Sushi, introduced to the United States in the early 1900’s by Asian cultures has become a popular meal in the American Diet. Many choose sushi as the “healthier” fast food. Contrary to the burger and fries, sushi boasts vegetables, seaweed and fish. Consumers get high doses of vitamins, minerals, antioxidants, flavonoids, and omega-3s. In addition to these nutrients, if tuna is involved, consumers might also be consuming high amounts of Mercury.
Mercury, one of the first heavy metals discovered, has been used for centuries. Once commonplace in the medicine cabinet in the forms of medication and thermometers, the mysterious element has been discovered to cause many adverse health effects. Mercury is considered highly toxic and can cause damage to the brain, kidneys and lungs. Poisoning symptoms can range from mild sensory impairment in the form of disturbed sensation to significantly impaired cognitive skills. We have since banned mercury thermometers from our homes and hospitals, so why do we continue to expose ourselves to this harmful element by the consumption of fish?
Yes, the health benefits of fish are numerous. Fish contains omega3 fatty acids (an important fatty acid for the heart and brain), vitamins and minerals, and is a good source of lean protein. Of course, there are many factors that play into whether your fish at the dinner table contains toxic amounts of Mercury. First, not all fish are the same. Depending on what type of fish you are consuming, you might be okay. The FDA reports the fish with the most Mercury levels (parts per million) are swordfish and Tuna with 0.995 and 0.689 ppm of Mercury respectively. Salmon comes in as one of the lowest with 0.022ppm and scallops with the least of all (0.003ppm). Even at low levels, Mercury is a heavy metal which means it might deposit in the body and may linger for days, months or even years. Multiply this by many days or years and you might have a problem.
In one study done at Stony Brook Medical Center on Long Island. Of 118 patients that consumed fish, those that consumed the ones with the highest levels of mercury reported more fatigue. Also, the study found that weekly consumption of high Mercury level fish was associated with increased blood levels of Mercury ranging from 6.3-9.47 micrograms/L. 
So, the next time you go to grab your poke bowl for the 3rd time this week or your spicy tuna roll, think twice. Substitute the tuna for some lower mercury fish such as salmon and limit excessive consumption. If you have concerns of mercury levels in your body, ask your doctor to test your levels.
 Mercury Levels in Commercial Fish and Shellfish (1990-2012) https://www.fda.gov/food/foodborneillnesscontaminants/metals/ucm115644.htm
 Kothari S, Kruse D, Karimi R, et al. High mercury seafood consumption associated with fatigue at specialty medical clinics on Long Island, NY. Prev Med Rep. 2015;2:798-802. Published 2015 Sep 25. doi:10.1016/j.pmedr.2015.09.010