4.1. Effects on Fatty Acid Distribution in Erythrocytes in Response to Linseed Oil Supplementation
desaturation
ZINC DEFICIENCY, ZINC DEFICIENCY, IRON DEFICIENCY
An increased amount of EPA and DHA in erythrocytes is associated with reduced cardiovascular risk, which cannot be clearly confirmed for ALA [Our study shows that linseed oil supplementation (10 en%, 22–27 mL ≙ 13–16 g ALA) significantly increases ALA, ETA, and EPA concentrations in erythrocytes in all groups. In contrast, the DHA concentration dropped significantly in the HLA, LLA, and control groups. Since DHA is the most prominent fatty acid in erythrocytes in quantity, the Greupner and Kutzner et al. (2018) observed a significant increase in ALA, EPA, and DPA concentrations and a significant decrease in C-20:3n6, ARA, C-22:4n6, and DHA concentrations due to a daily intake of 13 g ALA for 12 weeks. In contrast to our study, the LA concentration did not increase [In the study of Wilkinson et al. (2005), a 12-week intervention with 15 g ALA per day led to a significant increase in ALA (225%) and EPA (150%) concentrations. Thus, the ALA increase was weaker, but the EPA increase was more pronounced compared to our study. A significant effect on the DHA concentration could not be determined [Even small amounts of ALA can significantly increase EPA concentration in erythrocytes. In a study by Kuhnt et al. (2016), 5 g of ALA per day for 8 weeks increased ALA, EPA, and DPA concentrations by 201, 32, and 12%, respectively. Again, C-20:3n6 (−5%), C-22:5n6 (−4%), and DHA (−10%) concentrations decreased significantly. LA and ARA did not change significantly [Furthermore, it is described in reviews that ALA supplementation leads to an increase in EPA and, in some studies, also to an increase in DPA concentration, but the DHA concentration mostly remains unchanged or even decreases [One reason for the unchanged or falling DHA concentration due to ALA supplementation could be that ∆6 desaturase is needed for the desaturation of ALA into stearidonic acid (C-18:4) and is not available for the last step of DHA formation (desaturation of C-24:5n3 to C-24:6n3) at the same time. Both substrates compete for the same enzyme. However, the ∆6 desaturase has a higher affinity for ALA, so less DHA is produced [In addition to A study on hamsters confirms this assumption. Higher intakes of ALA resulted in lower levels of DHA and ARA in erythrocytes (LA intake unchanged). The LA concentration, however, increased [The characteristic fatty acid intake, which the menu plans should provide, was not reflected by the changes in fatty acid distribution in the erythrocyte lipids.Differences in fatty acid distribution between the diet groups only rarely occurred. Due to the intended intake of sunflower oil in the HLA and olive oil in the LLA group, LA in the HLA and oleic acid in the LLA group should have increased significantly compared to the other three groups [To investigate the influence of sex, EPA status, and the total change in LA throughout the study on ALA conversion, we first observed the influence of these factors in the diet groups. Subsequently, to achieve a larger sample size, the division into the four groups was removed, and an analysis within the subgroups was performed again.While including the diet groups, no sex-specific difference could be found. However, after dissolving the groups, men showed a significantly higher EPA concentration than women. Previous reviews describe a more efficient conversion of ALA into EPA and DHA in women than in men. The reason for this could be a lower β-oxidation rate (women 22% vs. men 33%; measured over 24 h) of ALA and increased activity of desaturases and elongases due to estrogen [The subdivision according to EPA status within diet groups shows that both ETA and EPA increase significantly more in participants with low EPA status (<0.9% FAME) and DHA as well as the Welch et al. (2010) described a higher conversion of ALA into In the analysis for changes in LA throughout the study within the diet groups, only isolated differences were found, so no clear statement can be made.In general, it must be taken into account that only a small sample size was available for some of the calculations, so these results must be critically evaluated.After removing the diet group subdivision, the In rats and pigs, EPA, DPA, and DHA concentrations in liver lipids or plasma phospholipids were found to be lower at higher LA intakes than at lower LA intakes when ALA intake was unchanged [Goyens et al. (2006) showed that in healthy men and women, with the same ALA intake (0.4 en%) but different LA intake (7 vs. 3 en%), EPA in plasma phospholipids increased significantly more with lower LA intake. The decrease in DHA concentration did not differ significantly between the two groups [Rosell et al. (2005) also confirmed in their study that a high LA intake correlates inversely with the EPA and DHA plasma concentration (% of total fatty acids) [When interpreting the results, however, it should be noted that the actual percentage of ALA metabolized to EPA, DPA, and DHA cannot be determined, as we could not conduct our study with marked, stable isotopes. Thus, it cannot be concluded that the LC Tracer studies in men have shown that only 6–8% of the ingested ALA is found as EPA, 4–8% as DPA, and 0–4% as DHA in plasma lipids [In addition to influencing factors like EPA status, sex, or change in LA status, genetic factors, in particular, polymorphisms in the fatty acid desaturase (FADS) and fatty acid elongase (ELOVL) genes, and the transcription factors sterol regulatory element-binding protein-1c (SREBP-1c) and peroxisome proliferator-activated receptor α (PPARα) can also influence the expression of desaturases and elongases and thus the conversion of ALA into LC Whether micronutrient status influences the activity of desaturases has mainly been investigated in rats, so human studies are still required.Rat studies indicate that vitamin A supplementation raises the ∆5 and ∆6 desaturase activity (based on product-to-precursor ratios) but decreases the Fads1 (encode ∆5 desaturase) messenger ribonucleic acid (mRNA) concentration [There are contradictory results regarding the influence of folate and vitamin BIron and zinc are cofactors of desaturases. Therefore, it is plausible that iron and zinc status affect desaturase activities. Zinc deficiency in both rats and humans leads to a decrease in ∆6 desaturase activity. Regarding the ∆5 desaturase activity, rat and human studies show contradictory results. In rats, zinc deficiency leads to a decrease in ∆5 desaturase activity, whereas high serum zinc was associated with low ∆5 desaturase activity in humans. Moreover, iron deficiency impairs LC-PUFA synthesis in rats and humans [