Nutrition

Tuna and Mercury | What Do You Need To Know?

Tuna and Mercury | What Do You Need To Know?

There are two types of people in this world, those who enjoy tuna, and those who would be happy to never smell the fish again. More than likely if your goals are centered around getting bigger, leaner and/or stronger you are in the former group, and this article is for you.

Most of us know by now that tuna fish contains a type of heavy metal known as mercury, but that’s where the common knowledge on the subject usually ends. How much mercury can we safely eat through food sources? Are some individuals more susceptible to mercury poisoning than others? Are there other seafood alternatives with as many health benefits as tuna? All these questions and more will be answered in this article.


Mercury in Tuna

We’ve known about the presence of mercury in fish for over 60 years, going back to Japan during the 1950s. In a town called Minamata, those living there noticed strange behaviors in their animals. Cats would tremor nervously and birds would fall from the sky and die. Over the next few years the fish that made up a good portion of their diet were also exhibiting symptoms.

Finally in 1956 after numerous individuals in the town began showing signs of delusions and madness fishing was banned indefinitely. After an investigation on a major chemical corporation nearby was completed, it was discovered that they were dumping a large amount of heavy metal waste into the ocean. It was estimated that over 5,000 people died from mercury poisoning and over ten times as many were poisoned to some extent.

Mercury Levels in Tuna

Better known as methylmercury when present in fish, this heavy metal is absorbed by all ocean dwelling creatures, big and small. But through a process known as biomagnification, where the concentration of methylmercury rises alongside the food chain, larger fish have become the biggest threat to us. For exampl,e if a sardine has 0.010 PPM (parts per million) of mercury in its body, and every time a mackerel eats a sardine it is increasing the amount in its body by that much over time, and after eating hundreds of smaller fish the mackerel has a much larger amount of mercury in its body gram for gram compared to the sardine. This increases quickly as the bigger the fish, the more small fish it needs to survive. Which ultimately means fish such as tuna, marlin, shark and swordfish, which weigh several hundred pounds can have as much as 0.5 to 0.9 PPM. With one fish known as the tile fish native to the Gulf of Mexico having as much as 1.45 PPM.

While these numbers don’t seem like much, they are more important than you think, with less than a gram of mercury being lethal in the human body. By blocking blood vessels the compound can cause permanent damage to the central nervous system, kidneys, lungs and even the brain. Symptoms of mercury toxicity can be very subtle, in the form of a constant itching, burning, or a sensation of something crawling under your skin. More severe symptoms range from skin discoloration, peeling of the skin and fingernails, hair loss, sensitivity to light, kidney dysfunction, memory loss as well as other neurological problems, and even the growth of cancerous tumors. Most of these symptoms are reversible if caught early, but long term exposure can do irreversible damage especially to young children.

tuna and mercury


Should We Be Concerned About Eating Tuna?

At this point if you didn’t know all the negative connotations associated with mercury poisoning, you are probably hesitant to eat any seafood. But before you make any decisions let’s weigh the options as well as the pros/cons.

With tuna varying quite a bit on the PPM scale, from about 0.150 in skipjack, 0.311 in yellowfin, 0.388 in albacore, and 0.560 in bigeye, this gives you some options to still be able to eat tuna depending on how often you usually consume the fish and what type. The Center for Disease Control states a 200 pound male can eat 0.0003 mg/kg of mercury daily with no adverse side effects, which equates to about four ounces or one can of albacore or yellowtail a day (or two cans of skipjack/one can of bigeye every other day). While a 100 pound female should consume about half that amount, so about three cans of yellowfin or albacore a week. Controversy can be found in these guidelines though, as the Food and Drug Administration recommends consuming half what the CDC recommends, at three cans of yellowfin or albacore a week for a 200 pound male.

This is where personal preference and figuring out what’s best for you comes into play because there is no definitive line on when tuna shifts from a super food to a possible killer. If you are under 18 I would recommend sticking with two servings or less per week, as your body is still going through some drastic changes. Woman with small builds should stick to similar guidelines as the less you weigh the easier it is to poison your body. Pregnant woman and children should stay away from tuna all together besides an occasional serving of skipjack, as they are extremely susceptible to toxicity at relatively low levels.

Finally for adult men, you are able to eat the most amount of tuna without being affected. More than likely a serving a day will cause no negative side effects as many famous bodybuilders can attest to eating tuna daily for years without any problems.

tuna and mercury


Take Home Message

There is no doubt we should all be eating fish on a weekly basis, the amount of vitamins, minerals, protein, potassium, Omega-3 fatty acids and more shouldn’t be overlooked because of mercury. But of course there are always alternatives if you don’t enjoy fish or are in the few groups of individuals who shouldn’t be consuming tuna.

Fish oil pills can make up for a lack of Omega-3 in your diet if you don’t enjoy any type of seafood. There are many smaller fish with just as many health benefits as tuna, but without the risk of mercury toxicity including salmon, sardines, tilapia, anchovies, pollock, catfish and more. At the end of the day it comes down to your preference as well as to which food regulator you wish to follow whether it be the FDA or the CDC. I armed you with the knowledge, now go out and use it!

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Billy Galipeault

Billy Galipeault

Writer and expert


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