Mom’s Exposure to Mercury Linked to Kids’ ADHD Symptoms

Aside from occupational exposure, most people are exposed to mercury by eating fish — yet eating fish is good for moms and babies. So, what are pregnant women to do?

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The health risks of mercury exposure are well documented, and the harms for still-developing fetuses are particularly concerning. Now, the latest study finds that kids who were exposed to more mercury in the womb were more likely to show problems with attention and hyperactivity and other symptoms of ADHD at age 8.

Complicating the matter, however, is that the same study found that children whose mothers ate more fish during pregnancy — fish is known to be a main source of mercury exposure for many people — had a significantly lower risk of ADHD symptoms than kids whose mothers ate less fish. The finding raises the possibility that the health benefits of eating fish, which is rich in the omega-3 fatty acids that are good for brain development, could outweigh the harms of low-level mercury exposure.

Previous studies attempting to define the risk of low-level exposure to mercury have been inconclusive: one large study showed that school-age children who were exposed to higher levels of mercury in utero — as measured by samples of their cord blood — showed more errors and lower scores on neurocognitive tests. But another study indicated that children exposed to higher levels of mercury were actually less likely to show problem behaviors such as hyperactivity or chronic inattention.

(MORE: Consumer Reports Warns Pregnant Women Against Canned Tuna)

So Dr. Susan Korrick and her colleagues at Brigham and Women’s Hospital in Boston studied data on 788 infants born between 1993 and 1998 in the New Bedford, Mass., area. The researchers measured the mercury in the children’s mothers’ hair samples 10 days postpartum, and used a 59-item questionnaire to evaluate the children’s behavior at age 8.

The researchers found that higher mercury levels in the hair samples were associated with a greater risk of symptoms of ADHD, or attention deficit-hyperactivity disorder in children (the researchers did not confirm ADHD diagnosis, but only determined whether the children had symptoms that were typical of the disorder). Even after adjusting for potential factors that could influence the risk of ADHD symptoms, including the mother’s education or depression, or her diet while pregnant, the correlation with mercury remained.

Studies hint that mercury affects central nervous system development by disrupting levels of important neurochemicals such as dopamine.

(MORE: The Heart Benefits of Fish May Outweigh the Mercury Risks)

“The message that prenatal mercury exposure is not healthy for the fetus is not changed by this study,” says Korrick. But because those studies have been inconsistent, Korrick says the results should “demonstrate fairly consistent findings related to ADHD behaviors.”

Based on the new data, Korrick says that the higher risk of ADHD symptoms starts to appear at mercury levels of 1 microgram per gram: rates of inattention and hyperactivity among kids whose mothers showed levels of exposure above that threshold ranged 40% to 70% higher than for those whose mothers had lower levels of mercury.

But that study doesn’t suggest that pregnant women should avoid eating fish altogether. The data also showed that children of women who ate more fish during pregnancy — more than two servings a week — were 60% less likely to have ADHD symptoms than kids whose mothers ate less. While that seems contradictory, Korrick points out that not all fish is high in mercury, and that eating more fish could have other benefits for brain and behavior development that are worth considering. The current study did not determine what kinds of fish women in the study ate, however.

(MORE: New Dietary Guidelines: Cut Salt and Sugar, Eat More Fish)

This balance between the benefits and harms of fish consumption may also help explain the contradictory results of previous mercury studies. In those that show no increased risk of ADHD or other behavioral symptoms, the participants could have been heavy fish consumers overall, so the benefits of their diet for children’s neurocognitive development may have offset the harms from mercury. In contrast, in those studies showing a harmful effect of mercury at low levels, the negative effects of mercury may have overwhelmed any potential benefits of fish, if the participants had consumed primarily fish species that were high in mercury and perhaps low in omega-3s.

The U.S. Environmental Protection Agency urges pregnant women to limit their fish consumption to two 6-oz. servings a week in order to protect developing babies. Large, deep-water species such as tuna, swordfish and mackerel, which are among the more popular options on restaurant menus, also tend to be higher in mercury than smaller, oily fishes, such as salmon, herring and sardines. Learning which fish are nutritious but low in mercury — others include catfish, tilapia and whitefish — takes a bit of work, but organizations such as the Food and Drug Administration and the National Resources Defense Council have useful lists.

“It’s not necessarily contradictory,” says Korrick of the advice to eat fish, yet avoid mercury exposure. “It would be an unfortunate public health message if people stopped eating fish because of the concern over mercury. Understanding and appreciating that mercury avoidance is a prudent thing to do during pregnancy is important, but understanding and appreciating that fish consumption is important is worth remembering as well. Eating fish isn’t equivalent to getting exposed to mercury.”

MORE: Will We Finally Get Mercury Out of Our Food?

12 comments
sdgso1
sdgso1

Mercury is a known toxin.  one of many "heavy metals" that are known toxins to our bodies.  no different than lead, which the government has done cartwheels to "protect" us all from.  But mercury is different because the pharmaceutical companies used it for YEARS (and still do in flu shots) as a preservative.  THAT's why you hear it is not dangerous, but oh, wait, it is!   follow the money.  stay away from anything with mercury - dental fillings, tuna, etc.   you can eat fish, just be careful of the ones known to harbor mercury, such as tuna.  

and no, you cannot trust the government to be totally honest.  you have to do the research, and then make educated decisions for you and your loved ones.

BrookeD1717
BrookeD1717

David Ropeik, an award winning journalist and former Harvard instructor, responds to the media coverage of this latest mercury and fish report in, “How The Media Put Us At Risk With The Way They Report About Risk.”. 

