Prenatal Mercury Exposure and Fish Intake Linked to ADHD

A new study suggests that exposure to mercury during pregnancy may increase the risk for attention deficit hyperactivity disorder (ADHD), while eating fish may reduce this risk.

Mercury is a neurotoxin, meaning it affects the nervous system. For fetuses, infants and children, the primary health effects of mercury are on nerve development. Even low levels of mercury exposure, such as may be the result of a mother's consumption of methylmercury in dietary sources (such as fish), may negatively affect the brain and nervous system. Impacts on memory, attention, language and other skills have been found in children exposed to moderate levels in the womb.

Oils from salmon, trout, tuna, herring, sardine, mackerel, eggs and some chicken contain omega-3 fatty acids that are needed to build brain tissue. Intake of omega-3 fatty acids during pregnancy may provide nutrition for proper brain and retina development of the fetus. However, fish absorb methylmercury from water as it passes over their gills and as they feed on aquatic organisms. Larger predator fish, such as swordfish and tuna, are exposed to higher levels of methylmercury from their prey.

In a new study, researchers assessed the potential relationships between prenatal mercury exposure and fish consumption with ADHD in children using hair mercury measures from 421 mothers and reports of fish consumption during pregnancy from 515 mothers. A teacher rating scale and other testing methods were used to identify ADHD-related behaviors in eight year-old children.

The researchers found that mercury exposure was linked to inattentive and hyperactive behaviors in children. Maternal hair mercury levels of one microgram per gram or greater were associated with a 40 percent increased risk of inattentive behavior in children and a 70 percent increased risk of hyperactive behavior. Conversely, regular fish consumption was linked to a decreased risk for ADHD-related behavior.

The authors noted that these findings highlight the need to balance the potential benefits and risks of eating fish during pregnancy. Further research is warranted.

For more information about pregnancy or ADHD risk factors, please visit Natural Standard's Medical Conditions Database.

Comments

[SB]

I find it interesting that this surprises so many people. I live in Canada, and during our prenatal care we are told over and over again to avoid fish during pregnancy for this reason.

[AR]

It is unfortunate that something as healthy as fish can be just as detrimental to a fetus due to the mercury content. Omega-3 fatty acids found in fish can aid in brain development, but mercury, which can be found in high levels in tuna and swordfish, may damage the brain or increase the risk of ADHD in a fetus. This study found that fish consumption in children may decrease ADHD symptoms, but fish consumption by the mother before the child’s birth may increase the risk of ADHD symptoms. You might be able to buy fish that “guarantees” low mercury levels, but how can a consumer prove if these claims are true. As an expecting mother would you really want to take the chance? Until more research is done perhaps mothers should stick to consuming non-fish sources of omega-3, such as flaxseed.

[SS]

This is an interesting article. Pregnant women are supposed to stay away from fish because of the mercury but yet the same fish could help with ridding the body of the mercury. It seems kind of confusing. I think the best recommendation would be to stay away from fish in general and give an omega-3 supplement.

[AM]

I find it interesting that so many sources are touting fish as a great substitute for red meats, when there is this issue that has been around for so long. Eating fish that are high on the food chain like tuna results in high levels of mercury ingestion. I think this is a good guide put out by the FDA detailing how much fish is acceptable in pregnancy.

http://www.fda.gov/food/foodsafety/product-specificinformation/seafood/foodbornepathogenscontaminants/methylmercury/ucm115662.htm

[ac]

This is a very interesting discovery. Pregnant women are often warned to be aware of how much and what kind of fish they are eating during pregnancy. This may well be another important reason to be careful. Hopefully further research will be conducted, so mothers to be can make an informed decision about eating fish.

[JH]

Some mercury occurs naturally in the environment and almost all fish have some amount of mercury in them. The high levels of mercury are related to industrial pollution, which builds up in the ocean. Larger fish that live longer accumulate higher mercury levels over time than small, younger fish.

