# Salmonids as Natural Functional Food Rich in Omega-3 PUFA
## 4 Discussion  
Among PUFAs, the omega-3 family dominated in all analyzed fish, while omega-6 levels were significantly lower. This has been noted by other authors too [13; 14; 21]. The omega-3 LC PUFA content in salmon was found to be 1.2 to 1.9 g/100 g of fillets. In other studies, it was from 1.0 to 2.6 g/100 g [14; 21]. In the case of rainbow trout, the omega-3 VLC PUFA content in meat was from 0.9 to 1.2 g/100 g and was similar to that reported in other studies (0.6-1.4 g/100 g) [14]. The differences in omega-3 content depend on many factors, especially the fish's diet. However, it is also associated with gene expression of key metabolic processes, as it was shown in the case of salmon [22]. Fish are a uniquely rich source of omega-3 VLC PUFA in the human diet. Other natural sources of omega-3 VLC PUFA are cultivated marine algae and single cell oils (s.c.o.) obtained from this source, marine mammals and crustaceans as krill. Omega-3 VLC PUFA are also provided by supplements and enriched foods. These can contain fish oil, s.c.o. or krill oil. The ratios of particular omega-3 VLC PUFAs (EPA, DHA and DPA) differ between the various sources, although DPA is usually in a lower level than EPA and DHA [23]. Nevertheless, in recent years, the importance of DPA in health promotion had increased [9]. The European Food Safety Authority (EFSA) dietary recommendations (DRI) indicate that healthy individuals should consume an amount of omega-3 VLC PUFAs between 250 and 500 mg per day. This has been based on cardiovascular risk considerations for adults [23], whereas for patients with documented CHD, 1 g of omega-3 VLC PUFA per day is recommended [3]. One portion of fish meal is 130 g, as advised by the EFSA [24]. Such a portion of farm-raised Norway salmon might provide 2.5 g omega-3 VLC PUFA. However, in a study focused on Scottish salmon, this dose was shown to be 1.8 g [21]. In the case of trout, depending on the species, it was found to be from 1.2 to 2.1 g. Other authors have reported this level to be from 1.5 to 2.7 g. The differences were dependent on fat content in fish as well as fish oil content in the fish's feed, as reported by other authors [25; 26; 27]. Moreover, the ratio of omega-6 to omega-3 PUFAs was much more nutritionally desirable in wild fish than in farm-raised ones. This has been also shown in other studies [27]. Due to the omega-3 VLC PUFA content, it is recommended that everyone should eat two portions of fish per week [10; 28]--especially since most of the Western adult population is at risk of CHD [10]. According to the obtained results, it could be estimated that by following above dietary recommendation by eating two portions of Norwegian salmon per week, 5 g of omega-3 VLC PUFA could be provided, which corresponds to 714 mg per day. This would more than satisfy the daily DRI levels for healthy people and would reach close to the levels recommended for CHD patients. In the case of farm-raised trout, this figure is approximately 3.8 g per week, i.e., 542 mg per day, and slightly less in the case of wild ones. The strong move towards a healthy diet promotes the consumption of fish. Nevertheless, due to overfishing, fish stocks are declining, which also refers to wild salmon and wild trout [2; 5]. Thus, to protect endangered fish species, it is necessary to eat fish from sustainable sources such as aquaculture [29]. Aquaculture production of fish might counterbalance this supply issue. In farm-raised fish, the quality of meat, fatty acid profile as well as the concentration of vitamins and minerals are influenced by fish diet composition [18]. Nowadays, fish feeds contain additions of fish oils, single cell oils and other sources of omega-3 VLC PUFAs. This contributes to increase the omega-3 VLC PUFA level in farm-raised fish [25; 30; 31]. Moreover, other sustainable sources of omega-3 VLC PUFAs for farm-raised fish feeding are considered. One of the new sources of fish feed could be cultured gammarids (_Amphipoda_, _Crustacea_).