This post originally appeared on Sightline Institute's blog.

To eat fish, or not? If you're pregnant, nursing, or even thinking about becoming pregnant, it's a Catch-22. Seafood is the best possible source of the long-chain omega-3 fatty acid DHA, which is critical for a baby's brain and eye development, both in utero and in the "fourth trimester," while the baby is nursing and the brain is still developing. But there's a catch: seafood contains contaminants that can be harmful to babies---particularly methylmercury, which can harm the developing nervous system, causing subtle deficits in language, memory, motor skills, perception, and behavior.

So for a pregnant woman, the decision whether to eat fish is now freighted with consequences. Eat fish, and you're putting your baby's brain at risk of from toxic contaminants. Skip fish, and you're denying your baby's brain of crucial nourishment.

Pregnant and nursing women never asked to make this choice.

Mercury is everywhere, even in the air we breathe. It comes from a variety of sources, but the largest in the US are coal-fired power plants, which exhale elemental mercury in the fumes of coal smoke. The mercury drifts around on air currents, and eventually settles into water bodies, where bacteria convert it into a far more troublesome form called methylmercury. Methylmercury binds to protein, and accumulates in every-higher concentrations at every step of the food chain. It's poison. It hurts babies' brains. All fish contain some methylmercury, and some fish species contain enough that doctors recommend that expectant mothers avoid eating them completely.

And that's a shame, since there's s no better source of DHAs than fish. DHAs build brain connectors while a baby's body is developing in the womb.

So, there, in a nutshell, is the dilemma. As a community, we've allowed one of the most healthful foods for pregnant mothers to become contaminated with a compound that can harm developing babies' nervous systems. We've given polluters free rein; but left the tough choices to women, and the hardships to the children they bring into the world.

What's the right choice for an expecting mother? Well, as a fisherman's daughter, a former Puget Sound gillnetter myself, and proud resident of "Salmon Nation," I believe in the power of fish---particularly salmon---as a super food. And the more I read, the more I believe it's also super brain food. My favorite book about nutrition during pregnancy and early childhood, Nina Planck's Real Food for Mother and Baby, goes so far as to say that your baby's brain is "made of fish."

But that decision---"Yes, I'll eat fish"---prompts one question more: How much fish is safe?

Well, it depends on the type of fish. The Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) officially advise women who "may become pregnant, pregnant women, nursing mothers, and young children" to limit consumption certain fish and shellfish to 12 ounces a week, and to avoid shark, swordfish, king mackerel, and Tilefish completely. (Drat---I've always loved swordfish!) EPA says that, and I quote: "By following these recommendations for selecting and eating fish or shellfish, women and young children will receive the benefits of eating fish and shellfish and be confident that they have reduced their exposure to the harmful effects of mercury." In addiiton, each state has its own advisories about fish consumption as well.

Generally speaking, the fish to avoid are large predators. Peak predators act as concentrators for bioaccumulative toxics: their bodies absorb the methylmercury from their prey, which, in turn, have absorbed methylmercury from living things lower on the food chain. And the bigger the predator fish, the more fish it eats. Larger fish also tend to live longer than smaller fish, so there's simply more time for mercury to build up in their bodies.

But just as some fish contain high levels of mercury, others contain less. Five of the most commonly eaten fish that are considered "low in mercury" are shrimp, canned light tuna, salmon, pollock, and catfish. Albacore ("white") tuna, another commonly eaten fish, has more mercury than canned light tuna. So when choosing your two meals of fish and shellfish per week, the EPA/FDA recommendations suggest you limit yourself to up to 6 ounces (one average meal) of albacore tuna per week.

But how confident can you be, really, that fish are actually a healthy, safe food for you and your kids?

Studies are mixed. Planck points to a few that indicate more fish is better. In 2005, researchers at the Harvard School of Public Health announced that the government mercury warnings could cause pregnant women to eat too little fish to nourish her baby's brain. In 2007, Joseph Hibbeln, an expert on omega-3 fats at the National Institutes of Health, published a study of more than eleven thousand pregnant women near Bristol, England. The women consumed varying degrees of seafood each week: none at all, around the recommended portions, or more than 12 ounces (at least 3 servings a week.) Researchers later assessed the women's children, aged six months to eight years, for various measures of mental and social development. Even after accounting for about two dozen confounding factors---social disadvantage, perinatal health, diet, etc.---the children of women eating less than two servings of fish per week had lower verbal, fine motor, and social skills than the children of the fish-eating mothers. The lower the seafood intake, the higher the chances of poor development. Some health researchers have even begun to wonder whether fish oils might even protect against toxic methylmercury.

Biologist Sandra Steingraber in her book Having Faith, An Ecologist's Journey to Motherhood, on the other hand, cites a bunch of studies that strike fear in any mother-to-be. A study in the Faroe Islands, for example, carried out by Danish researcher Philippe Grandjean, looked at 1,022 babies born in 1986-87 to women who ate fish and high-mercury content whale meat while pregnant. When they were seven years old, the children were evaluated on their cognitive and motor skills. The results were sobering. Deficiencies were found in memory, learning and attention that were proportional to the level of mercury that had been recorded in their umbilical cord blood and maternal hair. "These children were not actually sick. They were just slower in solving riddles and other puzzles." In the 1970s, a group of mothers in Iraq unknowingly ate flour milled from mercury-dressed wheat. At high concentration levels of mercury, their children developed progressive retardation and paralysis.

In 2000, the National Academy of Sciences released a report that concl
uded that each year in the United States, as many as 60,000 children are born at risk for neurodevelopmental problems owing to prenatal exposure to mercury---these are kids that the report described as "struggling to keep up in school and who might require remedial classes or special education."

Steingraber points out that "Big Fish"---fisheries industry lobbies equivalent to "Big Oil"---have stood side-by-side with utility companies to fight tighter standards for mercury. If this kind of pressure wins out, it means that levels of the metal could keep rising to the point where the choice would be all too clear: forego brain-nurturing fish altogether. (As I mentioned recently, the US has taken some baby steps towards curbing mercury pollution.)

In my own deliberations, I've erred on the side of fish. Seafood is simply the best way to get the DHA my baby needs. Salmon is among the safer seafood choices and it's a personal favorite. A 3.5-ounce portion of wild sockeye salmon contains more than 1,200 milligrams of omega-3 fats---and it's a yummy delivery system. I've eaten it a couple times a week during my pregnancy and now that I'm in the heavy-duty brain-development stage (third trimester), I'm trying to eat even more. And even though every bite (while delicious) reminds me of the serious consequences I'm toying with, I will continue to do so when I start breastfeeding.

That's the gamble I'm taking with my own baby. I'll also continue to work toward climate and energy policy that frees us from the shackles of dirty energy---because the pollution from coal plants not only threatens the climate, but byproducts like mercury are also hurting all our kids.

What's your fish story? Did you eat fish during pregnancy? And how did you sort out all the conflicting information? What can moms do to insist on better standards for mercury pollution?

Boat photo courtesy of Flickr user J.G. in S.F. under a Creative Commons license.

Sign photo courtesy of Flickr user Manuel W under a Creative Commons license.