No, fish is actually very good for you and that’s why it’s recommended that we eat at least two portions a week, one of which should be oily. However, eating oily fish in excess may be harmful because of the pollutants they contain, such as dioxins and polychlorinated biphenyls (PCBs). These have no immediate effect on health, but can be harmful if they build up in our bodies over time, so there are now upper limits on how much people should eat. Adult men should not have more than four portions per week, and no-one should eat shark, swordfish or marlin more than once a week because these fish are the most likely to be contaminated with mercury. There is no limit on how much white fish you can eat.