The nutritional quality of tuna depends on a variety of factors, such as the type of tuna you buy, the differences in the fishery where it was produced/captured, the diet of the fish, and even water temperatures.
Types of Tuna
There are dozens of different tuna fish species, but tuna companies group tuna into three categories:
1. White or albacore
Mild flavor, slightly more expensive that light tunas, and contains higher levels of omega 3 fatty acids compared to light tuna. On the negative side, white tuna is at risk for higher levels of mercury. This is why it's recommend women who are pregnant or nursing and young children should limit their intake of white tuna. White tuna is the only form of tuna that is able to use "white meat" on its label.
Mostly yellowfin tuna and contains a lower level of omega 3 fatty acids compared to white tuna and lower mercury levels.
White and light tuna are most often sold canned, while bluefin tuna is typically sold as a steak. Bluefin tuna is higher in fat that white and light tuna varieties. Bluefin tuna is also at risk for the highest concentrations of mercury.
How the tuna is processed and canned impacts the nutritional value of the meat. If you select tuna canned in oil it will be higher in calories and fat versus tuna canned in water. Also, when you drain the oil from a can of oil-packed tuna you are also draining away some of the omega 3 fatty acids. This fatty acid loss does not occur with water-packed tuna.
Is Tuna a Heart Healthy Food?
Tuna is a fatty fish providing high quality protein, B-vitamins, and selenium. The nutrients help the body produce red blood cells, reduce heart disease risk and macular degeneration, and promote brain growth. The protein provides essential amino acids used for body growth and maintenance, while the fat provides a rich source of heart healthy omega 3 fatty acids.
Many organizations, such as the USDA, American Heart Association, and American Dietetic Association have been encouraging people to eat more fish. This includes eating more tuna. Omega 3 fatty acids have been shown to reduce heart disease risk, blood clots, and stroke, relieve depression, and help fight certain cancers.
How Much Tuna
It's recommended by the American Heart Association that anyone over the age of 2 years-old consume at least 2 servings of fish weekly. A serving of tuna equals 3 ounces for adults.
While I mentioned the risk of high mercury levels about I want to re-emphasize this risk. Eating a diet high in mercury can cause mercury to accumulate in the blood stream. The mercury is removed by the body naturally, but it can be a slow process. High mercury levels can harm unborn babies and compromise the development of young children. This is why the Food and Drug Administration (FDA) recommends pregnancy women, nursing women, women planning to become pregnant, and young children limit the amount of fish they eat, even fish varieties that contain low levels of mercury.
The Environmental Protection Agency provides specific guidelines:
If you weigh less than 110 pounds limit light tuna to one 6 ounce can per week. If you weigh more than 110 pounds you may safely consume 2-6 ounce cans per week.
The Take Away
Tuna is a great addition to a heart healthy diet, providing high levels of heart healthy omega 3 fatty acids. However, how you prepare the tuna will impact the nutritional quality. If you mix the tuna with high fat mayo to prepare tuna salad, you are "cancelling out" some of the benefits.