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).
Images thanks to tomhe via Flickr.
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 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 groups, 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? Well, look, the DHA in fish, that 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 effects of DHA. So much lost brainpower from fish consumption that our country may actually lose $5 billion in economic productivity every year.
For example, our most popular fish—tuna. If pregnant women ate tuna every day 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 8 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 1 IQ point. Unfortunately, IQ just takes into affect the cognitive damage caused mercury, not the adverse effects on motor function and attention and behavior 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 in intelligence at all when pregnant women can get all the DHA they want from microalgae supplements without any of the contaminants. Get the brain boost without the brain damage.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.
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More on PCBs in:
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 is a rare circumstance where I recommend supplements, but there is at least one (vitamin B12) that is critical for those eating plant-based diets. My latest summary of recommendations can be found here.
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