Science has flip-flopped on coffee, on eggs, on carbs, on salt. It's the kind of maddening confusion that makes consumers distrust everything they hear.
So perhaps we shouldn't be surprised to see the debate continuing over how much tuna, and what kind of tuna, we can eat.
Or, more precisely: how much and what kind of tuna pregnant women can eat. The concern is methylmercury, which can impair brain development in a fetus. Even adults who have too much can be affected.
The latest advice comes from Consumer Reports, which has concluded that pregnant women shouldn't eat any tuna at all.
Not even the canned light tuna the federal government says is OK.
Oddly enough, in reaching their conclusions, the food-safety experts at the nonprofit consumer group analyzed the same data as government researchers: U.S. Food and Drug Administration statistics on mercury levels in various types of seafood.
In June, the FDA and the U.S. Environmental Protection Agency declared that women and children weren't getting enough seafood. Absent mercury, fish is good for brain development and can boost a child's IQ.
So the two agencies issued a draft update of their fish-consumption advice, for the first time recommending a minimum - 8 to 12 ounces a week.
On their list of fish lower in mercury: salmon, pollock, shrimp, tilapia, catfish, cod, and - canned light tuna.
They said to avoid tilefish from the Gulf of Mexico, shark, swordfish, and king mackerel. They also advised limiting albacore tuna to six ounces a week.
After the June announcement, other groups disputed the assertion that canned light tuna was safe to eat.
Critics also contended that the agencies did not go far enough in steering consumers toward fish not only low in mercury, but also high in beneficial omega-3 fatty acids. Simply telling people to "eat more fish" didn't cut it.
The nonprofit Environmental Working Group published a chart showing these "healthier choices," including herring, mackerel, anchovy, rainbow trout, crab, and sardines.
Meanwhile, Consumer Reports went back into the data, looking not only at average levels of mercury, but also at spikes in certain cans.
Sorry, Charlie, but about 20 percent of the cans of light tuna were spiking.
"We want women to eat fish, we want them to eat plenty of it," said Urvashi Rangan, a toxicologist from Johns Hopkins University who is Consumer Reports' director of consumer safety and sustainability. But "we want them to eat the fish with the least amount of mercury, especially when they're pregnant. . . . Why not take the precaution?"
The National Fisheries Institute immediately castigated the Consumer Reports advice, contending that the focus on mercury is "disproportionate."
Noting that Consumer Reports might want to stick to reviews of stereo equipment, the industry- funded institute said the advice "flies in the face of more than a decade of independent, peer-reviewed, published science," showing the "net benefit" of eating seafood.
Rangan argues that the supposed net benefit "doesn't reduce people's exposure. . . . It doesn't actually take the mercury away."
Rangan thinks people are sophisticated enough to make wise choices, not to skip seafood altogether.
Consumer Reports recommends 17 low-mercury fish people can choose - on www.consumerreports.org now, and as part of a four-page spread in the magazine due on newsstands Tuesday. They identify the lowest-mercury fish as wild and Alaska salmon, shrimp, tilapia, scallops, oysters, squid, and sardines.
"We believe you can get your fish without so much mercury, and if you're pregnant you should take extra care to do that," Rangan said.
Notice how sardines keep making the list of beneficial seafood?
That's fortunate for Doug O'Malley's 20-month-old daughter, Elsa.
"As a parent, you are always worried about what you're feeding your young infant," said O'Malley, director of the nonprofit advocacy group Environment New Jersey. He and his wife, who got tested for mercury when she was pregnant, are "very cognizant of the danger of the pollutants in our atmosphere and our food."
It turns out Elsa has a particular fondness for a family staple: high-protein, high omega-3 sardines. Being low on the food chain, they're also low in toxins, O'Malley said.
Elsa's parents put olive oil and lemon juice on the tiny fish, "and she just gobbles them down."
GreenSpace: Mercury Levels in Fish
Here are some low-mercury fish that people should eat frequently.
A 132-pound person can safely eat 36 ounces per week. A 44-pound child can safely eat 18 ounces per week.
Wild and Alaska salmon (canned or fresh)
Shrimp (most wild and U.S. farmed)
A 132-pound person can safely eat up to 18 ounces pr week. A 44-pound child can safely eat up to 6 ounches per week.
Flounder and sole (flatfish)
SOURCE: Consumer Reports
"GreenSpace," about the environment and health, appears every other week, alternating with Art Carey's "Well Being" column.