Selecting Healthy Fish - Minimizing Mercury Exposure
Fish is one of the healthiest food you can eat, and something I often recommend as part of an anti-inflammatory/cardiometabolic eating pattern. In fact, I recommend 2-4 servings per week since fish are rich in omega-3 fats which are strongly anti-inflammatory. Unfortunately, consuming seafood is the most common way people in the US are exposed to mercury. Here’s how to reduce that exposure.
Mercury is a toxic heavy metal found in the environment and considered to be 1 of the top 10 chemicals of public health concern by the World Health Organization. Mercury exists in 3 forms: Organic (e.g. methylmercury in fish), inorganic (e.g. batteries and disinfectants), and elemental (e.g. dental amalgam and thermometers). Mercury found in the environment is transformed by bacteria into the harmful organic compound methylmercury, and all forms of mercury accumulate in the body over time.
While small amounts of mercury in seafood do not appear to pose serious health concerns for most people, pregnant women and young children may be susceptible to potential neurological development issues. Toxicity with mercury depends on the dose, exposure, frequency and overall health of the person. Symptoms can vary and may include tremors, insomnia, memory loss, headaches and cognitive dysfunction. Recent studies have also linked high exposure to heavy metals, such as mercury, to conditions like Alzheimer’s, Parkinson’s, autism, depression and anxiety.
Seawater contains only small concentrations of methylmercury, but sea plants like algae absorb it. Fish then eat the algae, absorbing and retaining its mercury. Nearly all fish and shellfish absorb and accumulate methylmercury, but larger, longer living fish (such as swordfish and bigeye tuna) tend to eat many smaller fish, which contain small amounts of mercury. They accumulate the highest levels of mercury, up to 10 times higher than the fish they consume. This process is known as biomagnification. These fish pose the greatest risk and should be avoided. Other fish that should be avoided due to high levels of mercury (greater than 0.46 mcg/g) include shark, king mackerel, marlin, tilefish and orange roughy.
The health benefits of fish, however, outweigh the risks from mercury exposure - so long as you moderate your consumption of high-mercury fish and mostly select fish that are low in mercury. According to the US Environmental Protection Agency or EPA, “best choices” for fish with low levels of mercury (< 0.15 mcg/g) include salmon (especially wild Alaskan), black cod, haddock, sardines, flounder, shrimp, scallops, catfish and canned light tuna - which are good sources for health-protective omega-3 fatty acids. Adults should eat 2 to 3 servings per week of these fish.
“Good choices” for fish with a little higher level of mercury (0.15 mcg/g up to 0.46 mcg/g) include yellowfin and white albacore tuna, Chilean seabass, grouper, halibut, Mahi Mahi, monkfish and snapper. A single serving of fish in the “good choices” category can be enjoyed once per week.
The Bottom Line
Overall, you should not be afraid of eating fish. Fish are an important source of omega-3 fatty acids and provide multiple other benefits.
It is generally recommended that most people eat two to four servings of fish per week. The Food and Drug Administration (FDA) does advise people at high risk of mercury toxicity, such as pregnant or breastfeeding women and children, to keep the following recommendations in mind (FDA - Eating Fish: What Pregnant Women and Parents Should Know):
Eat 2–3 servings (227–340 grams) of a variety of fish every week.
Choose lower-mercury fish and seafood, such as salmon, shrimp, cod, and sardines.
Avoid higher-mercury fish, such as bigeye tuna, tilefish, shark, swordfish, and king mackerel.
Following these tips will help you maximize the benefits of eating fish while minimizing your risks of mercury exposure.
Here are a few of our favorite recipes using “best choice” seafood/fish - enjoy!
