Sources of omega-3
Farm trout "beats" wild trout?
Recently, prices for salmon fish, especially for valuable varieties such as salmon and trout, are not encouraging. But having decided to treat yourself to a delicacy, you also need to solve the question: which fish to prefer – wild or grown in aquaculture? If we take into account not only the taste, but also the health benefits, primarily the content of essential fatty acids known as omega-3? The answer was given by scientists from Krasnoyarsk and Moscow who studied the fatty acid composition of different breeds of rainbow trout grown on a farm and on "free bread".
Article by Gladyshev et al. Differences in composition and fatty acid contents of different rainbow trout (Oncorhynchus mykiss) strains in similar and contrasting rearing conditions is published in the journal Aquaculture.
Rainbow trout is perhaps the most popular fish from the vast salmon family. It is this relatively small (up to 2 kg) salmon that can most often be found on the shelves of shops and on the menus of restaurants around the world. This fish owes its fame not only to the excellent taste of its meat, but also to its accessibility: rainbow trout is not only an important object of fishing, but is also artificially bred everywhere in reservoirs.
Like other fatty fish varieties, such as mackerel and the more democratic herring, rainbow trout serves as a source of valuable long-chain fatty acids having several "unsaturated" double bonds (C = C). These physiologically active compounds are part of the cell membranes, where most of the processes of transformation of matter and energy take place, therefore they are absolutely necessary for the normal functioning of the brain, nervous and cardiovascular systems and the maintenance of metabolism in general.
In fatty acid molecules, carbon atoms can be connected to each other by a single chemical bond, or by a more reactive double (unsaturated) one. Molecules with multiple double bonds are called polyunsaturated (PUFA), and depending on the number of carbon units – short-chain (19 C atoms) or long-chain (20-22 atoms).
All long-chain PUFAs of the omega-3 family are an integral part of a healthy diet. These acids are found practically only in animal fats, primarily fish, marine mollusks and microalgae. And although there is no official dosage of omega-3, most experts recommend that an adult consume at least 250-500 mg per day to maintain health.
For example, the mechanism of beneficial effect on the circulatory system of eicosapentaenoic acid is to increase the synthesis of endohormones that affect blood vessels, as well as the processes of thrombosis and inflammation. A deficiency in the diet of children of docosahexaenoic acid, which provides effective signaling in nerve cells, reduces their ability to learn and inhibits the development of psychomotor functions, and for adults is fraught with an increased risk of depression, schizophrenia and other neurological disorders, including Alzheimer's disease.
Unfortunately, although humans and other animals are able in principle to produce these long-chain fatty acids from the essential short-chain ones (which we get from food, including vegetable), the effectiveness of such synthesis is low. There is only one way out – they must be consumed already in a "ready-made" form, and in reality about 97% of these nutrients a person receives from fish and other aquatic organisms.
And there is an important nuance here. According to the UN, the average annual consumption of fish and seafood per capita is on average 16 kg, which in terms of essential omega-3 acids gives no more than 100 mg. At the same time, the dose recommended for the prevention of cardiovascular diseases is almost an order of magnitude higher.
For humans, the main source of irreplaceable long-chain PUFA is fish. To get a daily dose of these fatty acids, recommended by WHO as a prevention of cardiovascular diseases, it is enough to eat tens to hundreds of grams of this product. For comparison: the corresponding portion of fried pork is over 3 kg! By: (Gladyshev et al., 2006; 2007; 2009).
Therefore, now the quality of fish products in the form of the content of long-chain omega-3 PUFA in it is of crucial importance, which, depending on the type of fish and habitat conditions, can vary by more than 40 times! As for salmon fish, this indicator may decrease markedly with artificial breeding. After all, the same trout is a predator, and it needs food rich in irreplaceable PUFAs, which are produced from invertebrates and fish extracted from natural ecosystems. As a result, more fish biomass is used in salmon farming in Norway than is produced. Therefore, part of the scarce fish oil in the feed is often replaced by vegetable fats. The result is predictable…
One of the ways to increase the nutritional value of fish in aquaculture conditions is the selection and cultivation of breeds capable of synthesizing polyunsaturated fatty acids despite the presence of vegetable oils in the feed.
A team of scientists from Krasnoyarsk and Moscow studied the composition and content of fatty acids in rainbow trout fillets of seven genetic lines grown in the same farm and selected at the same time. Then these results were compared with similar ones for trout from another fish farm, as well as mongrel and wild representatives of the same species from the western part of the Kamchatka peninsula.
The analysis showed that the composition of fatty acids of fish meat in aquaculture as a whole really reflects the composition of their diet. Thus, the Adler and Adler amber lines, grown on feed with vegetable oil, had lower levels of eicosapentaenoic and docosahexaenoic fatty acids. But it turned out that the genetic characteristics of individuals also play an equally important role: the "steelhead" rainbow trout managed to maintain a high level of these nutrients even with a significant content of vegetable oils in the diet.
Unexpected was the fact that, contrary to popular belief, the studied wild fish had significantly lower levels of eicosapentaenoic and docosahexaenoic acids compared to "farm". In addition, along the way, the researchers identified a marker that makes it possible to distinguish "natural" rainbow trout from artificially grown: the meat of the latter turned out to contain less monounsaturated oleic fatty acid, which may be due to low motor activity.
The results of this work indicate the possibility of targeted breeding of rainbow trout to obtain products of high nutritional value regardless of growing conditions, but for now, researchers advise growing the most profitable "steelhead" line on farms. From the point of view of consumers, all this is an undoubted plus, since it gives a chance to buy not only delicious, but also the most healthy fish in the store, and besides, it is possible, at a lower price. And then the problem of choice will disappear by itself…
Publication based on the material of the press release of the FIT Krasnoyarsk Scientific Center SB RAS and the article by Dr. M.I. Gladyshev "Fats - for the mind and heart"
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