A while back, I switched to the Paleo diet and, being stuck for easy-to-prepare food, started having a piece of smoked mackerel for breakfast and for supper every day. I did that for a couple of months and then it occurred to me that maybe that wasn't the idea. Googling around, there seems to be a lot of focus on minimum amounts - that is, you should have at least one piece per week - but things get a bit woolly when it comes to maximum amounts and yet there is a sense that a maximum limit exists. For example: http://www.ifbb.org.uk/how-much-oily-fish-should-i-eat- Suggests a minimum of one and a maximum of four. Is there any rational basis to this? I know there are mercury issues with some fish, but not, apparently, mackerel. And oily fish have lots of omega 3 fats, which are good for the immune system. There's no limit on the amount of meat or white fish you can eat: why a limit on (mercury-free) oily fish?