Study finds linoleic acid has long-term benefits in diabetes prevention, arachidonic acid not harmful.
Many studies have already investigated the cardiovascular effects of omega-6 fatty acids, but there a few studies on outcomes such as type 2 diabetes. In this study, the researchers did a pooled analysis of new, harmonized, individual-level data within the Fatty Acids and Outcomes Research Consortium. Omega-6 polyunsaturated fatty acids (PUFAs) have some conflicting results. The American Heart Association and Dietary Guidelines for Americans recommend 5-10% of energy be obtained from linoleic acid. But other guidelines such as the French national guidelines recommend limiting linoleic acid consumption to no more than 4% of energy because some researchers hypothesized linoleic acid can have harmful effects since it competes with omega-3 PUFA or arachidonic acid could have harmful effects. Omega-6 fat can be found in nut oils such as soybean and sunflower oil. In this study, they did a harmonized analysis that looked at 20 prospective cohort studies to assess the association between levels of linoleic acid and arachidonic acid biomarkers (omega-6 fatty acids) with incident type 2 diabetes.
The participants in the analysis were 18 years or older; people with type 2 diabetes at baseline were excluded. Incident type 2 diabetes was defined by: fasting glucose concentration of 126 mg/dL or higher, a glucose concentration of 200 mg/dL or higher as measured by a 2 h post-oral glucose tolerance test, new use of insulin or oral hypoglycemic medication, fasting or non-fasting HbA1c concentrations of 6.5% or more, or by self reported physician diagnosis in some cohorts.
The study included 39,740 adults from 20 cohorts in ten countries (United States, Iceland, Netherlands, Germany, Finland, United Kingdom, Sweden, France, Australia and Taiwan). The mean patient age was 49-76 years with body mass index (BMI) of 23.3-28.4 kg/m2 with no type 2 diabetes at baseline. The studies consisted of 17 prospective cohort studies, two prospective case-cohort studies, and one nested case-control cohort study.
The fatty acid biomarkers were measured in phospholipids, total plasma or serum, cholesterol esters, and adipose tissue. During 366,073 person-years, 4,347 participants developed type 2 diabetes. In the pooled analyses, linoleic acid levels were inversely associated with incidence of type 2 diabetes. The associations between linoleic acid and type 2 diabetes were similar in different lipid compartments, which included phospholipids, plasma, cholesterol esters, and adipose tissue. The arachidonic acid biomarkers were not associated with type 2 diabetes. In the categorical analysis, participants in the higher quintiles for linoleic acid biomarkers had a significantly lower risk than participants in the lowest quintile. The linoleic acid levels were associated with a 43% lower relative risk of type 2 diabetes across quintiles in the categorical analysis.
The strengths of this study were the prospective cohorts, use of biomarkers, and large number of participants and events. The limitations of this study were the few data available on adipose tissue, reducing power and precision to assess relevance to type 2 diabetes. Most participants were of European descent, even though there were many ethnicities and races included.
Overall, the study concluded that biomarker levels of linoleic acid, which is a dietary omega-6 PUFA, were inversely associated with the risk of incident type 2 diabetes. Future experimental studies should be done to see the effect of linoleic acid in prevention of type 2 diabetes.
- Arachidonic acid was found not to be associated with type 2 diabetes.
- Participants with higher levels of linoleic acid had less risk of incident type 2 diabetes.
- Study finds linoleic acid has long-term benefits in prevention of type 2 diabetes and arachidonic acid is not harmful.
Wu JHY, Marklund M, Imamura F, et al. Omega-6 fatty acid biomarkers and incident type 2 diabetes: pooled analysis of individual-level data for 39740 adults from prospective cohort studies. The Lancet Diabetes & Endocrinology.2017. (17) 30307-8
Jessica Quach, Doctor of Pharmacy Candidate 2018, GA-PCOM School of Pharmacy