[J Squared]

It is essential that studies pertaining to women’s health, particularly in pregnant females, are continuing to be investigated. There is still a lot to be discovered about what may be of benefit to use or not to use while being pregnant or breastfeeding. It seems that the consumption of fish based on this study would be left at the discretion of the pregnant women and for them to judge whether the risks outweigh the benefits and vice versa. It would be interesting to see to a comparative study of whether supplemental omega-3 would be just as effective at reducing ADHD as regular fish consumption, but without the hassle of mercury ingestion.

[ML]

It is scary that even low levels of mercury can affect the nerves. It is easy to receive the omega 3 fatty acid through supplements. I wonder if many pregnant women have been eating fish during their pregnancy because of the recent surge of kids with ADHD. But then there is always the debate about ADHD or just a kid being a kid.

[ks]

This is an interesting article. I've read that mercury consumption in pregnant women can damage the baby's brain and nervous system development. It's a bit nerve racking to know that eating certain fish can harm your baby's development, while other type of fish/fish oil can promote brain development. I think if I was a pregnant woman, I would just avoid this category of food in general to be safe.

[JH]

It is very important that pharmacists educate their patients about mercury in fish oil supplements and how they can avoid or reduce their chances of exposure by purchasing their supplements from reputable manufactures with quality control. Generally speaking, fish oil supplements that they are derived from fish in cold water have less mercury than warm water!

[KJ]

I think as a pharmacist, it is difficult to give medication advise to a pregnant or nursing mother just because so many drugs cross the placenta and can harm the fetus. However, seeing the potential benefits of fish oils on the mother and developing child I would be inclined to recommend them. There are several brands of prenatal vitamins that contain omega-3's. This could be a safe and easy way to obtain the supplement without posing the risk of mercury exposure.

[ss]

So much controversy surrounds potential causes of ADHD and Autism in children. It is most important that pregnant women receive proper, updated nutritional counseling and information about avoiding mercury exposure and also how to safely include fish (Omega 3 Fatty Acids) for optimal development of the fetus. This study is a step in the right direction toward identifying the benefits of eating fish in reducing the risk of having a child with ADHD, where others have discouraged women to avoid fish, but more work must be done. It is not surprising that links between mercury and other industrial waste in the environment can be hazardous, but it is also confusing and upsetting for women to get conflicting advice from different sources about what to eat or what not to eat.

[GP]

I was also wondering if fish oil supplements would have the same risk. Also, not all fish is high in mercury- the highest levels are found in predator fish like grouper, tuna, swordfish, and shark. Plus, surely those omega-3 and omega-6 acids are good for both the baby and mother. Another interesting thing about mercury levels is they depend on whether the fish is wild or farmed. Wild fish tend to have higher mercury levels and higher omega acids, while farmed fish often have lower levels of both. I wonder, then, if the rates of ADHD are higher in countries where seafood consumption is high, like Japan and some Mediterranean countries.

[kt]

While this is an often confusing subject, it is interesting to see that eating fish may not be as terrible for pregnant women as previously believed. Since some types of fish are more prone to accumulating mercury than others, perhaps it is appropriate to eat more salmon than tuna while pregnant. Or simply supplement the diet with omega-3 supplements and avoid fish altogether. This research is particularly important at a time when ADHD diagnosis seems to be on the rise, with more and more kids needing medication to treat their symptoms. Perhaps it is mercury, or a combination of many different environmental factors, but certainly more research is warranted on this rapidly growing disease state.

[nb]

It is a scary thought to think that what a mother chooses to consume during the 10 months of pregnancy could affect the child for the rest of his life. It's interesting to see that while fish provide brain development via supplying omega-3 fatty acids, but also provide concerning levels of neurotoxic mercury. I would be very concerned if I were a pregnant woman and were consuming fish daily. I wonder if omega-3 supplements would have the same bioavailability as the nutrients obtained from fish, without exposure to mercury.