A study of sushi eaters in New Jersey shows just how much sushi people are eating (and who's eating it) -- as well as which kinds of sushi may expose people to the highest levels of methylmercury. Researchers from Rutgers University and the Robert Wood Johnson Medical School examined sushi consumption among 1,289 people who lived in a New Jersey university community, as well as levels of mercury among samples of sushi taken from stores and supermarkets in New Jersey, New York City and Chicago. Of the people surveyed in the study, 92 percent said they ate fish, consuming an average of five fish or sushi meals each month. Seventy-seven percent of the respondents said they ate sushi, averaging 3.27 sushi meals a month. The amount of fish in pieces of sushi consumed by the study participants ranged from 5 to 25 grams. Among the findings of the Journal of Risk Research study: - Caucasians and Asians (particularly East Asians, compared with South Asians) reported eating the most sushi.

Some people surveyed in the study reported eating more than 40 pieces of sushi a month, and eight of the people in the study said they ate fish or sushi at least once a day. - The top 10 percent of sushi-eaters exceeded the Center for Disease Control Minimal Risk Level and the WHO Provisional Tolerable Weekly Intake for methylmercury consumption. (People in this group ate sushi for an average of 30 to 60 meals each month.) - The type of sushi with the highest average levels of methylmercury was tuna sashimi (with about 0.61 parts per million of methylmercury). - Levels of mercury varied between sushi samples, "with some levels as high as 2.0 ppm [parts per million], which makes exposure to mercury from consumption of sushi (or sashimi) less predictable." - Atlantic bluefin and bigeye tuna are particularly high in methylmercury. - Eel, crab, salmon and kelp sushi had lower levels of methylmercury. "The risk communication message is becoming increasingly clear.

For people who eat fish or fish-sushi infrequently (less than monthly), the choice of which fish to eat regarding mercury content is probably not important," the researchers wrote in the study. "People who eat fish frequently, more than weekly, must choose wisely. High-end sushi eaters should minimize intake of tuna." While methylmercury is hard to avoid completely -- everybody has some amount of it in their tissues, due to its prevalence in our environment and the consumption of seafood -- it can be dangerous, depending on a number of factors (such as dose, age of exposure, and duration and route of exposure). The Environmental Protection Agency points out that methylmercury can be especially dangerous for fetuses, infants and children, as it can impair neurological development (which is why pregnant women are discouraged from eating methylmercury-containing fish and shellfish). However, the EPA also pointed out that a 1999 and 2000 report from the Centers for Disease Control and Prevention showed that most people don't have mercury levels high enough in their blood to cause health effects.

For a list of seafood that is highest and lowest in mercury, check out the Natural Resources Defense Council's list here. And if you want to see the mercury levels of your seafood while on-the-go, The New York Times reported on a smartphone app, called Safe Sushi, that indicates the mercury levels of 38 varieties of seafood. The findings on mercury levels in bigeye and bluefin tuna fall in line with a 2010 study in the journal Biology Letters, which showed that these kinds of tuna -- which are more commonly served at restaurants -- have higher levels of mercury than species you could buy at grocery stores, LiveScience reported. sushirijst onlineThat study involved using DNA barcoding to examine mercury levels among different kinds of tuna species from sushi samples taken from 54 restaurants and 15 supermarkets. sushi drift tires ebay

The researchers found in that study that yellowfin and bluefin toro (fatty tuna) had lower levels of mercury, compared with the bluefin akami and bigeye tuna. In addition, an investigation conducted by the Milwaukee-Wisconsin Journal Sentinel in 2008 examined 10 samples of sushi from three restaurants and a grocery store, and found that two of the pieces of tuna had extremely high mercury levels, while the shrimp, salmon and mackerel sushi samples had just "trace amounts" of mercury. sushi grade fish glendaleThe Journal-Sentinel's Raquel Rutledge reported:sushi grade tuna and mercury A 130-pound person who ate 8 ounces (about six to eight pieces) of either tuna sampled by P.I. [the newspaper's Public Investigator team] would exceed the U.S. Environmental Protection Agency's standard -- or suggested maximum daily intake of methyl mercury -- by more than 35 times.

