Tuna is a healthy fish to eat, to a certain degree. As a fatty, cold-water fish, it is rich in omega-3 fatty acids. These are fats that help regulate cholesterol levels and protect against cardiovascular disease.
Tuna also contains an uncommon form of selenium, an essential mineral. However, there is some concern that tuna contains mercury. As a large fish and a top predator, tuna eat fish that may be contaminated with mercury. These fish in turn may have also eaten fish contaminated with mercury. For this reason, some nutritionists advise pregnant women and children against eating too much tuna.