Omega-3-fedtsyre

Omega-3-fedtsyren ALA's kemiske struktur med kulstofatomernes nummerering

Omega-3-fedtsyre (også n-3 og ω-3) er betegnelsen for en familie af flerumættede fedtsyrer som har det til fælles, at de har en dobbeltbinding på kulstofatom nummer tre fra kulbrinteenden, den position på kulbrintekæden som kaldes ω-3 (omega-3).^[1]

Omega-3-fedtsyre kaldes også fiskeolie, men det er lidt misvisende, da fisk (kun) får omega-3-fedtsyre direkte eller indirekte fra alger. Opdrættede fisk har typisk et lavt indhold af omega-3-fedtsyre.^[2]

Ernæring

Nogle af de vigtigste omega-3-fedtsyrer, ernæringsmæssigt set, er alfalinolensyre (ALA), icosapentaensyre (EPA) og docosahexaensyre (DHA).^[1]

Den menneskelige krop kan ikke syntetisere omega-3-fedtsyrer fra bunden, men den kan syntetisere alle de nødvendige omega-3-fedtsyrer ud fra den simple omega-3-fedtsyre alfalinolensyre (ALA), men kroppens evne til at lave denne konvertering, er begrænset.^[1] Derfor er alfalinolensyre (ALA) en essentiel fedtsyre som skal indtages med kosten.^[1] Men grundet kroppens begrænsede evne til at lave de andre omega-3-fedtsyrer (EPA, DHA) fra ALA, kaldes (EPA, DHA) også essentielle fedtsyrer.

Kilder til omega-3-fedtsyrer

Gode kilder til omega-3-fedtsyrer er chiafrø, hørfrøolie, rapsolie, valnøddeolie og valnødder.^[1] Spiseolie baseret på industrihamp har også et højt indhold af omega-3-fedtsyre; omega-3:omega-6 (1:3).^[3]

En anden kilde til omega-3-fedtsyrer er (visse) alger (fx mikroalgen Schizochytrium). Vildtlevende fisk får netop deres omega-3-fedtsyrer fra disse alger - fx de vildtfangede fede fisk, som fx makrel, laks, sild, ansjoser og sardiner.^[1]^[4]^[5] Vildtfangede krill (og dermed krillolie) er også rig på omega-3-fedtsyrer.^[6]

Forskning i akvakultur (og muligvis akvaponi) producerede tilapia har afdækket, at de har lave niveauer af det gavnlige omega-3-fedtsyre (en essentiel ernæring, som er en vigtig grund til at diætister anbefaler fiskespisning) og et relativt høj indhold af omega-6-fedtsyre - omega-3:omega-6 forhold på 1:11, hvilket er meget mindre omega-3 end ønsket.^[7] Rapporten foreslår, at grunden er, at opdrættet tilapia fodres med store mængder majs. Majs indeholder kortkædede omega-6-fedtsyrer, som bidrager til, at de opkoncentreres i fisken.

