 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 of omega-3 fatty acid, is good for brain development, but of course the 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, it found that the adverse effect of mercury on the IQ scores of children exceeded the beneficial effects of the DHA. So much lost brain power from fish consumption that our country may actually lose $5 billion in economic productivity every year. For example, our most popular fish, tuna. 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 eight IQ points. In fact, the only two more brain-damaging fish were pike and swordfish. On the other end of the spectrum, the brain-boosting effect of DHA may trump the brain-damaging effects of mercury and salmon by a little less than one IQ point. Unfortunately, IQ just takes into effect 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, 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?