He says, “… the coverage of this new mercury study demonstrates something more worrisome about how the media cover risk in general, something that is directly harmful to your health and mine. It’s not just the alarmist way they report things, but also a matter of which stories and facts they report, and which ones they simply don’t.”. 

You can find his great article here: http://bigthink.com/risk-reaso....

Michelle Love
Michelle Love

First they say the mercury in vaccines is safe- then they take it out. Now they say the mercury is affecting our children"s brains. I wonder where the truth lies?

Michelle Love
Michelle Love

First we were told the mercury in vaccines doesn't cause autism; then they took it out. Now they say the levels in the fish are affecting our kids' brains- I wonder if they are even capable of telling us the whole truth, ever.

wholefed
wholefed

Please be aware that a number of fish oil supplements contain mercury.

Fish do not actually produce omega-3 fatty acids, but instead accumulate them by consuming either algae or other fish that have accumulated them. 

Fish Oils have received an enormous amount of attention in recent years as a cure-all for a number of chronic diseases; including heart disease, cancer, depression all the way to dementia. As with any supplement that is heavily marketed and associated with large corporations the benefits of taking a fish oil supplement have to be examined.

Supplements are not a substitute for good nutrition. In regards to fish oil; a couple of tablespoons of flax-seed, a green leafy salad, and a handful of chia seeds should do the trick. No issues: no PCB’s, no environmental stress on the world’s fisheries, no mercury and no added expense.

A “Good” Cholesterol Fish Story:  http://wholefed.org/2012/05/17...

Ian Welch

fmondana
fmondana

"The finding raises the possibility that the health benefits of eating

fish, which is rich in the omega-3 fatty acids that are good for brain

development, could outweigh the harms of low-level mercury exposure."

What data shows the link between omega-3 and brain development?

How many people would take the time to find this information? Too many of us decide the veracity of articles based on where it was published or who wrote it. Would any of you buy a car only because a favorite celebrity endorsed it? We should be at least as interested in what we accept as fact for our health as what car we drive.

I'm not faulting anyone here but more articles (especially health related) need to be written with links to sources and other references the writer used. Peer reviewed articles must show sources so the reader can study the paper without simply accepting the content as correct. This would be a good practice for these articles as well.

There might be a bit less of the "controversy" around such things as immunizations. Right now those who believe inoculations are harmful learned about it from a few pages written by an actress/model and a "Doctor" who has been discredited. I've spoken to 23 anti-shot folks and none of them have done any real research or even use critical thinking skills. Most of them would stop reading research (usually after less than 3 paragraphs) if it didn't support their own views.

Austin Arnold
Austin Arnold

Also those flu vaccines have mercury in them, just pump your kids full of it and wounder why they act weird.

davee44
davee44

Eat the fish, it may save your health!  The ADHD, obesity and Diabetes is from the governments own processed foods not the fish!  The government has poisoned the people with legal poison called "Processed foods". 

Scientist in Europe showed The food was changed in the USA, UK and Australia 30 years ago when dangerous food chemicals from the USA was allowed into Europe. The food today causes stubborn insulin If you have stubborn insulin you hold fat and have a hard time losing weight. You can eat very little and the weight still does not come off. Stubborn insulin will hold fat and diets won’t work. When researchers used a specialized diabetes diet on overweight people all lost weight even those who did not have diabetes.just google SPIRIT HAPPY CURE

Jose Estrella Hazim
Jose Estrella Hazim

I am finding ways to tell you, man: If you talk to people with this disorder, for example, by whispering scientific nature/things to their ears, isn't that equal to, for example and not in an abusive way/form other, telling scrambled words to them so they can hear anything and when them get confused, telling them that bad things only will occurs, so your spelling can go, I don't know, went or the like, THROUGH? Listen that, poetry, because that is the only effect garbage or a s.it/thing can obtain or get from, if any, or of course, some, why not, too. By@Hey.U

Commentonitall
Commentonitall

NEWS ALERT

Parents not parenting and afraid to tell their kids no leads to ADHD.  Also, the false assumption that society and public schools should raise your kids leads to ADHD as well.  Lastly, America seems to be the only society with ADHD afflictions leading researches to conclude there is no such thing and our culture and lack of action leads to little brats.

Michelle Love
Michelle Love

 Hey, I have an idea! Read a book! they are fascinating, really,and you LEARN things! America just happens to be one of the most toxic environments in the world and ADHD is a real and painful problem for many. Your ignorance is staggering.

Commentonitall
Commentonitall

That's funny, reading and observation of American society first hand is exactly what led me to my conclusion. I agree with America being toxic and the points I made in my initial comment are the reasons for that toxicity. The only reason "ADHD" is a problem for our kids is the lack of parenting and allowing the social media and television to be the way most young children interact with the world at a young age. The only painful part of ADHD is the parents of these kids and watching them fold to every whim of their children. You don't have discussions with children and ask them to do things, you command them while loving them and they obey. That is the way I was raised and I have a great attention span, good education which I paid for by myself a decent job and meaningful relationships without any of these "ailments" which require medication. The pharmaceutical companies are stealing your money by making up propaganda to perpetuate their sales and you are one of the many that fall for it, I feel sorry for you. People need to suck it up, grow a set and be adults about their situations instead of pointing the finger at a fictitious ailments because they fail to accept personal responsibility, that is the true toxin in American society, pointing the finger at anyone but yourself.

Subject: [healthland] Re: Mom’s Exposure to Mercury Linked to Kids’ ADHD Symptoms