Tuna fish is generally considered to be a healthy food rich in omega-3 fatty acids. While tuna does contain these essential fats, the truth is that it is also full of dangerous contaminants due to pollution from industrialization. Mercury in particular is found at varying levels in just about all seafood. Because mercury accumulates in the tissues of fish over time, the larger, predatory fish are the ones that contain the greatest levels of this toxin. Tuna, along with shark, king mackerel, tilefish, and swordfish are some of the fish highest in mercury. Pregnant women or women at risk of becoming pregnant are advised to not eat these fish. Mercury in fish crosses the placenta and goes to the brain and nervous system of the developing fetus.

Plenty of research has been conducted on the relationship between omega-3 fats and heart health, brain and eye function, skin conditions, and chronic inflammation. Fish are a great source of omega-3s; however the amounts vary based on the species of fish. Fatty fish such as tuna, mackerel, sardines, and salmon are the best sources. Where do the fish get their omega-3s? They get them from the algae they eat. While humans do not typically eat algae, we do eat leafy greens and these are an excellent source of omega-3s, along with walnuts and flax seeds. While fish can be a part of a nutritious meal plan, don't worry if you don't like to eat them because they are not an essential requirement of a healthy diet. Just be certain to include plant sources of omega-3s in your meals.

Tuna poses the largest health threat to Americans, not because it is the fish highest in mercury, but because of the high level of tuna consumption in comparison to other mercury-laden fish. The Environmental Protection Agency (EPA) has put together a chart to help you determine how much tuna is safe to eat based on your weight. It compares white albacore to chunk light tuna, as white albacore contains higher levels of mercury. For example, if you weigh 120 pounds you should not eat more than one can of white albacore more often than once every 11 days or more than one can of chunk light tuna more often than once every 4 days.

A great information-packed website to check out is the Blue Ocean Institute (blueocean.org) where you can look up the sustainability of just about any type of seafood. If you type in "tuna" you will see that different varieties of tuna receive different sustainability ratings. Albacore tuna gets a green rating, which is the best and indicates that these fish are a good choice as far as maintaining their populations and creating low amounts of bycatch. Atlantic blue fin tuna however, received a red rating which indicates that this fish has been exploited, overfished, and high numbers of sea turtles and sea birds are caught up in bycatch along with the tuna. These sustainability ratings do not indicate the nutritional value of the fish but they do give the consumer one more thing to consider when choosing their seafood.