At estimated biologically equivalent intakes, dietary ALA and EPA+DHA have different physiologic effects.

Effect of altered dietary n-3 fatty acid intake upon plasma lipid fatty acid composition, conversion of [13 C]a-linolenic acid to longer-chain fatty acids and partitioning towards b-oxidation in older men The effect of increased dietary intakes of a-linolenic acid (ALNA) or eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 2 months upon plasma lipid composition and capacity for conversion of ALNA to longer-chain metabolites was investigated in healthy men (52 (SD 12) years). After a 4-week baseline period when the subjects substituted a control spread, a test meal containing [U-13 C]ALNA (700 mg) was consumed to measure conversion to EPA, docosapentaenoic acid (DPA) and DHA over 48 h. Subjects were then randomised to one of three groups for 8 weeks before repeating the tracer study: (1) continued on same intake (control, n 5); (2) increased ALNA intake (10 g/d, n 4); (3) increased EPAþDHA intake (1·5 g/d, n 5). At baseline, apparent fractional conversion of labelled ALNA was: EPA 2·80, DPA 1·20 and DHA 0·04 %. After 8 weeks on the control diet, plasma lipid composition and [ 13 C]ALNA conversion to DHA was unchanged. The dietary interventions did not alter partitioning of ALNA towards b-oxidation. The present results indicate ALNA conversion was down-regulated by increased product (EPAþDHA) availability, but was not up-regulated by increased substrate (ALNA) consumption. This suggests regulation of ALNA conversion may limit the influence of variations in dietary n-3 fatty acid intake on plasma lipid compositions.

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Variations in the fatty acid composition of PBMC phospholipids account for some of the variability in immune cell functions among healthy adults.

The UK Food Standards Agency convened a group of expert scientists to review current research investigating whether n-3 polyunsaturated fatty acids (PUFA) from plant oils (a-linolenic acid; ALA) were as beneficial to cardiovascular health as the n-3 PUFA from the marine oils, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The workshop also aimed to establish priorities for future research. Dietary intake of ALA has been associated with a beneficial effect on CHD; however, the results from studies investigating the effects of ALA supplementation on CHD risk factors have proved equivocal. The studies presented as part of the present workshop suggested little, if any, benefit of ALA, relative to linoleic acid, on risk factors for cardiovascular disease; the effects observed with fish-oil supplementation were not replicated by ALA supplementation. There is a need, therefore, to first prove the efficacy of ALA supplementation on cardiovascular disease, before further investigating effects on cardiovascular risk factors. The workshop considered that a beneficial effect of ALA on the secondary prevention of CHD still needed to be established, and there was no reason to look further at existing CHD risk factors in relation to ALA supplementation. The workshop also highlighted the possibility of feeding livestock ALA-rich oils to provide a means of increasing the dietary intake in human consumers of EPA and DHA. a-Linolenic acid: Fish oils: Cardiovascular disease: Nutrition researchThe Food Standards Agency (FSA) convened a workshop on 18 March 2002, to examine the role of a-linolenic acid (ALA) in relation to cardiovascular disease. The results from recently completed studies were presented, both FSA-and non-FSA-funded, and the workshop was chaired by Professor Martijn Katan, Wageningen University, The Netherlands. The aim of the workshop was to determine where this work has taken us and where further work should be concentrated, as well as acting as a vehicle for dissemination. The research recommendations emanating from the workshop discussions will feed into the future direction of the UK FSA-funded nutrition research, and may also be of value in guiding other funders internationally. BackgroundThe long chain n-3 polyunsaturated fatty acids (PUFA), eicosapentanoic acid (EPA; 20 : 5n-3) and docosahexaenoic * (GISSI-Prevenzione Investigators, 1999). EPA and DHA also have a variety of beneficial effects on risk factors for CHD. Oily fish is the richest dietary source of EPA and DHA, but fish consumption is low in habitual UK diets (Department of the Environment, Food and Rural Affairs, 2001). An alternative source of n-3 PUFA is the more abundant ALA (18 : 3n-3), which can be elongated and desaturated to its long-chain derivatives EPA and DHA; however, in man the extent and regulation of this conversion is unclear. The question arises, therefore, whether plant oils rich in ALA (for example, linseed, rapeseed and nut oils) could reproduce the beneficial effects of fish consumption on risk for cardiovascular...

The data suggest that optimal glucose dosage may differ under different conditions of depleted blood glucose resources. In addition, glucoregulation was observed to be a moderating factor. However, further research is needed to develop a model of the moderating and mediating factors under which glucose facilitation is best achieved.

It has been suggested that the memory enhancing effect of glucose follows an inverted U-shaped curve, with 25 g resulting in optimal facilitation in healthy young adults. The aim of this study was to further investigate the dose dependency of the glucose facilitation effect in this population across different memory domains and to assess moderation by interindividual differences in glucose regulation and weight. Following a double-blind, repeated measures design, 30 participants were administered drinks containing five different doses of glucose (0 g, 15 g, 25 g, 50 g, and 60 g) and were tested across a range of memory tasks. Glycaemic response and changes in mood state were assessed following drink administration. Analysis of the data showed that glucose administration did not affect mood, but significant glucose facilitation of several memory tasks was observed. However, dose-response curves differed depending on the memory task with only performance on the long-term memory tasks adhering largely to the previously observed inverted U-shaped dose-response curve. Moderation of the response profiles by interindividual differences in glucose regulation and weight was observed. The current data suggest that dose-response function and optimal dose might depend on cognitive domain and are moderated by interindividual differences in glucose regulation and weight.

BackgroundThere is a metabolic pathway by which mammals can convert the omega-3 (n-3) essential fatty acid α-linolenic acid (ALA) into longer-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). As far as we know there are currently no studies that have specifically examined sex differences in the LC n-3 PUFA response to increased dietary ALA intake in humans, although acute studies with isotope-labelled ALA identified that women have a significantly greater capacity to synthesise EPA and DHA from ALA compared to men.FindingsAvailable data from a placebo-controlled, randomised study were re-examined to identify whether there are sex differences in the LC n-3 PUFA response to increased dietary ALA intake in humans. There was a significant difference between sexes in the response to increased dietary ALA, with women having a significantly greater increase in the EPA content of plasma phospholipids (mean +2.0% of total fatty acids) after six months of an ALA-rich diet compared to men (mean +0.7%, P = 0.039). Age and BMI were identified as predictors of response to dietary ALA among women.ConclusionsWomen show a greater increase in circulating EPA than men during increased dietary ALA consumption. Further understanding of individual variation in the response to dietary ALA could inform nutrition advice, with recommendations being specifically tailored according to habitual diet, sex, age and BMI.