The plant-derived α-linolenic acid (ALA) is an essential n-3 acid highly susceptible to oxidation, present in oils of flaxseeds, walnuts, canola, perilla, soy, and chia. After ingestion, it can be incorporated in to body lipid pools (particularly triglycerides and phospholipid membranes), and then endogenously metabolized through desaturation, elongation, and peroxisome oxidation to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), with a very limited efficiency (particularly for DHA), beta-oxidized as an energy source, or directly metabolized to C18-oxilipins. At this moment, data in the literature about the effects of ALA supplementation on metabolic syndrome (MetS) in humans are inconsistent, indicating no effects or some positive effects on all MetS components (abdominal obesity, dyslipidemia, impaired insulin sensitivity and glucoregulation, blood pressure, and liver steatosis). The major effects of ALA on MetS seem to be through its conversion to more potent EPA and DHA, the impact on the n-3/n-6 ratio, and the consecutive effects on the formation of oxylipins and endocannabinoids, inflammation, insulin sensitivity, and insulin secretion, as well as adipocyte and hepatocytes function. It is important to distinguish the direct effects of ALA from the effects of EPA and DHA metabolites. This review summarizes the most recent findings on this topic and discusses the possible mechanisms.

Background/Objectives: This research aimed to investigate phospholipid fatty acid (PLFA) distribution in the brain, kidneys, and white adipose tissue (WAT) and lipid profiles in response to high-fat diets. Methods: Adult female C57BL/6 mice were fed high-fat diets containing 25% linseed, palm, or sunflower oil for 100 days. The fatty acid composition of dietary oils and tissue PL were analyzed using gas–liquid chromatography. Results: Linseed oil increased n-3 polyunsaturated fatty acids (PUFAs) with subsequent conversion into long-chain n-3 PUFAs in the brain and kidney PL, while only alpha-linolenic acid was elevated in WAT. Palm and sunflower oils resulted in unique PLFA distributions in the kidneys and WAT. Palm oil raised linoleic acid without conversion to pro-inflammatory n-6 PUFAs. Sunflower oil increased saturated palmitic acid, as opposed to the rise in monounsaturated oleic acid. Linseed oil also significantly improved lipid profiles, reducing LDL and increasing HDL levels while enhancing cardiovascular indices. Conclusions: This study demonstrates that dietary oils significantly impact organ-specific PLFA profiles, with linseed oil enriching brain and renal n-3 PUFAs, while palm and sunflower oils induce distinct modifications in the kidney and WAT. Moreover, linseed oil offers notable cardioprotective benefits due to the favorable lipid profile changes. These findings highlight the importance of dietary fat selection in achieving balanced lipid metabolism and suggest that diverse oil combinations may be essential for optimizing health outcomes.

Background: The fatty acid profiles in cellular membranes can be influenced by many endogenic and external factors, including diet. They are also associated with numerous metabolic and health conditions, including cardiovascular diseases and inflammation. Objective: This study provides a comparative analysis of the fatty acid profiles in subjects on vegetarian and omnivorous diets. Methods: The study enrolled 152 apparently healthy subjects, comprising 78 omnivores and 74 individuals who had followed a vegetarian diet for a minimum of 2 years, including 61 vegans and 13 lacto-ovo vegetarians. The subjects in the omnivore and vegetarian groups were matched by gender, age, and body mass index (BMI). The composition of the fatty acids in their erythrocyte membranes was determined using gas–liquid chromatography and presented as a percentage of total fatty acids. Results: The study revealed statistically significant differences in the fatty acid profiles: vegetarians had higher levels of oleic acid (OA, 18:1 n-9) (p < 0.001) and linoleic acid (LA, 18:2 n-6) (p < 0.001), while at the same time having lower levels of gamma-linolenic acid (GLA, 18:3 n-6) (p < 0.05), eicosapentaenoic acid (EPA, 22:5 n-3) (p < 0.001), docosapentaenoic acid (DPA, 22:5 n-3) (p < 0.001), docosahexaenoic acid (DHA, 22:6 n-3) (p < 0.001), and total omega-3 polyunsaturated fatty acid (PUFA) (p < 0.001) and a lower omega-3 index (p < 0.001). Additionally, they had lower omega-3 to omega-6 PUFA (p < 0.001); EPA/arachidonic acid (ARA, 20:4 n-6) (p < 0.001); and DHA/ARA ratios (p < 0.001). The activity of delta-6 desaturases (D6D), estimated as the GLA/LA ratio, was higher in the omnivores (p < 0.005), while the activity of elongase 2 (ELOV2), estimated as the DPA/EPA ratio, was higher in the vegetarians (p < 0.005). Most of the differences presented in both vegans and vegetarians, except for GLA and D6D, where differences were observed only in vegans compared to omnivores. Discussion: This study highlights the distinct fatty acid profiles associated with vegan, lacto-ovo vegetarian, and omnivorous diets, suggesting their differential impact on inflammation, disease protection, and overall health. Understanding the implications of the fatty acid profiles within these dietary patterns can be used for personalized nutritional recommendations and supplementation for individuals adhering to specific dietary lifestyles.