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Mercury, Fish, & ADHD – The Whole Story

Mercury, Fish, & ADHD – The Whole Story

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Anyone paying attention to pediatric medicine over the past decade has noticed the dramatic increase in the incidence of attention and hyperactivity disorders in our children. There are no shortage of theories regarding why this is the case, ranging from environmental exposures to nutritional deficiencies. In all likelihood, the cause will not be pinned down to a single etiology, but is probably multifactoral in nature. However each child’s case a little different. As with many health conditions, some of these causes will be modifiable and within our control, while others will not.

To this regard, there is a fascinating study examining the relationship between a mother’s fish consumption during pregnancy, how that consumption affects prenatal mercury levels, and the related incidence of later development of ADHD-type symptoms in her child. At first take, the results are somewhat confounding. On one hand, elevated fetal exposure to mercury, through increased maternal fish consumption, was linked to increased impulsivity/hyperactivity behaviors later in life. This was shown to be true even with relatively low levels of mercury exposure, far below those regulated by the FDA. However, the study also found that a mother’s intake of two or more servings of fish per week led to a reduced instance of ADHD symptoms in her child.

These two conclusions seem contradictory, but on deeper consideration we can see that the truth is just a bit more complicated. It is certainly true that more and more research is identifying the neuro-protective elements of fish, at least partially due to its high omega-3 fatty acid content. These omega-3 fats provide docosahexaenoic acid (DHA), which is necessary in the healthy growth and function of nervous tissue, including the brain. So we are able to draw the simple conclusion that more fish in pregnancy equals higher levels of omega-3 fats in circulation, which equals better brain development in the child. That is, until you take mercury into account.

As a result of our industrial practices, mercury has contaminated the oceans. The primary sources of mercury into our waterways are coal combustion and the refinement of precious metals, such as gold. It is present in very small quantities in the seawater itself, but as it makes its way up the food chain, from algae to smaller fish to larger fish, the quantity of mercury is exponentially magnified. It is found in the highest amounts in large predatory fish such as shark, swordfish, and tuna. Through mother’s consumption of these fish, this accumulated toxic metal is transferred in measurable quantities to the unborn child, and it’s its presence is highly detrimental to the developing human brain. The cognitive and behavioral assessments of the children in this study were done at eight years old, suggesting the very significant long-term impact of the choices made during pregnancy.

So how do we make sense of this information? Should a pregnant mother eat fish or avoid it? In the end, it comes down to making smart, informed decisions about what fish to eat, and how often to eat it. Generally speaking, smaller fish like sardines and wild salmon are the best, while larger fish like Chilean sea bass and swordfish are to be avoided. Since the most commonly consumed fish in America is canned tuna, it is worthwhile to specifically mention the differences between what is available at the grocery store. Albacore tuna, known for its white flaky consistency, has by far the highest concentration of mercury. It should be totally avoided in pregnancy. A better choice is chunk light tuna (usually a species called skipjack), which has on average less than half of the accumulated mercury. Still, it is best to limit any tuna to once per week. A far better option is canned salmon, which contains more omega-3 fatty acids and less mercury than any of the tuna species.

The Natural Resources Defense Council (NRDC) is an excellent resource for this information. Their website contains an up-to-date list of the mercury levels found in different seafood options. You can even print out their wallet sized information card, and have it with you next time you are at the store shopping for a fish dinner.

Additionally, supplementing during pregnancy with a high quality fish oil that has been thoroughly tested for heavy metals is an excellent way to ensure you are getting optimal levels of the omega-3 oils that your developing child needs. Along with a prenatal multivitamin, think of it as the best insurance policy in town.

If you are pregnant, or thinking of becoming pregnant, feel free to contact us at the clinic for additional support in making the best choices for your baby. Remember that seemingly small daily decisions made during those critical months can impact your child’s life forever.

Dr. Craig Fasullo is a licensed naturopathic physician with a family practice in Manchester, CT. All of the physicians at Connecticut Natural Health Specialists are in network with most insurance companies. For more information or to make an appointment, please call (860) 533-0179.