No, Mercury isn't just that silver stuff in old-timey thermometers. Mercury is a naturally occuring element in the environment and can sometimes be found in your food — most notoriously in fish. Mercury is found in just about all seafood.

While this isn't usually a big deal, Signs of too much mercury consumption include psychological issues, muscle weakness or numbness, difficulty with the senses, and balance issues. As such, some government agencies recommend eating no more than five ounces per week of seafood that's considered high in mercury. If you eat seafood on a regular basis, what fish should you look out for? These are the popular fish with the lowest and highest mercury levels.

Lowest: Anchovies Out of all the fish you could eat, show some of the lowest levels of mercury. This is in part because lower mercury levels are found in smaller fish or that don't eat a lot of other fish (compared to a lot of fish on this list, anchovies are pretty far down on the food chain). Really, the only thing that you need to watch out for with anchovies is the sodium content.

Sometimes, when you get anchovies that come in a can, they can be on the high side; such is the case with options like King Oscar's anchovy fillets in olive oil, which, per serving, come with nearly 40% of your daily recommended sodium intake. Lowest: Atlantic mackerel When you pick up a can of mackerel, chances are that it's Atlantic mackerel, even though there are various different types of mackerel swimming.