MERCURY::Yes, it causes cognitive problems, but then again. . .

Medical research papers can be long and tedious, so it’s no wonder that most readers turn to the short summary and conclusion. And, if you’re really rushed, you just read the conclusion. The trouble is, the conclusion is often the part of the study that is most open to interpretation.
Take, for instance, a study that’s just come out about mercury in fish. Mercury is one of the deadliest poisons known to man, which is why, of course, we put it into our teeth as dental fillings. But more recently we’re also being exposed to dangerous levels of mercury from the fish we eat as well as from industrial waste disposal.
Everyone seems to agree that fish deliver the highest level of mercury (and if we didn’t, thousands of dentists might face law suits), and it’s something that has even begun to worry health groups, who have been urging people to cut down on the amount of fish in their diets.
As mercury distributes rapidly through the body, and it easily crosses the blood-brain barrier, the $64 billion billion question is: does it affect our cognitive faculties. In other words, can it lead to dementia and even Alzheimer’s?
The whole world, and its lawyers, would like the definitive answer to this one. So it was a brave bunch of researchers from the Johns Hopkins Bloomberg School of Public Health that decided to find out. They used as their subjects 474 participants in the Baltimore Memory Study, and assessed their mental capacities and the levels of mercury in their blood.
The researchers discovered that participants with higher levels of mercury in their blood fared badly in a test of visual memory.
So that’s that then. Well, no, you see the conclusion says that ‘the data do not provide strong evidence that blood mercury levels are associated with worse neurobehavioral performance in this population of older urban adults’.
A strange conclusion? Well, the researchers also tested the participants for their manual dexterity, and this seemed unaffected. So were they right to conclude that there was ‘no strong evidence’ when it was clear the mercury levels were affecting their visual memory? Interpretation, interpretation.