The Catch of the Day
Understand your fish mercury levels.
When it comes to mercury levels, all fish are not created equal.
Fish and seafood are an important part of a healthy diet. Rich in omegas, DHA, and heart-healthy lean protein, including fish into your diet is an excellent way to improve your overall health. So, what’s the catch (pardon the pun)? There are two broad arguments for taking careful stock of how much fish you eat: the environmental concerns with respect to overfishing, and separately, the health concerns around mercury levels. Although recent research is beginning to tie the two issues together, this short piece is concerned primarily with the latter.
When we are traveling and visiting great restaurants around the world, it’s common to see exotic fish species on the menu, often prepared in enticing fashion that may exceed our typical at home practices. It’s logical that we want to experience fish as those wonderful chefs would have us enjoy it. Yet, it’s also important to bear in mind that some of the fish varieties that come with the highest price tags beside them sometimes also come with the highest mercury levels.
Mercury is a Neurotoxic Substance
Mercury is a neurotoxic substance and too much of it can be extremely harmful to your health. One of the most famous stories of mercury toxicity is Tony Robbins, who began adding fish to his long-standing plant-based diet. He consumed relatively large quantities of swordfish and tuna, which ultimately raised his mercury levels to the point where he began experiencing fatigue and other cognitive issues. Fortunately, it was recognized quickly and Tony was able to clean his body of mercury and reverse the effects.
The CEO of Imax Corp, Richard Gelfond, loved sushi and ate it twice a day for two decades. He began experiencing mobility and balance issues and fatigue. After some time, it was discovered he had 14 times the level at which one would normally be classified with mercury poisoning. Today, Mr. Gelfond walks with a cane, due to permanent nerve damage. To help increase knowledge around mercury, Mr. Gelford funded a research program.
There are two types of mercury that can create toxicity. The kind that is found in fish is called Methylmercury and is organic. Inorganic mercury, like those classified as environmental toxins (and perhaps some of your silver teeth fillings) can be even more toxic.
Historically, environmental toxins were sometimes used in manufacturing. Famously, hat-makers often used mercury and many experienced cognitive impairments due to mercury poisoning — the likely inspiration for Alice in Wonderland’s Mad Hatter.
Common symptoms of mercury poisoning include fatigue, memory problems, joint pain, and mobility issues.
A study done in New York City showed that 50% of Asians and 25% of all adults had mercury levels that exceeded the maximum recommended. A similar study in Florida indicated that half the subject population had mercury levels higher than the EPA guidelines.
However, it is children and unborn infants who are most susceptible to mercury toxicity, because of their rapidly developing brains.
Why Fish?
The saying “dog eat dog” is meant to characterize a viscously competitive world. Yet, in reality pack animals do not routinely eat each other — on a daily basis anyway. That is unlike our fish friends, many of whom seem to simply swim around looking for other fish to eat. Watching a nature show about sea life seems to distill down to fish trying to eat other fish while watching that they themselves are not eaten. The bigger fish eat the smaller fish and so on.
When a fish consumes another fish it adds a bit more mercury to its own system. It stands to reason that large predatory fish have high levels of mercury (pound for pound) than smaller fish species.
As one might suspect, mercury enters the fish population at the bottom of the food chain, with zooplankton. As one climbs the food chain, each predator has slightly more mercury than the one below. The process is called biomagnification.
Credit: Georgia Dolphin Ecology Program
The above diagram is a useful tool for understanding how much mercury is in various fish species. Next time you order in a restaurant, refer to this mercury wheel. Many times, some of the most desirable fish dishes on the menu can be of very high mercury. Typically, large predatory fish who live a long life, and hence have substantial opportunity to accumulate mercury stores, have the highest levels, and should be avoided on the menu.
It’s important to note that not all fish “types” are the same. For example, if you love salads with tuna on top, you can opt for a tuna species that has less mercury than another type of tuna.
Being informed is the key. Fish remains a fantastic food choice and is one of the typical food choices in a heart-healthy Mediterranean or pescatarian diet. But, remember that you tend to hold on to mercury. So, if you eat a lot of fish, it’s all the more reason to pick fish species that possess the lowest levels of mercury, so you can continue to enjoy your healthy diet, free from worry.
If you suspect mercury toxicity?
If, like many people, you’ve eaten high-mercury fish species for years and haven’t given mercury much thought — and you’re feeling any of the classic symptoms of mercury toxicity, speak to your doctor. Testing for mercury levels is fairly straightforward and simple. Be aware that there are different medical opinions on how best to detoxify your system based on how effective you are at excreting the toxins. Again, seek sound medical advice from a doctor.
This article does not constitute medical advice. Always seek the opinion of a medical professional before starting a nutrition or fitness program.