Canned Fish


To determine whether canned fish is safe to eat, specifically regarding mercury levels in farmed fish versus wild-caught fish.

Early Findings

Mercury Accumulation in Fish

  • Mercury is a heavy metal that is found naturally in the environment. It can also be released into the environment through industrial processes and volcanic eruptions.
  • In general, fish and shellfish absorb mercury in lakes, rivers, streams, and oceans due natural concentrations in the water, as well as water pollution. Ocean water has lower levels of mercury, however, algae and other plants in the ocean absorb what mercury is in the water and these plants are then eaten by fish.
  • Mercury is not easily excreted, and overtime, through bioaccumulation, the mercury concentration becomes methylmercury, a highly toxic organic form that may cause health problems at certain levels in the human body.
  • Mercury levels may vary by the species of fish and the amount of water pollution in their environment. In addition, since larger fish tend to eat smaller fish and mercury is not easily excreted, bigger and older fish tend to have higher concentrations of mercury in their systems. This process is known as biomagnification.
  • Farm-raised fish are typically raised in tanks and/or pens located in rivers, lakes, or oceans. Therefore, they have the same exposure to mercury as wild-caught fish.

Health Effects of Mercury Poisoning

  • A study published by the Journal of Preventative Medicine and Public Health reported that about 75% to 90% of organic mercury found in fish is methylmercury and about 80% to 90% of organic mercury in the human body comes from eating fish.
  • High levels of mercury exposure has been linked with brain issues including a decrease in motor skills, memory retention, dexterity, and attention span.
  • It has also been linked to diseases such as Alzeihemer's, Parkinson's, Autism, Lupus, and Amyotrophic lateral sclerosis.
  • Mercury exposure has also been linked to an increased risk of heart attacks, LDL cholesterol, and high blood pressure.
  • Due to high-levels of zinc, protein, DHA, omega-fatty acids, iron, and zinc found in fish, women who are pregnant or breastfeeding and young children should consume fish on a regular basis. However, this population is also at a higher risk of health related issues due to high levels of mercury consumption. Therefore, this population should avoid high mercury level fish such as shark, swordfish, king mackerel and tile fish.

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