Metabolic impairments associated with type 2 diabetes, including insulin resistance and loss of glycaemic control, disproportionately impact the elderly. Lifestyle interventions, such as manipulation of dietary fat quality (i.e. fatty acid (FA) composition), have been shown to favourably modulate metabolic health. Yet, whether or not chronic consumption of beneficial FAs can protect against metabolic derangements and disease risk during ageing is not well defined. We sought to evaluate whether long-term dietary supplementation of fish-, dairy- or echium-derived FAs to the average FA profile in a U.S. American diet may offset metabolic impairments in males and females during ageing. One-month-old CD-1® mice were fed isoenergetic, high-fat (40 %) diets with the fat content composed of either 100 % control fat blend (CO) or 70 % CO with 30 % fish oil, dairy fat or echium oil for 13 months. Every 3 months, parameters of glucose homoeostasis were evaluated via glucose and insulin tolerance tests. Glucose tolerance improved in males consuming a diet supplemented with fish oil or echium oil as ageing progressed, but not in females. Yet, females were more metabolically protected than males regardless of age. Additionally, Spearman correlations were performed between indices of glucose homoeostasis and previously reported measurements of diet-derived FA content in tissues and colonic bacterial composition, which also revealed sex-specific associations. This study provides evidence that long-term dietary fat quality influences risk factors of metabolic diseases during ageing in a sex-dependent manner; thus, sex is a critical factor to be considered in future dietary strategies to mitigate type 2 diabetes risk.

Vegetable oils containing stearidonic acid (SDA, 18 : 4n-3) are considered better precursors of long-chain n-3 PUFA (LC n-3 PUFA) than those with only α-linolenic acid (ALA, 18 : 3n-3). 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 (n 6) 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 : 5n-3) in meat increased from 6·5 mg 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 : 5n-3), 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 : 6n-3) 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 n-3 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 n-3 PUFA were of little, if any, nutritional significance.

α-Linolenic acid (ALA; 18 : 3n-3) and stearidonic acid (SDA; 18 : 4n-3) are on the biosynthetic pathway of EPA (20 : 5n-3) and DHA (22 : 6n-3). The n-3 fatty acid in rapeseed oil is ALA while Echium oil contains both ALA and SDA. To determine the comparative efficacy of ALA- and SDA-rich oils in enriching broiler meat with n-3 PUFA, we offered diets supplemented with rapeseed oil (rapeseed group) or Echium oil (Echium group) for 35 d to two groups of chicks (age 21 d). There were no differences in carcass weight (2·20 (sem 0·06) v. 2·23 (sem 0·05) kg), boned, skinless thigh muscle (494 (sem 20·5) v. 507 (sem 16·7) g), boned, skinless breast muscle (553 (sem 13·4) v. 546 (sem 11·6) g) or organ weights (heart, liver and gizzard) between the two groups. The total intramuscular fat (IMF) percentage of thigh (8·0 (sem 0·64) v. 8·1 (sem 0·62) %) and breast muscles (2·3 (sem 0·24) v. 2·0 (sem 0·19) %) were also similar between the groups. In contrast, the concentrations of most of the individual n-3 fatty acids (ALA, SDA, EPA and docosapentaenoic acid) were all higher in the Echium than the rapeseed group (P < 0·05). However, differences in DHA concentrations were significant in breast but not thigh muscle IMF. The total n-3 yields/100 g serve thigh muscle were 265 and 676 mg for the rapeseed and Echium groups, respectively (P < 0·0001). The corresponding values for equivalent breast muscles were 70 and 137 mg, respectively (P < 0·01). We conclude that Echium oil is a better lipid supplement than rapeseed oil in changing the concentration and yield of n-3 fatty acids, except DHA, in broiler meat.