What You Need to Know About Eating Fish
With concerns about mercury levels in fish -- a usually healthful food, how much fish should pregnant women eat? What other options provide the same health benefits as fish? Follow these guidelines to stay healthy.
Undisputed Benefits of Omega-3 Fats
The omega-3 fats in many fish and seafood are known to lower risk of heart
disease and benefit the brain. The American Heart Association advises at least
two servings a week of fish like mackerel, lake trout, herring, sardines,
albacore tuna, and salmon because of these healthy fats. However, the following
people should take care to consume fish sources of omega-3 fats with lower
mercury content: women who wish to become pregnant or are now pregnant; women
who are nursing; and young children.
In a developing fetus, omega-3 fats promote brain, eye, and motor
development, the EPA notes.
Pregnant Women and Big Fish Risks
The mercury in fish and seafood is indeed the big concern -- although there
are other toxins like PCBs that have warranted some worry. Mercury exists
naturally in the environment, but more is released into air, land, and water by
trash burning, fossil fuel combustion in factories, mining, and the dumping of
sewage sludge in croplands.
Once mercury gets into surface water, it quickly makes its way through the
aquatic food chain. In smaller organisms, there is usually an insignificant
amount of mercury. But as fish get older or as bigger fish eat smaller ones,
the mercury content begins to build.
Fish at the top of the food chain - pike, bass, older or large tuna,
tilefish, king mackerel, shark, and swordfish - tend to have higher levels of
mercury, from one to 1 million times greater than the amount in the waters,
according to the EPA.
If you're eating a lot of fish, mercury accumulates in your bloodstream over
time. While the body naturally gets rid of mercury, it may take a year for the
levels to drop significantly. Thus, it may be present in a woman even before
she becomes pregnant. This is the reason why women who are trying to become
pregnant - or pregnant women -- should also avoid eating certain types of
For women wanting to switch to other omega-3 sources, there are options,
says Julie Redfern, RD, a registered dietitian in obstetrics at Brigham &
Women's Hospital in Boston. She has counseled thousands of pregnant or
"It's one of those questions that comes up almost every day … mercury
and fish," Redfern tells WebMD. "Some women are very well-read, and
they say they are not going to eat any fish. Others say, 'I love fish,' and
want to know what's safe. I give them the FDA's list of safe fish. I ask them
what fish they usually eat, and look for it on the list. I also talk to them
about canned tuna, about the different kinds of tuna - and what's on the
Overall, she says, "I feel very comfortable reassuring them that if they
keep it to the 'safe' fish -- and eat no more than two servings a week --
they'll be fine."