# Erythrocyte Phospholipid Fatty Acid Profile in High-Level Endurance Runners
## 4 Discussion
mentioned earlier, \(\omega\)-3 and \(\omega\)-6 PUFA compete for the same enzymatic pathways for their incorporation into the cell membrane [12]. In a previous study, [PERSON] et al. [40] found a negative relationship between AA concentrations and EPA and DHA in erythrocytes. Therefore, an \(\omega\)-3 deficiency leads to increased AA incorporation into the erythrocyte. Ultra-processed foods intake, ready to consume and hyperpalatable, has increased in the last years and is associated with poorer diet quality [41]. [PERSON] et al. [23] indicated that athletes were not consuming the recommended amount of \(\omega\)-3 in their diet. Oily fish (salmon, sardines, shrimp...) are rich sources of \(\omega\)-3. The main barriers athletes encounter in consuming oily fish are its smell and taste. EPA and DHA are essential \(\omega\)-3 PUFAs in the lipid bilayers of erythrocyte membranes [42]. In our study, significantly higher EPA levels were observed in EG compared to CG. EPA has been documented as an essential FA that helps improve cardiovascular health by reducing blood triglycerides and blood pressure [43]. EPA has also been reported to improve the fluidity and flexibility of the cell membrane, enhancing oxygen diffusion and nutrient delivery to the muscle during physical exercise [44]. These benefits are essential in endurance runners who need to optimize their cardiovascular system for optimal performance. The EG group reported significantly lower DHA levels than the CG. Additionally, the runners had lower values compared to reference indices. DHA deficits have been documented in athletes from different specialties [20; 21; 22; 37; 45]. Physical exercise increases the amount of free radicals and reactive oxygen species (ROS) [16]. This increase in ROS leads to an increase in inflammatory cytokines such as TNF-alpha, IL1, IL6, and IL10 that must be balanced by anti-inflammatory systems [46]. DHA has been documented as an FA that reduces lipid peroxidation and erythrocyte damage in a group of athletes as a result of improved superoxide dismutase activity [6]. In this sense, lower DHA concentrations in runners would be a consequence of increased utilization to balance the excess ROS and free radicals produced by training. In this same vein, [PERSON] et al. [47] observed in a previous study that DHA is a more effective \(\omega\)-3 PUFA than EPA in modulating inflammatory states. There were also significantly higher concentrations of DPA in runners compared to CG. DPA plays a fundamental role in resolving inflammatory processes and regulating the immune system [48]. It has recently been reported that the specialized proresolving mediator RvD5 n3 DPA can be biosynthesized from DPA when elevated concentrations are available, helping to reduce inflammation [49]. EG reported higher SFAs erythrocyte concentrations of total SFA, PA, and SA than CG. Skeletal muscle uses FAs mainly along with triglycerides as fuel during aerobic exercise [10]. It is known that aerobic training improves insulin sensitivity and FA oxidation [43]. Additionally, it has been documented that the body prioritizes the oxidation of PUFAs as an energy fuel over SFAs during aerobic exercise [50]. Consequently, an increased incorporation of SFAs into membrane erythrocyte occurs as a result of the higher PUFAs oxidation during training sessions in EG. Similarly to our study, higher percentages of SA and PA were reported in endurance runners and athletes of different sports compared to CG [27; 37; 51]. In this line, a previous study found a positive correlation between SA concentrations with training aerobic volume [52]. Increased incorporation of SA and PA into the erythrocyte membrane have been demonstrated to enhance stiffness while concurrently reducing permeability [26]. This adaptation may be a toll to pay, resulting in enhanced membrane stability and a reduced peroxidation index. EG showed higher percentages of total MUFA and OA than the CG. The concentrations reported in our runners are similar to those of other groups of athletes [20; 21; 37].