Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), found in seafood, are essential fatty acids and therefore must be obtained from the diet. Traditionally, Japanese cuisine is centered around fish as the main ingredient. However, in recent years, a social problem has arisen wherein members of both the younger and the older generations eat progressively less fish. Canned fish is an easy-to-prepare fish food, but because vegetable oil is added to the can, it is important to investigate whether canned fish is an appropriate source of n-3 fatty acids. In this study, we divided canned tuna products by fish and oil type and analyzed fatty acid content in the fish part and the oil part to simulate an ordinary serving. From the 300 top-selling tuna can products, we selected 3 different types of tuna (bluefin tuna, yellowfin tuna, and albacore tuna) packed in soybean oil, as well as albacore tuna packed in 4 types of oil (soy, cottonseed, olive, and safflower oils). Furthermore, cans of the 3 types of tuna packed in water were used as controls. The findings revealed that tuna in water contained a suitable amount of n-6/n-3, but a low amount of EPA+DHA. Among tunas in oil, albacore tuna had the higher level of EPA+DHA, and added olive oil contained the lower amount of n-6/n-3. Our finding showed that n-3 fatty acid content in tuna varies widely depending on the added oil, and that the EPA+DHA level of canned tuna is low. Therefore, it is not so appropriate the canned tuna as a source of omega-3 fatty acids.
The consumption of seafood in Japan has continued to decline, and consumption of meat is increasing. One reason for this is that it takes time to cook fish. Therefore, we focused on fish roe that require little cooking time, and examined whether they can be used as a food source of n-3 fatty acids. We selected salmon (sujiko and ikura), herring, cod, flounder, flying fish, and smelt roe, and measured their eicosapentaenoic acid (EPA) content, docosahexaenoic acid (DHA) content and n-6/n-3 ratio by fatty acid analysis. In addition, cooked cod, flounder, and smelt roe were analyzed. The amounts of EPA and DHA in each fish roe were in the order salmon roe 1 (sujiko)> smelt roe ≒ salmon roe 2 (ikura)> cod roe ≒ flounder roe > herring roe > flying fish roe. There was no difference in the amount of EPA, DHA, and fatty acid composition between raw and cooked roe. All fish roe contained only traces of n-6 fatty acid, and the n-6/n-3 ratio was as low as 1 or less. Our results showed that EPA and DHA can be easily acquired from fish roe, particularly salmon roe. Moreover, the EPA and DHA content of fish roe was not decreased by cooking, so they are suitable as a food source of n-3 fatty acids.