Mercury vs. Omega-3s for Brain Development

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Risk/benefit analysis of 33 fish species contrasts the brain-boosting effects of DHA with the brain-damaging effects of mercury, to determine the net effect on intelligence (IQ).

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Just because fish-eating mothers may give birth to children with smaller brains, doesn’t necessarily mean their children will grow up with neurological defects. But using real-time functional MRI scans, you can actually see the difference in brain activation in teens whose moms ate a lot of seafood when they were pregnant. This is what a normal brain looks like when you flash a light in someone’s eyes. But, this is what you see in the mercury- and PCB-exposed brains—suggesting “toxicant-related damage” to the visual centers in the brain. Fish consumption may also increase the risk of our children being born with epilepsy.

Does maternal fish consumption have an effect on how smart our kids turn out, though? Well, look; the DHA in fish—the long-chain omega-3 fatty acid—is good for brain development. But, of course, mercury is bad for brain development. So, what these researchers did was look at 33 different fish species to see what the net effect of these compounds would have on children’s IQ. And, for most fish species, they found that the adverse effect of mercury on the IQ scores of children “exceeded the beneficial effect[s] of DHA.” So much lost brainpower from fish consumption that our country may actually lose five billion dollars in economic productivity every year.

For example, our most popular fish—tuna. If pregnant women ate tuna everyday, the DHA in the fish would add a few IQ points. But, the mercury in that very same tuna would cause so much brain damage that the overall effect of eating tuna while pregnant would be negative—wiping out an average of eight IQ points. In fact, the only two more brain-damaging fish were pike and swordfish.

At the other end of the spectrum, the brain-boosting effect of DHA may trump the brain-damaging effects of mercury in salmon, by a little less than one IQ point. Unfortunately, IQ just takes into affect the cognitive damage caused by mercury—not the adverse effects on motor function, and attention, and behavioral deficits. We think that attention span may be particularly vulnerable to developmental mercury exposure—probably due to damage to the frontal lobes of the brain.

And, the IQ study didn’t take into account the relatively high levels of PCBs in salmon, and the accompanying concerns about “cancer risk.” Adding sustainability concerns adds another wrinkle, as farm-raised salmon are considered a “fish to avoid.” Whereas king mackerel is considered a “best” choice for sustainability, the mercury levels are so high as to warrant avoiding consumption—exceeding both the FDA and EPA action levels for mercury contamination. 

The way I look at it is why accept any loss of intelligence at all, when pregnant women can get all the DHA they want from microalgae supplements, without any of the contaminants—getting the brain boost, without the brain damage.

Please consider volunteering to help out on the site.

Images thanks to tomhe via flickr

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Just because fish-eating mothers may give birth to children with smaller brains, doesn’t necessarily mean their children will grow up with neurological defects. But using real-time functional MRI scans, you can actually see the difference in brain activation in teens whose moms ate a lot of seafood when they were pregnant. This is what a normal brain looks like when you flash a light in someone’s eyes. But, this is what you see in the mercury- and PCB-exposed brains—suggesting “toxicant-related damage” to the visual centers in the brain. Fish consumption may also increase the risk of our children being born with epilepsy.

Does maternal fish consumption have an effect on how smart our kids turn out, though? Well, look; the DHA in fish—the long-chain omega-3 fatty acid—is good for brain development. But, of course, mercury is bad for brain development. So, what these researchers did was look at 33 different fish species to see what the net effect of these compounds would have on children’s IQ. And, for most fish species, they found that the adverse effect of mercury on the IQ scores of children “exceeded the beneficial effect[s] of DHA.” So much lost brainpower from fish consumption that our country may actually lose five billion dollars in economic productivity every year.

For example, our most popular fish—tuna. If pregnant women ate tuna everyday, the DHA in the fish would add a few IQ points. But, the mercury in that very same tuna would cause so much brain damage that the overall effect of eating tuna while pregnant would be negative—wiping out an average of eight IQ points. In fact, the only two more brain-damaging fish were pike and swordfish.

At the other end of the spectrum, the brain-boosting effect of DHA may trump the brain-damaging effects of mercury in salmon, by a little less than one IQ point. Unfortunately, IQ just takes into affect the cognitive damage caused by mercury—not the adverse effects on motor function, and attention, and behavioral deficits. We think that attention span may be particularly vulnerable to developmental mercury exposure—probably due to damage to the frontal lobes of the brain.

And, the IQ study didn’t take into account the relatively high levels of PCBs in salmon, and the accompanying concerns about “cancer risk.” Adding sustainability concerns adds another wrinkle, as farm-raised salmon are considered a “fish to avoid.” Whereas king mackerel is considered a “best” choice for sustainability, the mercury levels are so high as to warrant avoiding consumption—exceeding both the FDA and EPA action levels for mercury contamination. 

The way I look at it is why accept any loss of intelligence at all, when pregnant women can get all the DHA they want from microalgae supplements, without any of the contaminants—getting the brain boost, without the brain damage.

Please consider volunteering to help out on the site.

Images thanks to tomhe via flickr

Doctor's Note

What was that about smaller brains? See Fish Intake Associated With Brain Shrinkage. For the effect of fish on teens, see Nerves of Mercury.

For more on PCBs, see:

The “package deal” concept is a recurring one (see, for example, New Mineral Absorption Enhancers Found). Yes, dairy products are the #1 source of calcium in the U.S., but they’re also the #1 source of saturated fat. Thankfully, there’s a way to get calcium without all this baggage, and the same with DHA (and iron, and protein, and…).

It’s a rare circumstance where I recommend supplements, but there is at least one (vitamin B12) that is critical for those eating plant-based diets. For my latest summary of recommendations, see my blog post Optimum Nutrition Recommendations.

For further context, check out my blog post Top 10 Most Popular Videos of 2013.

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