose a health risk. This list of low mercury fish — SMASH — can help us make the healthier choices.

What is SMASH?

The acronym SMASH stands for salmon, mackerel, anchovies, sardines, and herring. These are the fish that are safest and healthiest to eat. They are nutrient-rich, high in omega-3s, and are low in mercury. Mercury is a natural element found all around us in air, water, and all living things, but in very small amounts. It makes its way into our food in several ways, including pollution. All fish have at least some mercury in them, but levels vary widely by species. Most of these levels are far below what the U.S. has deemed allowable in seafood, but large and longer-living fish — like shark, swordfish, large tuna — have the highest amounts of mercury.

Mercury risk

Most of us have at least trace amounts of mercury in our bodies. Centers for Disease Control and Prevention (CDC) data show that most of these levels are below those associated with health risk. Exposure to mercury most commonly occurs when people eat fish with high levels in their tissues and this is associated with serious health issues — high levels can be toxic.

Mercury is a neurotoxin, which means it affects the nervous system. In excess, it can impair vision, coordination, and speech, and can cause muscle weakness. Research, including a study published in a 2020 issue of the journal Biomolecules, has associated higher levels of mercury in the brains of patients with Alzheimer’s disease.

Especially at risk are women who are pregnant or nursing and young children, who should avoid fish known to have high levels of mercury. They should eat smaller fish — such as those on the SMASH list — and no more than two to three servings of fish each week to minimize exposure. (It should be noted that canned light tuna is made from smaller tuna, so it has lower levels of mercury than large tuna.) Be aware that fish that comes from other countries is not regulated by the same stringent U.S. seafood industry regulations, which could mean higher mercury levels.

Eat fish

It’s important to minimize mercury in our diet, but when it comes to eating fish, the health benefits far outweigh the small risk of mercury for most people. Eating fish on the SMASH list promotes good health and protects against many chronic diseases, including several risk factors for heart disease. These fish are also good sources of:

Omega-3s. These healthy fats are good for the heart.
Selenium. Often lacking in the diet, it helps protect against mercury toxicity.
Vitamin D. Supports immune function and bone health and protects against heart disease.

Bottom line

Most of us don’t have to worry about toxic mercury levels in our bodies, but it makes sense to minimize mercury by limiting fish to two to three servings per week, avoiding eating fish with high mercury levels, and enjoying fish on the SMASH list.