Mercury levels in fish is a problem. That swordfish you see? It’s practically dripping with mercury – just like king mackerel, and other large predatory fish. So here’s what you should reel in: according to a Scandinavian study, small, oily fish like sardines, herrings and anchovies contain high levels of heart-healthy omega-3s; and because they’re low on the food chain, they house less mercury than their big brothers. Try canned versions of the little guys mashed into a mustardy dressing for spinach, or on top of an open-faced sandwich of wholewheat bread, cream cheese, thinly sliced red onion and a squeeze of lemon juice.