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Health and Disease
"Omega-3 fatty acids"
September 19, 2011
The first speaker of this session was Professor Thomas Sanders (Kings' College London, UK). The title of his presentation was 'the use of alpha-linolenic acid (ALA) and EPA/DHA as dietary sources of omega-3 fatty acids'. The basis for guidelines has shifted from the level of intake needed to prevent deficiency and maintaining normal physiological functions towards the intake that is associated with a decreased risk of chronic diseases. The essentiality of omega-3 fatty acids for this latter recommendation is still under investigation. Especially DHA has an important physiological role in the retina and the brain. Data from meta-analyses show no clear benefit for supplementation with DHA postnatally on visual or cognitive function. Observational studies show a beneficial effect of omega-3 fatty acids on the risk of coronary heart diseases (more consistent for EPA/DHA than for ALA). He concluded that only in the special case of preterm infants an additional amount of DHA is required. Fish consumption is associated with a lower risk of coronary heart disease that appears to be linked to the provision of EPA/DHA. Randomized clinical trials indicate a possible reduction in sudden death with patients with pre-existing coronary heart disease if a daily dose of 0.8 g EPA/DHA is provided.
Then Dr Kathrin Kuhnt (Friedrich-Schiller-University, Germany) gave a presentation of the use of plant-based oils as an alternative source to marine sources. She studied the use of echium oil, a rich source of stearidonic acid (C18:4; the first metabolite after the rate-limiting step of ALA conversion into the longer chain omega-3 fatty acids). The results of an 8 week intervention trial with echium oil supplementation (17 g/d) in three test groups (differing in age and BMI) showed that already after 7 days the fatty acids of echium oil were increased in plasma, erythrocytes and PBMC (peripheral blood mononuclear cell). The content of the longer chain omega-3 fatty acids was increased 2 to 3-fold, with the exception of DHA. The conclusion of this trial is that echium oil can improve the EPA en DPA status in blood. In addition, the concentrations of cardiovascular risk factors were decreased in serum, such as LDL-cholesterol and triacylglycerols, especially in subjects with metabolic syndrome.
Professor Sebastiano Banni (University of Cagliari, Italy) presented the impact of dietary fat on the biosynthesis of endocannabinoids, bioactive lipids that are derived from arachidonic acid in membranes. Results from rat studies showed that the incorporation of omega-3 fatty acids in membranes have an effect on the levels of endocannabinoids. He concluded that the physiological balance of the endocannabinoid system is not modified by dietary saturated fatty acids per se but rather by the dietary ratio of n-6/n-3 PUFAs. This seems to be the key factor for modifying endocannabinoid biosynthesis, thus influencing the onset of the metabolic syndrome and its cardiovascular consequences.
The last speaker of this session on omega-3 fatty acids was Dr Leslie Couëdelo (Bordeaux University, France) who investigated ways to improve the bioavailability of ALA, since the dietary recommendation for this fatty acids are not met in France. She investigated both physical and chemical aspects in rats: the type of the lipid, the deposition of ALA on the glycerol backbone and the provision of ALA emulsified or not. Her conclusion was that the intestinal recovery of ALA was improved by emulsification, but remained unchanged regardless of the Tryacylglycerol (TAG) structure. These data do not exclude the influence of the ALA position in the ingested TAG on its metabolic fate in the organism.
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