In a study recently published in the journal Society of Environmental Toxicology and Chemistry researchers questioned college students about their tuna consumption and their knowledge of possible mercury toxicity from eating too much of the tuna. Hair samples measuring mercury levels were taken.
High levels of methylmercury are capable of crossing the blood-brain-barrier and can affect not only cognitive function, but can affect cerebral development (especially in infants and children). Tuna contains methylmercury which is a substance that can accumulate in the body.
Symptoms of mercury poisoning include:
- Mood swings/irritability, overly emotional, etc.
- Tremors/muscle twitching
- Decreased cognitive function
Diseases/Disorders associated with mercury toxicity:
- Anxiety/Depressive disorders
Inorganic mercury compounds are released into the atmosphere from natural sources like volcanoes, fossil fuels, mining, etc. Some of these compounds settle into the ocean where they get converted into methylmercury. Sea creatures, like fish, naturally absorb these substances and this is how we are exposed to methylmercury. One of the most common exposures to mercury remains amalgam fillings, but we’ll save that article for another day.
54% of students surveyed reported eating tuna at least 3x/week. This could potentially exceed the maximum dose of methylmercury deemed safe by the EPA. 7% of the students reported eating more than 20 tuna meals each week! Hair analysis measuring mercury found that some of these students’ mercury levels were above what is considered a level of concern.
How much fish should I be eating?
The EPA has created guidelines to prevent you from being exposed to too many heavy metals. Following these recommendations will reduce your risk. Eating wild caught, not farm raised will also help to reduce these risks. Watch for labels like “Atlantic Salmon” if it doesn’t specifically say “wild caught” then it was farm-raised.
For an adult, 1 serving = 4oz which is about the size of the palm of your hand. Adults should eat 2-3 servings of the “best choice” fish each week. For children, 1 serving = 1oz at age 2 and increases with age to 4oz by age 11.
The answer is YES continue to eat fish! A diet high in fish can help to reduce your risk of cardiovascular disease, improve cholesterol levels (increasing the good HDL, and decreasing the bad LDL), and has been shown to decrease inflammation. Limit your tuna consumption, and follow the recommended guidelines provided in the chart below.
Tonight I’m grilling salmon and asparagus, topped with blended basil and olive oil with a side of couscous. Is it dinner time yet???
- Bernhoft RA. Mercury toxicity and treatment: a review of the literature. J Environ Public Health. 2012.
- Murata Y, Finkelstein DB, Lamborg CH, Finkelstein ME. Tuna consumption, mercury exposure, and knowledge about mercury exposure risk from tuna consumption in university students. Environmental Toxicology and Chemistry. 2019.
- Patrick Houssard et al. A Model of Mercury Distribution in Tuna from the Western and Central Pacific Ocean: Influence of Physiology, Ecology and Environmental Factors. Environmental Science & Technology, 2019
- Raphael A. Lavoie, Ariane Bouffard, Roxane Maranger, Marc Amyot. Mercury transport and human exposure from global marine fisheries. Scientific Reports, 2018; 8 (1)