The essential omega-3 fatty acid alpha-linolenic acid (ALA, 18:3n3) can be converted into EPA and DHA. The aim of the present study was to determine the effect of a high-ALA diet on EPA and DHA levels in red blood cells (RBCs) and their oxylipins in the plasma of subjects with a low EPA and DHA status. Fatty acid concentrations [μg mL] and relative amounts [% of total fatty acids] in the RBCs of 19 healthy men (mean age 26.4 ± 4.6 years) were analyzed by means of GC-FID. Free plasma oxylipin concentrations were determined by LC-MS based targeted metabolomics. Samples were collected and analyzed at baseline (week 0) and after 1 (week 1), 3 (week 3), 6 (week 6), and 12 (week 12) weeks of high dietary ALA intake (14.0 ± 0.45 g day). ALA concentrations significantly (p < 0.001) increased from 1.44 ± 0.10 (week 0) to 4.65 ± 0.22 (week 1), 5.47 ± 0.23 (week 3), 6.25 ± 0.24 (week 6), and 5.80 ± 0.28 (week 12) μg mL. EPA concentrations increased from 6.13 ± 0.51 (week 0) to 7.33 ± 0.33 (week 1), 8.38 ± 0.42 (p = 0.021, week 3), 10.9 ± 0.67 (p < 0.001, week 6), and 11.0 ± 0.64 (p < 0.001, week 12) μg mL. DHA concentrations unexpectedly decreased from 41.0 ± 1.93 (week 0) to 37.0 ± 1.32 (week 1), 36.1 ± 1.37 (week 3), 35.1 ± 1.06 (p = 0.010, week 6), and 30.4 ± 1.09 (p < 0.001, week 12) μg mL. Relative ΣEPA + DHA amounts were unchanged during the intervention (week 0: 4.63 ± 0.19, week 1: 4.67 ± 0.16, week 3: 4.61 ± 0.13, week 6: 4.73 ± 0.15, week 12: 4.52 ± 0.11). ALA- and EPA-derived hydroxy- and dihydroxy-PUFA increased similarly to their PUFA precursors, although in the case of ALA-derived oxylipins, the concentrations increased less rapidly and to a lesser extent compared to the concentrations of their precursor FA. LA-derived oxylipins remained unchanged and arachidonic acid and DHA oxylipin concentrations were not significantly changed. Our results confirm that the intake of ALA is not a sufficient source for the increase of EPA + DHA in subjects on a Western diet. Specifically, a high-ALA diet results in increased EPA and declined DHA concentrations. However, the changes effectively balance each other out so that ΣEPA + DHA in RBCs - which is an established marker for health protective effects of omega-3-PUFA - remains constant. The PUFA levels in RBCs reflect the concentration and its changes in plasma hydroxy- and dihydroxy-PUFA concentrations for ALA and EPA.

Given an equivalent bioavailability of calcium in all test products, neither a high concentration of SO or of HCO influenced the bioavailability of calcium. Accordingly, the use of mineral water with high concentrations of calcium constitutes a calorie-free calcium source that can improve calcium supply.

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aThere is a debate about the optimal dietary ratio of the parent n6 fatty acid linoleic acid (LA) and n3 fatty acid alpha-linolenic acid (ALA) to promote an efficient conversion of ALA to EPA and DHA, which have implications for human health. The aim of the present study was to compare the effects of a low-LA/ high-ALA ( lo LA/ hi ALA) diet with a high-LA/low-ALA ( hi LA/ lo ALA) diet on fatty acid concentrations in red blood cells (RBCs). Fifteen omnivore healthy men (mean age 26.1 ± 4.5 years) with a low initial EPA/DHA status (sum (∑) EPA + DHA% of total fatty acids in RBC at baseline: 4.03 ± 0.17) received both diets for two weeks with a nine-week wash-out phase in between. Fatty acid intake of the subjects was tightly unaffected. The hi LA/ lo ALA diet led to slightly decreased EPA concentrations, while all other fatty acid concentrations remained constant. Compared to our previous study, where we simply increased the ALA intake, our results show that ALA supplementation combined with a reduced LA intake ( lo LA/ hi ALA diet) more efficiently enhanced EPA blood concentrations. The absence of changes in the PUFA pattern in consequence of a LA/ALA ratio of 25.6 ± 2.41 : 1 suggests that the high LA/ALA ratio of the Western diet already leads to a saturation and a further increase of the ratio does not affect the PUFA pattern.

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