Type 2 diabetes is a disease that is thought to results primarily from lifestyle factors relating to diet and exercise. The cornerstone of type 2 diabetes control and treatment is dietary modifications that replaces poor quality dietary foodstuffs with items of higher quality. Replacing simple sugars (particularly fructose) with complex carbohydrates, increased consumption of plant foods rich in antioxidants, ensuring adequate intakes of vitamins and minerals, and higher intakes of both soluble and insoluble fibre have shown benefits in reducing the symptoms of type 2 diabetes. Less well researched has been the effects of the omega 3 (n-3) marine oils eicosapentanoic acid (EPA, C20:5 (n-3)) and docosahexanoic acid (DHA, C22:6 (n-3)), and the vegetable long chain fatty acid α-linolenic acid (ALA, C18:3 (n-3)). More recent and thorough research is starting to show that increased consumption of these n-3 oils is protective of type 2 diabetes.
Epidemiological research using estimates of n-3 oil consumption to investigate associations with diabetes has been inconclusive, probably because of the difficulty of accurately estimating fish and oil consumption. Because of these problems, researchers1 have used a prospective study design to analyse the plasma phospholipid n-3 fatty acid content of 3088 older men. In a follow-up after 10.6 years, 204 new cases of diabetes had occurred. Analysis of the data using multivariate analysis and controlling for known risk factors showed that those individuals with the highest concentrations of EPA plus DHA or ALA in their phospholipids had the lowest incidence of diabetes. Interestingly, when the researchers analysed the associations of fatty fish and dietary EPA plus DHA, they found no associations with diabetes, which supports the contention that the reporting of fish oil intakes may not be accurate in some types of study.
Fatty fish and fish oils have been shown to be more efficient at increasing the EPA and DHA content of phospholipids compared to vegetable sources of n-3 oils. Although ALA can be converted to EPA and DHA, the conversion is humans is not efficient due to genetic deficiency of one the necessary desaturase enzymes. However, in this study high concentrations of ALA in phospholipids were associated with reductions in the risk of developing diabetes, suggesting that either conversion is adequate or that ALA is protective independent of the conversion to EPA and DHA. Other studues2 have reported strong inverse association between total n-3 fatty acid intake or non-marine sources of long chain fatty acids (ALA) and a decreased risk of diabetes in Chinese Singaporeans. Taken as a whole this suggests that n-3 fatty acids may be protective of diabetes, possibly because of their blood glucose and insulin lowering effects.
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