When balanced for precursor fatty acid supply echium oil is not superior to linseed oil in enriching lamb tissues with long-chain n-3 PUFA
When balanced for precursor fatty acid supply echium oil is not superior to linseed oil in enriching lamb tissues with long-chain n-3 PUFA
Year: 2011
Authors: Kitessa, S.M. Young, P. Nattrass, G. Gardner, G. Pearce, K. Pethick, D.W.
Publication Name: British Journal of Nutrition
Publication Details: doi:10.1017/S0007114511005411
Abstract:
Vegetable oils containing stearidonic acid (SDA, 18 4n3) are considered better precursors of long chain n3 PUFA (LC n3 PUFA) than those with only a-linolenic acid (ALA, 18 3n3). The present study re-examined this premise using treatments where added ALA from linseed oil was matched with ALA plus SDA from echium oil. Lambs (n6) were abomasally infused with saline (control (C), 25 ml), echium oil low (EL, 25 ml), echium oil high (EH, 50 ml), linseed oil low (LL, 25 ml) or linseed oil high (LH, 50 ml) for 4 weeks. The basal ration used was identical across all treatments. EPA (20 5n3) in meat increased from 6.5mg in the C lambs to 16.8, 17.7, 13.5 and 11.7 (SEM 0.86) mg/100 g muscle in the EL, EH, LL and LH lambs, respectively. For muscle DPA (docosapentaenoic acid; 22 5n3), the corresponding values were 14.3, 22.2, 18.6, 18.2 and 19.4 (SEM 0.57) mg/100 g muscle. The DHA (22 6n3) content of meat was 5.8 mg/100 g in the C lambs and ranged from 4.53 to 5.46 (SEM 0.27) mg/100 g muscle in the oil infused groups. Total n3 PUFA content of meat (including ALA and SDA) increased from 39 mg to 119, 129, 121 and 150 (SEM 12.3) mg/100 g muscle. We conclude that both oil types were effective in enhancing the EPA and DPA, but not DHA, content of meat. Furthermore, we conclude that, when balanced for precursor n-3 fatty acid supply, differences between linseed oil and echium oil in enriching meat with LC n3 PUFA were of little, if any, nutritional significance. (Authors abstract)
Meat is a major component of the Western-style diet. These investigators argue that increasing the n3 PUFA content of meat needs to be part of the global strategy to minimise the impact of chronic disease. In this study, the objective was to compare the relative efficacy of linseed (flaxseed) oil (with no stearidonic acid (SDA), 18 4n3) and echium oil (SDA 130 mg/g oil) in enriching lamb meat and tissue with EPA and DHA. SDA is the product of delta 6 desaturation of alpha-linolenic acid (ALA), which makes it a step closer to EPA than ALA. Echium oil was found to be more effective than rapeseed oil in enriching poultry meat with EPA and docosapentaenoic acid (DPA). This study aimed to test the efficacy of ALA and SDA containing oils at equal oil volume and equivalent total precursor n3 fatty acid supply. The present study is the first to compare ALA and SDA containing oils on equal total added dietary ALA plus SDA content, as opposed to previous studies where comparisons were based on total oil volume. Across five different tissues (blood, muscle, adipose, heart and liver), it was shown that the gain in enhanced EPA and DHA content due to the use of SDA containing oil, as opposed to ALA only oil, was so small as to be nutritionally relevant. That is, there was no marked difference in the mg of EPA plus DHA per 100 g muscle to be obtained when lambs were supplemented with echium oil as opposed to linseed oil. This conclusion contradicts previous reports where SDA containing oils were reported to be superior to ALA only oils in enriching muscle with LC n3 PUFA (EPA and DHA). The authors suggest that those studies were based on equal oil volume, which entailed markedly different total precursor fatty acid supply. The authors stress that comparisons based on equivalent oil volume with a marked difference in precursor supply exaggerate the efficacy of SDA containing oils in enriching tissue with EPA and DHA. Further research with labelled isotopes is needed to confirm the relative value of SDA containing oils in enriching livestock products with LC n-3 PUFA before such oils can be considered superior to conventional ALA-containing oils. The authors concluded that both linseed oil and echium oil supplementation were similarly effective in enriching lamb meat with LC n3 PUFA. They further recommend that future assessment of precursors of LC n3 PUFA using similar designs should also include isotopes of precursor fatty acids as well as assessment of expressions of genes in the n3 PUFA biosynthetic pathway. (Editors comments)