Kilder/referencer

^ ^a ^b ^c ^d ^e ^f nih.gov: Omega-3 Fatty Acids. Fact Sheet for Health Professionals Citat: "...The two major classes of polyunsaturated fatty acids (PUFAs) are the omega-3 and omega-6 fatty acids...Several different omega-3s exist, but the majority of scientific research focuses on three: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)...The human body can only form carbon–carbon double bonds after the 9th carbon from the methyl end of a fatty acid [1]. Therefore, ALA and linoleic acid are considered essential fatty acids, meaning that they must be obtained from the diet [2]. ALA can be converted into EPA and then to DHA, but the conversion (which occurs primarily in the liver) is very limited, with reported rates of less than 15% [3]. Therefore, consuming EPA and DHA directly from foods and/or dietary supplements is the only practical way to increase levels of these fatty acids in the body...ALA is present in plant oils, such as flaxseed, soybean, and canola oils [3]. DHA and EPA are present in fish, fish oils, and krill oils, but they are originally synthesized by microalgae, not by the fish. When fish consume phytoplankton that consumed microalgae, they accumulate the omega-3s in their tissues [3]... Plant oils that contain ALA include flaxseed (linseed), soybean, and canola oils [2,3]. Chia seeds and walnuts also contain ALA...The omega-3 content of fish varies widely. Cold-water fatty fish, such as salmon, mackerel, tuna, herring, and sardines, contain high amounts of LC omega-3s, whereas fish with a lower fat content—such as bass, tilapia and cod—as well as shellfish contain lower levels [3]. The omega-3 content of fish also depends on the composition of the food that the fish consumes [24]. Farmed fish usually have higher levels of EPA and DHA than wild-caught fish, but it depends on the food they are fed [24,25]. An analysis of the fatty acid composition of farm-raised Atlantic salmon from Scotland showed that the EPA and DHA content significantly decreased between 2006 and 2015 due to the replacement of traditional marine ingredients in fish feed with other ingredients [26]. Beef is very low in omega-3s, but beef from grass-fed cows contains somewhat higher levels of omega-3s, mainly as ALA, than that from grain-fed cows [27]...Table 2: Selected Food Sources of ALA, EPA, and DHA [29]...", backup
^ netdoktor.dk: Fiskeolier (omega-3 fedtsyrer) Citat: "...De egentlige fiskeolier omfatter EPA (eikosa-pentaen-syre) og DHA (dokosa-hexaen-syre). ALA (alfa-linolen-syre) er en omega-3 fedtsyre i planteverdenen, der i mindre grad bliver omdannet til EPA og DHA i vores stofskifte...", backup
^ "Hemp Oil". InnVista. november 2005. Arkiveret fra originalen 17. september 2012. Hentet 18. november 2006. Citat: "...Hemp seeds are the only natural source to boast of having the ideal ratio of EFAs required by the human body, which is roughly 3:1 of omega-6 to omega-3, the two most important EFAs..."
^ 4. mar 2013, ing.dk: Svenskere vil presse sunde olier ud af alger og skåne fiskene. Svensk forsker har sprunget fisken over og er gået direkte til kilden i jagten på de sunde omega-3-fedtsyrer. Citat: "...»Men det er de samme nyttige fedtsyrer, DHA og EPA, der findes i algerne, for det er fra algerne, de fede fisk får sin omega-3,« forklarer forskeren..."
^ Nov 29, 2012, kth.se: Fredrika Gullfot cultivates algae that could replace fish and crude oil Arkiveret 4. juli 2013 hos Wayback Machine Citat: "...“Fish oil capsules can be directly replaced with algae oil capsules,” explains Fredrika. “The marine omega-3 fatty acids DHA and EPA found in microalgae are identical to those found in oily fish. This is because fish obtain their omega-3 from microalgae in the sea.”..."
^ videnskab.dk: Krillolie udfordrer fiskeolie. Ny forskning antyder, at kroppens optag af omega-3 er mere effektivt, når det kommer fra krillolie end fra fiskeolie Citat: "...»Deltagerne i krilloliegruppen fik en lavere dosis omega-3 end deltagerne i fiskeoliegruppen. Alligevel så vi, at mængden af omega-3 i blodet øgedes lige meget for de to grupper,« siger Stine Ulven...Undersøgelsen viser derfor, at både fiskeolie og krillolie er gode kilder til omega-3. »Vi så ingen forskel i sundhedseffekten af fiskeolie og krillolie,« siger Stine Ulven..."
^ Wake Forest Baptist Medical Center (8. juli 2008). "Popular Fish, Tilapia, Contains Potentially Dangerous Fatty Acid Combination". Science Daily. Hentet 2008-07-11.

