You’ve likely seen warnings about the dangers of mercury in tuna. But just how big of a deal is it? Consumer Reports recently decided to find out.
When researchers at the magazine sent 42 samples of leading-brand tuna products to a lab, they found trace amounts of mercury in every single can. Now this metal is particularly dangerous for developing fetuses and children, but larger doses could cause neurological or heart problems to even a full-grown man.
In fact, the mercury levels in the tuna ranged from 0.018 to 0.774 parts per million (ppm). And while all of the samples still fell within the Food and Drug Administration’s limit of 1 ppm for what can be stocked in stores, many exceeded the Environmental Protection Agency’s more stringent 0.5 ppm safety level.
Why the disparity? Well, the jury is still out on how much mercury is truly harmless. It also depends on a person’s weight and ability to break down the metal before it builds up in the tissues. Your body processes mercury, but can only handle so much at a time.
And while Consumer Reports didn’t report which brand names had the most mercury, they did find a pattern: On average, white (or albacore) varieties contained far higher levels of mercury than the “light” tuna; 0.427 ppm versus 0.071 ppm.
“White tuna are larger fish, higher up in the food chain, so they accumulate more mercury,” explains Shawn Gerstenberger, Ph.D., chair of the environmental and occupational health department at the University of Nevada, Las Vegas, whose separate research has also warned of the widespread presence of mercury in canned tuna.
You see, mercury is present in both the environment (like volcanoes) and man-made sources (like coal-fired power plants). When these factories and natural structures release mercury, it falls from the air into streams and oceans, where it’s converted into a particularly toxic form of itself, methylmercury. From here, it’s absorbed by both fish. But the fish that are the biggest, and who have the longest lives, tend to absorb the most of it. That’s partly because they eat the smaller fish that have also absorbed mercury of their own.
But Urvashi Rangan, Ph.D., Director of Technical Policy at Consumers Union, the nonprofit publisher of Consumer Reports, points to her group’s earlier work which found that mercury levels in about 6 percent of light tuna samples spiked at least as high as white. She and her colleagues suggest that pregnant women steer clear of tuna altogether.
So how much tuna should you eat? The organization recommends that adult men stop at 5 ounces of white or 14.5 ounces of light tuna a week, based on a mercury concentration of 0.5 ppm. (A typical can of tuna contains 5 or 6 ounces, including liquid.)
Take home point: Just use a little common sense and don’t eat excessive amounts of tuna. Keep your diet diverse and switch species.
Article from MSN Health