The New Complete Book of Food

 The New Complete Book of Food

have shown that women who eat lots of high-mercury fish while pregnant are more likely

to deliver babies with developmental problems. As a result, the FDA and the Environmen-

tal Protection Agency have now warned that women who may become pregnant, who are

pregnant, or who are nursing should avoid shark, swordfish, king mackerel, and tilefish,

the fish most likely to contain large amounts of methylmercury. The same prohibition

applies to very young children; although there are no studies of newborns and babies, the

young brain continues to develop after birth and the logic is that the prohibition during

pregnancy should extend into early life.

That does not mean no fish at all should be eaten during pregnancy. In fact, a 2003

report in the Journal of Epidemiology and Community Health of data from an 11,585-woman

study at the University of Bristol (England) shows that women who don’t eat any fish while

pregnant are nearly 40 percent more likely to deliver low birth-weight infants than are

women who eat about an ounce of fish a day, the equivalent of 1/3 of a small can of tuna.

One theory is that omega-3 fatty acids in the fish may increase the flow of nutrient-rich

blood through the placenta to the fetus. University of Southern California researchers say

that omega-3s may also protect some children from asthma. Their study found that children

born to asthmatic mothers who ate oily fish such as salmon at least once a month while

pregnant were less likely to develop asthma before age five than children whose asthmatic

pregnant mothers never ate oily fish.

The following table lists the estimated levels of mercury in common food fish. For the

complete list of mercury levels in fish, click onto http://www.cfsan.fda.gov/~frf/sea-mehg.html.

Mercury Levels in Common Food Fish

Low levels (0.01–0.12 ppm* average)

Anchovies, butterfish, catfish, clams, cod, crab (blue, king, snow), crawfish, croaker

(Atlantic), flounder, haddock, hake, herring, lobster (spiny/Atlantic) mackerel, mul-

let, ocean perch, oysters, pollock, salmon (canned/fresh frozen), sardines, scallops,

shad (American), shrimp, sole, squid, tilapia, trout (freshwater), tuna (canned, light),

whitefish, whiting

Mid levels (0.14–0.54 ppm* average)

Bass (saltwater), bluefish, carp, croaker (Pacific), freshwater perch, grouper, halibut,

lobster (Northern American), mackerel (Spanish), marlin, monkfish, orange roughy,

skate, snapper, tilefish (Atlantic), tuna (canned albacore, fresh/frozen), weakfish/

sea trout

High levels (0.73–1.45 ppm* average)

King mackerel, shark, swordfish, tilefish

* ppm = parts per million, i.e. parts of mercury to 1,000,000 parts fish

Source: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition,

“Mercury Levels in Commercial Fish and Shellfish.” Available online. UR L: http://www.cfsan.fda.

gov/~frf/sea-mehg.html.