It's not just sushi eaters who should be aware of mercury in fish. In 2011, Consumer Reports released an examination of mercury levels in canned tuna, showing that white, or albacore, tuna is higher in mercury than light tuna. However, all of the 42 samples tested by Consumer Reports had some level of mercury, ranging from 0.018 parts per million to 0.774 parts per million. A report released earlier this year by University of Bristol researchers showed that fish may only be responsible for 7 percent of dietary mercury in humans, TIME pointed out. In addition to fish, tea and alcohol seemed to be the next-biggest culprits for mercury contamination. The day it was discovered that tuna may contain large amounts of mercury, tuna salad sandwiches became social pariahs. Experts advised women and children to limit tuna consumption, as mercury can build up in the blood and even cause brain damage. In kids, high mercury levels can impair neurological development. You may unsubscribe at any time.

But a study published in the journal Biological Letters finds that all tuna is not created equal. While most species contain dangerous levels of mercury, some have significantly lower amounts than others. Unfortunately, learning how to select the healthiest fish and avoid the unhealthiest can be difficult, thanks to strange, sometimes absent labeling on menus and packages. THE DETAILS: The study authors worked with The New York Times to collect tuna samples from 54 sushi restaurants and 15 grocery stores in New York, New Jersey, and Colorado. In total, they collected 100 samples. Using DNA tests, they identified the exact species of tuna and, because mercury content is usually lower in tuna with a high fat content and vice versa, classified them as either lean (akami) or fatty (toro). Finally, each sample was tested for mercury content. The highest levels of mercury were found in two species, bigeye and lean bluefin (bluefin akami), and the lowest levels were in yellowfin and fatty bluefin (bluefin toro).

Every sample contained mercury at levels above those designated as safe by the Environmental Protection Agency (EPA). The researchers also found higher mercury levels than have been reported by the Food and Drug Administration (FDA), and noted that tuna sold in restaurants contained higher levels than tuna bought in grocery stores. Most likely this is because sushi-grade tuna is leaner and comes from larger fish, note the researchers. Finally, 77 percent of the tuna that came from grocery stores was yellowfin, which has relatively low mercury levels. WHAT IT MEANS: Mercury-contaminated fish remains your primary source of exposure to this brain-damaging heavy metal, according to the EPA. And predatory fish like tuna, swordfish, and sharks contain the highest levels. Mercury does the most damage to women who are either breastfeeding, pregnant or of childbearing age, since the heavy metal can affect the developing brains of fetuses and infants. The EPA and Food and Drug Administration fish-consumption advisory stipulates that these women, and their children, should avoid entirely shark, swordfish, king mackerel, and tilefish, due to high mercury levels.

The advisory also says to eat no more than two meals a week of fish or shellfish with lower levels of mercury, such as shrimp or wild Alaskan salmon. Tuna falls between those two categories, but it’s tough to know what you're eating when restaurants and grocery stores don't always advertise what species of tuna is on the menu. To help you understand what you’re eating, here's a useful breakdown of tuna terminology, courtesy of the Monterey Bay Aquarium:Albacore tuna is one of the healthiest fish you can eat, provided it's caught in the U.S. or British Columbia. This tuna is caught when it's younger and therefore has had less time to build up high levels of mercury, but albacore imported from other countries is caught when it's older and thus contains more mercury. So location is key. Canned albacore is always labeled "chunk white." You can buy American and Canadian albacore tuna from online sources including Heritage Foods USA, Pacific Fleet, MaryLu Seafoods, Wild Planet, and Wild Pacific Seafood.

Unlike "chunk white," "chunk light" tuna is a blend of different species and often includes meat from high-mercury bigeye tuna, along with less-contaminated yellowfin. It's best to avoid chunk light tuna. Instead, stock up on cans of American and Canadian albacore."Chunk light" and "canned light" aren't same thing, either. The most common type of tuna sold as "canned light" is skipjack, which is sometimes referred to as yellowfin, and contains relatively low levels of mercury. However, according to the study, yellowfin samples still had enough mercury to make them unsafe for women and children. Again, best to avoid this type of tuna in favor of American and Canadian albacore.At a sushi restaurant or in the frozen fish section, tuna is often listed under market names that refer to cuts of meat, rather than species names. Thus, bigeye and yellowfin tuna can variously go by the names ahi, maguro, or toro. Bluefin tuna is often listed by its species name, but is also sold as kuromaguro, horse mackerel, atun de aleta azul, hon maguro, and toro.