Association between interaction and ratio of ω-3 and ω-6 polyunsaturated fatty acid and the metabolic syndrome in adults

January 1, 2012 Human Health and Nutrition Data 0 Comments

Association between interaction and ratio of ω-3 and ω-6 polyunsaturated fatty acid and the metabolic syndrome in adults

Year: 2012
Authors: Mirmiran, P. Hosseinpour-Niazi, S. Naderi, Z. Bahadoran, Z. Sadeghi, M. Azizi, F.
Publication Name: Nutrition
Publication Details: doi:10.1016/j.nut.2011.11.031


Objective: To investigate the association of the intakes of n3 (including alpha linolenic acid [ALA], eicosapentaenoic acid [EPA] plus docosahexaenoic acid [DHA]) and n6 polyunsaturated fatty acids (PUFAs), the interaction, and the ratio of these PUFAs with the metabolic syndrome (MetS) in adults. Methods: This cross-sectional study was conducted in a random sample of participants (n of 2451 and 19 to 84 y old) in the Tehran Lipid Glucose Study. Dietary intake was assessed using a validated semiquantitative food-frequency questionnaire. Anthropometric characteristics, blood pressure, and fasting plasma concentrations of glucose and lipids were measured. The MetS was defined according to the Adult Treatment Panel III guidelines. Results: Among the PUFAs, the ALA and n6 PUFA intakes were inversely associated with the MetS. Subjects in the highest quartile of ALA and n6 fatty acid intakes had a 38% (odds ratio 0.62, 95% confidence interval 0.41�0.95) and a 0.47% (odds ratio 0.53, 95% confidence interval 0.31�0.89) lower prevalence of MetS, respectively, compared with those in the lowest quartile. The dietary ratio of n6 to n3 fatty acids was not associated with the MetS. When the interaction between ALA and n6 fatty acid was assessed, the ALA intake was associated with a lower prevalence of the MetS, without modification by the n6 PUFA intake. Subjects with at least the median ALA intake (1084 mg/d) had a lower prevalence of the MetS, irrespective of an n6 PUFA intake lower or higher than the median compared with subjects with intakes below the median for both. Conclusion: The ALA intake was inversely associated with the MetS, irrespective of the background intake of n6 PUFAs, in adults. (Authors abstract)

The metabolic syndrome (MetS) refers to the constellation of metabolic abnormalities including glucose intolerance, abdominal obesity, dyslipidemia, and hypertension and is associated with an increased risk of cardiovascular disease and diabetes. The n3 PUFAs may decrease the MetS risk as a result of the beneficial effect on insulin resistance, blood pressure, and dyslipidemia. Conversely, n6 PUFAs, which competes with n3 for several physiologic processes, can increase inflammatory eicosanoids. This study was conducted to assess the association between of n6 and n3 PUFAs (alpha linolenic acid [ALA], eicosapentaenoic acid [EPA], and docosahexaenoic acid [DHA]) intakes and the MetS. The present study also aimed at determining whether the background dietary intake of n6 PUFAs modulates the effects of dietary n3 PUFAs on the MetS and its components in 19 to 84 year old subjects. The purpose of the present study was to determine whether the background dietary intake of n6 PUFAs modulates the effects of EPA, DHA and ALA on the risk of the MetS and its components. The findings showed that intakes of EPA � DHA were associated with a lower risk of high serum triacylglycerol concentrations, regardless of the background intake of n6 PUFAs. In addition, the ALA intake with a high or low n6 PUFA intake decreased the risk of an enlarged waist circumference and the MetS. Also, the dietary intake of n6 PUFA decreased the risk for the MetS. The results showed no association between n3 PUFA intake and the n6:n3 ratio and the MetS in Tehranian adults. A tendency toward a lower prevalence of MetS was observed with increasing the intakes of both EPA and DHA. In the present study, an inverse association between ALA intake and the MetS was consistent with other observational prospective cohort studies that showed a beneficial effect of ALA on diabetes and cardiovascular disease. The intake of ALA was 1.2 g/d (median 1084 mg/d), and the findings were in accordance with that of a number of human studies that showed that ALA decreases the risk for coronary heart disease when the intake of n3 PUFA intake is low.  It has been shown that at a low intake of n3
PUFAs, n6 PUFAs are associated with high levels of inflammatory factors, whereas at a high intake of n3 PUFAs, the combination of n6 and n3 PUFAs is related to the lowest levels of inflammation. This inhibitory effect of ALA on the conversion of linoleic acid to arachidonic acid may lead to a suppression of the atherogenic activation of vascular endothelial cells, inhibition of the production of chemokines and interleukins by the endothelial cells of adhesion molecules, and inhibition of the activation of nuclear factor kB in endothelial cells. Therefore, it seems that the amount of ALA intake may determine whether n6 PUFAs are positively or negatively associated with the risk of chronic disease. The results showed that the ALA intake was inversely associated with the risk of MetS independent of the PUFA intake, indicating that the inverse association between the intake of n6 PUFA and the Mets may be modulated by an adequate intake of ALA, an association that needs to be studied further. Future studies using longitudinal data are needed to confirm the results. In addition, the concentrations of free fatty acids that have a strong association with insulin resistance and the MetS were not measured.  In addition, this study included only healthy adults, and thus the findings cannot be extrapolated to other populations. (Editors Comments)

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