Mercury From Fish Can Affect Cognitive Function in Middle Aged Adults

In reviewing the latest information about mercury and cognition, I became aware of an article that appeared in the Integrative Medicine Journal a year ago.

To study looked at 384 men and women who were mostly corporate executives and who attended an all day company annual physical examination.

They measured the blood mercury levels in all the patients and then looked at the relationship between mercury and cognitive performance in the patients.

The finding was that participants with Mercury levels above 15 mcg/L,showed a 4 to 5% lower complex information processing (CIP)capability, which is commonly called executive function, when they did neurocognitive testing.


The interesting thing from the study was that in those patients with moderate fish consumption, 1 to 3 servings of fish per week, there was no measurable effect on their cognition. This was thought to be caused by the fact that the fish contain essential fatty acids which can improve cognitive function. Therefore the deleterious effects of the mercury were compensated for by the fatty acids in the fish.

The authors rightfully point out that “If cognitive neurotoxicity occurs in healthy, highly productive individuals with ample cognitive reserves, the effect is likely to be amplified in more vulnerable populations.”

They point out that cognitive decline and dementia are an increasing problem as our population is aging. Therefore as seafood consumption also rises in individuals who desire to eat a “heart healthy” diet, this relationship with increased mercury could have a large impact on quality of life, and healthcare costs into the distant future.

This is one of the first studies I’ve seen that actually looks at the effect of mercury on cognitive impairment in middle-aged people. The drawbacks of the study are that that they only looked at one blood specimen and compared it with the patient’s stated history of fish consumption. There is no measurement of mercury exposure over time in the patients.

An even bigger question is what were these patients “Total Body Load” of Mercury? This can only be determined by doing a challenged urine test, with a chelating agent.

What the authors do not point out is that after a person eats fish, the mercury is not eliminated from the body but rather goes into the organs, muscles and tissues of the body where it is stored for the rest of the person’s life! This burden of mercury produces a chronic stress on the neurological, immune, and endocrine system.

In my opinion, this total body burden plays a role in a wide range of diseases from multiple sclerosis to cancer.

The other thing the authors do not point out is that the amount of essential fatty acids contained in each fish serving could be replaced by one Eseential Fatty Acid capsule from the health food store.

My general recommendation to my patient population is still to avoid or minimize fish consumption and take one essential fatty acid pill per day.

Certainly women of childbearing age and women who are pregnant should avoid fish altogether in my opinion. Of course they must take one pill a day of DHA, an essential fatty acid, for their fetuses brain function, along with their traditional Prenatal Vitamin.

I predict that as the oceans increasingly concentrate more and more mercury, and the fish get higher and higher levels of mercury in them, that we will see much more about this in the years ahead.

Read the original article here

Read the whole article here

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Long term neurocognitive impact of low dose prenatal methylmercury exposure

Fish consumption, methylmercury and child neurodevelopment

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Fish Consumption Associated with Brain Shrinkage in Newborns

Physicians have known for many years that mercury in the human body is associated with neurological damage. Fish consumption is the main source of mercury in the human body.

Now a new video from my colleague Michael Greger, M.D.(see below) brings together several journal articles which specifically show how methylmercury in fish is damaging the human brain.

We have known for some time that there is a dose‚ a response relationship of prenatal mercury exposure and IQ. Dr. Greger’s video pointed out to me an article that appeared in the medical literature several years ago on the relation of mercury and newborn’s brains. This article specifically shows that there is a direct relationship between prenatal exposure to a low level of mercury in the mother, and the size of a newborn’s cerebellum.

Specifically in this article it was shown that “prenatal exposure to, what we consider to be, low levels of methylmercury does influence fetal brain development detected as decreased size of the newborn cerebellum.” The decreased size of the newborn cerebellum was up to 14% smaller in length.

What is the cerebellum and what does it do? First of all the cerebellum which is known as the “little brain” is the second largest part of the brain and is located near the base of the brain. Although the cerebellum accounts for only about 10% of the brain’s volume, it contains over 50% of the total number of neurons in the brain.


What is so important about this ? Traditionally the cerebellum has been considered a purely motor control device. However this is now appearing to not be true. Specifically as recently reported in Brain:The Journal of Neurology, researchers have found connections between the cerebellum and the hypothalamus in the brain. These pathways connect with neural circuits that govern intellect, emotion and autonomic function as well as sensorimotor control.

There is a condition called Cerebellar Cognitive and Affective Syndrome (CCAS). This condition occurs in adults and children with stroke or tumor involving the cerebellum. It is also seen in children born very preterm who have a small cerebellum.

The neurobehavioral deficits that occur in this condition can occur in the absence of a motor condition. They are characterized by “impairments in executive function, which includes planning, set shifting, verbal fluency, abstract reasoning, and working memory.” In addition, “impairment in spatial cognition and linguistic processing as well as a dysregulation of their affect” is seen in patients with this condition.

These latter symptoms sound very much like the symptoms that children with Autism Spectrum Disorder, and Attention Deficit Disorder (ADHD)have. We now have an epidemic in our country of neurodevelopmental disorders with an estimated one in five children growing up to have such a disorder. Could mercury be part of the cause?

Watch the video now!

So, given this new information on mercury and the fetus, my first question is how much fish, which is loaded with mercury, is good for a woman while she’s pregnant? The second question is how much mercury has been accumulated by the woman before she conceives which then comes out during pregnancy and affects the fetus and its brain?

The other interesting aspect of this research was the amount of mercury the researchers considered “high” in the mother. The so-called “high levels”, were approximately 1/3 of the level of mercury a woman would get if she ate one can of tuna per week. I find young women in my practice eating tuna sushi several times per week.

In the studies I quoted above, researchers used hair mercury, which is one indication of the body load of mercury. However we now know that not all women excrete mercury into their hair even if they have it in their body.

We realize that the best test for body burden of mercury, is a challenged urine, where a woman takes a medication that is known to be able to pull mercury out of her tissues and put it in the urine where it can be measured.

This is the exact protocol that environmental doctors have been using for so many years. And this in part is why I encourage women in my Preconception Pregnancy Planning Program to get as much mercury as possible out of their body before they conceive.

I encourage you to share this information with your friends and family who are of childbearing age. Encourage them to get off fish before and during pregnancy, and encourage them to find a doctor who can measure their body load of mercury and help clean it out, before they conceive. Nobody wants a child with a small cerebellum, now that we are realizing the importance of this major part of our brain.

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