Humans are the worst. We've taken what should be the healthiest source of protein on the planet – fish – and bollixed it up.
Our factories have spewed and continue to spew (albeit a bit less than before, thanks to regulation) mercury residue into the air. It then floats down onto lakes, streams, and rivers, much of it ultimately flowing into the ocean.
There, industrious bacteria convert it into the more easily absorbed methylmercury and it's sopped up by aquatic organisms. The aforementioned beasties are then eaten by wee fish, which get gulped down by bigger fish that are in turn eaten by even bigger fish.
Big fish eat little fish in the ocean and the bay
Big fish eat little fish every night and every day
Big fish eat little fish that's what they say
But I hope the little fish get away...
These aquatic big boys are then caught and eaten by even bigger fish eaters – humans. It's the circle of life, or at least the circle of Long John Silver's.
The joke's on us, though, because the mercury gets more concentrated as you go up the food chain. Of course, even if we stick to eating the little fish, but eat them often enough, we're still screwed – the results are the same as eating the occasional portion of some of the bigger fish.
While high blood levels of mercury are of course dangerous to the nerve cells of gestating babies and young children, they're none too good for adults, either. A build-up of mercury can cause permanent damage to the kidneys and brain. Early symptoms might include lethargy, mental fogginess, muscle pain, muscle twitches, insomnia, digestive problems, and depression and/or anxiety.
And you know those occasional studies that show that a diet heavy in fish didn't have any positive effects on the cardiovascular system? It might be because of the mercury that was part and parcel of the fish that were eaten.
The easiest way to avoid this mercury is to avoid the fishes that contain the highest levels and to limit the total servings of any ocean and fresh water fish you eat per week. The second easiest way to combat mercury in fish and help turn it back into the healthy food it once was, according to research, is to simply drink a cup of black or green tea with your fishy meal.
What They Did and What They Found
Researchers at Purdue constructed a working model of the human digestive system, complete with all the enzymes and digestive juices native to real human beings. They also lined this artificial digestive tract with real human gut cells. They then tested various foods to see if they inhibited the conversion of mercury into an absorbable form.
Various concentrations of the black tea and green powders (31 to 2000 mg.) reduced mercury bioaccessibility by 88-91% and 82 to 92%, respectively. Wheat bran and oat bran did an okay job, too, with wheat bran reducing bioaccessibility by 84% and oat bran reducing it by 59-75%.
How to Use This Info
Remember that smaller fish contain less mercury. Representatives of this class include salmon, sardines, flounder, haddock, trout, and tilapia, along with a few other non-fish marine organisms like shrimp and squid.
Moderate-mercury fish, which are, as you might guess, usually bigger than the low mercury fish, include bass, halibut, mahi mahi, snapper, and tuna (chunk light), along with lobster, which of course is not a fish but a crustacean.
The biggest repositories of mercury are the monster-ish fish like grouper, sea bass, and ocean perch. The absolute worst, though, the "hateful six," are the following:
- King mackerel
- Orange roughy (which are now a threatened species)
- Tuna (bigeye and ahi)
Clearly, it's best to limit consumption of the mercury heavy hitters, but if you do perchance eat them, or eat any of the species listed in this article (and probably any organisms from the sea), it seems smart to wash them down with a cup of black or green tea.
To add another layer of protection, include a slice of whole wheat bread with your fish and tea.
And, of course, if you just want the omega-3 fatty acid benefits of fish, you can always supplement with something like Flameout®.
- Soon Mi-Shim, et al. "Impact of phytochemical-rich foods on bioaccessibility of mercury from fish," Food Chemistry, 1 January 2009.
- Mark Stibich, PhD, "Know Mercury Levels to Choose Safer Seafood," VeryWell Fit, January 25, 2021.