Eating fish tainted with mercury is a major health danger. This heavy metal is toxic to your nervous system, lungs, and kidneys. Mercury has been shown to cause motor dysfunction, brain damage, and even cancer.
And now another deadly disease has been linked to mercury in fish: amyotrophic lateral sclerosis, also known as ALS or Lou Gehrig’s disease—after the famed baseball player who died from it.
It’s a progressive neuromuscular disease that causes motor nerve cells in the brain to degenerate. Patients’ muscles wither. Their brain remains active, but is trapped in a body that is slowly paralyzed. Eventually, they can no longer breathe and they die.1
The disease is most common in people over 60. About 30,000 Americans are battling the dreaded condition.2
Researchers from Dartmouth College surveyed 294 ALS patients and 224 people without the disease to determine how much fish they ate. They also asked what types of fish they ate, and whether the fish was purchased from stores, eaten in restaurants, or caught fresh by the participants.3
Eating Mercury-Laden Fish Raises ALS Risk
Using a spectrometer they measured the mercury levels in toenail clippings from all participants. Toenails were used because they mercury chemically binds to them. Clippings reveal mercury exposure during the past 12 to 15 months. Previous research shows mercury levels in toenails correlate to levels in the brain.
The researchers found participants in the top 25% of fish consumption and mercury levels doubled their risk for ALS.
The researchers concluded mercury levels in participants involved “a species- and location-dependent effect.” In other words, not all fish are created equal. Some are loaded with contaminants, such as mercury, antibiotics, and carcinogenic chemicals.
But other fish are generally contaminant-free and have powerful health benefits. Oils and proteins in certain fish have been shown to boost brain and heart function, and help maintain a healthy body weight. The key is to eat the right kind of fish..
Another study found people pre-disposed to developing Alzheimer’s disease lowered their risk by 12.5% by just eating fish once per week.
Never Eat These Fish
- Imported catfish. It often contains antibiotics banned in the United States. Asian countries commonly use antibiotics to keep fish disease-free despite being raised in dirty water.
- Imported shrimp. They can contain antibiotics, chemical residues, and disease-causing germs. A Consumer Reports test found that 60% of shrimp samples tested contained dangerous bacteria. These included salmonella, E. coli, and MRSA. About 94% of shrimp sold in the U.S. is farmed in Asian countries.6
- Swordfish. This is a restaurant favorite. But swordfish is loaded with mercury.
- Chilean sea bass. It’s white, flaky texture has made it popular. But like swordfish, it contains high levels of mercury.
- Bluefin tuna. Most varieties of tuna contain some mercury, but Bluefin has the highest concentrations. It is most often served as sushi.
Other fish to avoid due to mercury content are king mackerel, orange roughy, shark, and tilefish. And steer clear of farmed eel. It often contains both carcinogens and mercury.4
Catching fish in local waters guarantees freshness—not that it will be free of contaminants. Rivers and lakes are often loaded with pollutants. Heed local advisories about mercury and other contaminants before eating fish you or someone you know catches.
The Five Best Fish You Can Eat
The best fish to eat are those low in mercury and other chemicals, but high in healthy omega-3 fatty acids. These include:
- Wild-caught salmon. Fresh, frozen, or canned versions are all among the healthiest types of fish.
- Sardines. They are low on the food chain, so they don’t accumulate mercury like predator fish.
- Anchovies. You can buy them fresh, frozen, or canned. Any type is low in mercury and high in omega-3s.
- Northern Atlantic mackerel. Unlike its cousin the king mackerel or kingfish, this mackerel is very low in mercury and still high in omega-3 fats.
- Arctic Char. This is one of the rare cases of farmed fish being healthy. Arctic char is known as iwana at sushi restaurants. It is farmed in systems that are chemical-free and usually void of diseases.