Dietary ω-3 fatty acid and ω-3: ω-6 fatty acid ratio predict improvement in glucose disturbances in Japanese Brazilians

Objective: We investigated whether lifestyle-induced changes in dietary fat quality are related to improvements on glucose metabolism disturbances in Japanese Brazilians at high risk of type 2 diabetes. Methods: One hundred forty eight first and second generation subjects with impaired glucose tolerance or impaired fasting glycemia who attended a lifestyle intervention program for 12 months were studied in the city of Bauru, State of Sao Paulo, Brazil. Dietary fatty acid intakes at baseline and after 12 months were estimated using three 24h recalls. The effect of dietary fat intake on glucose metabolism was investigated by multiple logistic regression models. Results: At baseline, mean 6 standard deviation age and body mass index were 60 plus and minus 11 y and 25.5 plus and minus 4.2 kg/m2, respectively. After 12 mo, 92 subjects had normal plasma glucose levels and 56 remained in prediabetic conditions. Using logistic regression models adjusted for age, gender, generation, basal intake of explanatory nutrient, energy intake, physical activity, and waist circumference, the odds ratios (95% confidence intervals) for reversion to normoglycemia were 3.14 (1.22�8.10) in the second tertile of total n3 fatty acid, 4.26 (1.34 to13.57) in the second tertile of eicosapentaenoic acid, and 2.80 (1.10 to 7.10) in the second tertile of linolenic acid. Similarly, subjects in the highest tertile of n3:n6 fatty acid ratio showed a higher chance of improving glucose disturbances (2.51, 1.01 to 6.37). Conclusions: Our findings support the evidence of an independent protective effect of n3 fatty acid and of a higher n3:n6 fatty acid ratio on the glucose metabolism of high risk individuals. (Authors abstract)

Recent trials have strongly suggested that type 2 diabetes can be prevented by the adoption of a healthy lifestyle in subjects with impaired glucose tolerance.  The hypothesis of the present study was that changes in dietary intake could predict improvement in glucose metabolism. The relation between dietary fatty acids, especially n3 fatty acids and the n3:n6 ratio, to improvements in glucose tolerance status after a 12 mo lifestyle intervention was investigated in Japanese Brazilians at high risk of type 2 diabetes at baseline. This prospective investigation revealed that a moderate intake of dietary n3 fatty acids, EPA, and ALA and diets with a higher n3:n6 fatty acid ratio in Japanese Brazilians on prediabetic states were independently associated with achieving normoglycemic blood glucose levels after 12 mo of lifestyle intervention. A higher increase in dietary n3 fatty acids, ALA, EPA, and n3:n6 fatty acid ratio after 12 mo predicted higher chances of achieving normoglycemic blood glucose levels. Randomized clinical trials will be necessary to elucidate the underlying mechanisms of the improvements in glucose metabolism.  The present results show the relevance of quality rather than quantity of dietary fats on the improvement of glucose metabolism. No relation among docosahexaenoic acid, EPA/arachidonic acid ratio, and improved glucose metabolism was verified. It is important to note that the present study was a food-based intervention. Individuals were also encouraged to increase the intake of nuts and plant sources of n3 fatty acids. Differential intakes of dietary fat subtypes may affect diabetes risk by modifying the phospholipid composition of cell membranes. This effect may play a role in blood glucose regulation through action on insulin secretion and insulin receptor properties which is in line with the greater chance of developing normoglycemic blood glucose levels in individuals in the highest ratios of n3:n6 fatty acids after a lifestyle intervention shown in the present study. The authors suggest that these results may contribute toward unraveling the physiologic effects of fatty acids on glucose metabolism. (Editors comments)