Perhaps other omega3 oils are better than fish oil.
Background  Nearly 12% of US adults have type 2  diabetes, a prevalence 25% greater than that reported only 20 y ago.  Although the nation's                   battles with caloric overconsumption and obesity are  largely to blame, some research suggests that a shift in the types of                   dietary fats might also be involved. Of particular  interest is the well-documented inverse relation between fish oil  consumption                   and diabetes risk. Not all research, however, is  consistent in this regard, with some showing increasing risk with  greater                   consumption of the long-chain, omega-3 fatty acids  typically found in marine foods. Three independent studies, accompanied                   by a corresponding editorial by Edith Feskens from  Wageningen University, published in the August 2011 issue of 
The American Journal of Clinical Nutrition contribute new insight into how consumption of various omega-3 fatty acids might be related to diabetes risk. 
                
Study Design  Two of the  investigations were conducted in Chinese populations�one using data from  the Singapore Chinese Health Study (43,176                   men and women), the other from the Shanghai Health  Studies (116,156 men and women). Whereas the Singapore study related  total                   omega-3, nonmarine-derived omega-3, and  seafood-derived omega-3 intake with risk of diabetes, the Shanghai study  compared                   intakes of various types of seafood and total omega-3  intake with diabetes risk. The third study, based in the United States,                   followed a cohort of adults (3088 men and women);  blood concentrations of various seafood- and plant-based omega-3 fatty  acids                   were studied in regard to their association with  diabetes risk. 
                
Results  The Singapore study  documented an inverse relation between plant-derived omega-3 intake, but  not seafood-derived omega-3                   intake, and risk of diabetes. Data from the Shanghai  cohort suggested decreased diabetes risk with increased seafood intake,                   although the relation was stronger for women than men.  Results from the US cohort suggested that several forms (marine and                   plant) of omega-3 fats were related to lower risk of  diabetes. 
                
Conclusions  In her accompanying  editorial, Feskens queries, "in the prevention of type 2 diabetes:  should we recommend vegetables oils                   instead of fatty fish?" Indeed, plant-based omega-3  fatty acids (such as alpha-linolenic acid, a dietary essential) have  been                   shown in numerous studies to be as inversely related  to diabetes risk, if not more so, as marine oils. She also urges  additional                   research using fatty acid intake biomarkers and  further investigation of the inherent interactions between genetics and  diet                   on diabetes incidence and progression.                                   
https://www.ajcn.org/site/misc/release3.xhtml#bros