Se også

Omega-6-fedtsyre

Spire

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[nih-1] ^ ^a ^b ^c ^d ^e ^f nih.gov: Omega-3 Fatty Acids. Fact Sheet for Health Professionals Citat: "...The two major classes of polyunsaturated fatty acids (PUFAs) are the omega-3 and omega-6 fatty acids...Several different omega-3s exist, but the majority of scientific research focuses on three: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)...The human body can only form carbon–carbon double bonds after the 9th carbon from the methyl end of a fatty acid [1]. Therefore, ALA and linoleic acid are considered essential fatty acids, meaning that they must be obtained from the diet [2]. ALA can be converted into EPA and then to DHA, but the conversion (which occurs primarily in the liver) is very limited, with reported rates of less than 15% [3]. Therefore, consuming EPA and DHA directly from foods and/or dietary supplements is the only practical way to increase levels of these fatty acids in the body...ALA is present in plant oils, such as flaxseed, soybean, and canola oils [3]. DHA and EPA are present in fish, fish oils, and krill oils, but they are originally synthesized by microalgae, not by the fish. When fish consume phytoplankton that consumed microalgae, they accumulate the omega-3s in their tissues [3]... Plant oils that contain ALA include flaxseed (linseed), soybean, and canola oils [2,3]. Chia seeds and walnuts also contain ALA...The omega-3 content of fish varies widely. Cold-water fatty fish, such as salmon, mackerel, tuna, herring, and sardines, contain high amounts of LC omega-3s, whereas fish with a lower fat content—such as bass, tilapia and cod—as well as shellfish contain lower levels [3]. The omega-3 content of fish also depends on the composition of the food that the fish consumes [24]. Farmed fish usually have higher levels of EPA and DHA than wild-caught fish, but it depends on the food they are fed [24,25]. An analysis of the fatty acid composition of farm-raised Atlantic salmon from Scotland showed that the EPA and DHA content significantly decreased between 2006 and 2015 due to the replacement of traditional marine ingredients in fish feed with other ingredients [26]. Beef is very low in omega-3s, but beef from grass-fed cows contains somewhat higher levels of omega-3s, mainly as ALA, than that from grain-fed cows [27]...Table 2: Selected Food Sources of ALA, EPA, and DHA [29]...", backup

[2] tdoktor.dk: Fiskeolier (omega-3 fedtsyrer) Citat: "...De egentlige fiskeolier omfatter EPA (eikosa-pentaen-syre) og DHA (dokosa-hexaen-syre). ALA (alfa-linolen-syre) er en omega-3 fedtsyre i planteverdenen, der i mindre grad bliver omdannet til EPA og DHA i vores stofskifte...", backup

[3] "Hemp Oil". InnVista. november 2005. Arkiveret fra originalen 17. september 2012. Hentet 18. november 2006. Citat: "...Hemp seeds are the only natural source to boast of having the ideal ratio of EFAs required by the human body, which is roughly 3:1 of omega-6 to omega-3, the two most important EFAs..."

[4] 4. mar 2013, ing.dk: Svenskere vil presse sunde olier ud af alger og skåne fiskene. Svensk forsker har sprunget fisken over og er gået direkte til kilden i jagten på de sunde omega-3-fedtsyrer. Citat: "...»Men det er de samme nyttige fedtsyrer, DHA og EPA, der findes i algerne, for det er fra algerne, de fede fisk får sin omega-3,« forklarer forskeren..."

[5] Nov 29, 2012, kth.se: Fredrika Gullfot cultivates algae that could replace fish and crude oil Arkiveret 4. juli 2013 hos Wayback Machine Citat: "...“Fish oil capsules can be directly replaced with algae oil capsules,” explains Fredrika. “The marine omega-3 fatty acids DHA and EPA found in microalgae are identical to those found in oily fish. This is because fish obtain their omega-3 from microalgae in the sea.”..."

[6] videnskab.dk: Krillolie udfordrer fiskeolie. Ny forskning antyder, at kroppens optag af omega-3 er mere effektivt, når det kommer fra krillolie end fra fiskeolie Citat: "...»Deltagerne i krilloliegruppen fik en lavere dosis omega-3 end deltagerne i fiskeoliegruppen. Alligevel så vi, at mængden af omega-3 i blodet øgedes lige meget for de to grupper,« siger Stine Ulven...Undersøgelsen viser derfor, at både fiskeolie og krillolie er gode kilder til omega-3. »Vi så ingen forskel i sundhedseffekten af fiskeolie og krillolie,« siger Stine Ulven..."

[Wake-7] Wake Forest Baptist Medical Center (8. juli 2008). "Popular Fish, Tilapia, Contains Potentially Dangerous Fatty Acid Combination". Science Daily. Hentet 2008-07-11.

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