There was a big flap about this a few years ago. The show "60 minutes" came out with a big expose on this this, but to their credit, they also brought on some of the "Experts", and the conclusion was, yes, there is a risk of sorts, but they can't really quantify it. The kid in the story was eating probably -3 tins a day (6 1/2 oz, per tin, don't know exactly what that translates to grams, probably close to 350-400 gr). Pretty much what Ironman said. Seems that the recommendation the "guru" on the show said, 5-6 tins / week sholuld be fine. I have NOT heard the same when it comes to the cold water fish; i.e. the common ones found in tins being herring, mackerel, sardines and salmon, which are all MUCH higher in the omega 3 fatty acids. I get my hring salt cured, and get the mackerel-jack in tins at a cheaper tprice than tuna. Daniel, I think you're from the UK, and when I was shipping out of Glasgow, Scotland, UK, we used to go down to the local fish mongers and get lightly pepper smoked Mackerel at a very inexpensive price.