Effects of various natural sweeteners on insulin resistance, inflammation and liver steatosis in a rat model of diet‐induced obesity

Background The detrimental effect of refined sugars on health has been the subject of many investigations. However, very few studies have looked at the long‐term beneficial impact of natural sweeteners in a context of obesity. Objective The objective of this study was to compare the metabolic responses following the chronic ingestion of refined simple sugars (sucrose and fructose) to that of various natural sweeteners in a diet‐induced obese insulin‐resistant rat model. Methods Rats were fed a high‐fat high sucrose diet (HFHS) for 8 weeks and received daily gavage with a solution of equivalent amount of total carbohydrates from either sucrose, fructose, maple syrup, molasses, brown rice syrup, agave syrup, corn syrup, or honey. A group fed a standard chow diet receiving daily gavage with the sucrose solution was used as a control. Weekly body weight and food intake were assessed. At week 7, glucose tolerance was evaluated by an oral glucose tolerance test (OGTT), while insulin sensitivity was determined using the HOMA‐IR index at 8 weeks. Nonalcoholic fatty liver disease (NAFLD) was assessed by hepatic triglyceride (TG) content and liver inflammation. Results Daily gavage with the different natural sweeteners did not lead to differences in food intake or body weight gain. During the OGTT, similar glycemic responses were observed across the different treatment groups. However, the insulin excursions were lower in the maple syrup treated animals suggesting improved insulin sensitivity. Assessment of insulin resistance by calculation of the HOMA‐IR index further revealed that all natural sweeteners except corn syrup significantly improved insulin sensitivity, when compared to sucrose treatments. Furthermore, whereas hepatic TG content was reduced in maple syrup, molasses and agave syrup treated rats, there was an increased TG accumulation in the brown rice and corn syrup treated rats. Hepatic inflammation, as revealed by increased IL‐1B levels in obese rat liver, was also reduced to various extents by gavage of molasses, agave syrup, maple syrup and corn syrup. Conclusion Several natural sweeteners used in this study were found to improve insulin sensitivity and to reduce NAFLD as compared to an equivalent amount of sucrose in diet‐induced obese rats. Among the natural sweeteners, maple syrup, molasses and agave syrup appear to exert the most consistent beneficial effects on multiple metabolic health endpoints, suggesting that consumption of those natural sweeteners is a healthier alternative to simple refined sugar. Support or Funding Information This project was supported by Agriculture and Agri‐Food Canada from the Agricultural Innovation program, a federal‐provincial‐ territorial initiative in Canada, and with the participation of the Federation of Quebec Maple Syrup Producers.