Impact of Fatty Fish on Post-Meal Glucose Regulation

Study Overview

A compelling new study has demonstrated that consuming fatty fish, such as salmon, significantly enhances post-meal glucose regulation compared to lean fish like cod or no fish consumption at all. Participants who included salmon in their diet five times a week exhibited a notable reduction in post-meal blood glucose levels after an eight-week period, in contrast to baseline measurements and those consuming cod or no fish.

Background on Fish Consumption and Diabetes Risk

Previous observational studies have suggested a protective effect of fish consumption against type 2 diabetes mellitus. However, long-term research has produced mixed results regarding the correlation between fish intake and the incidence of type 2 diabetes. Some studies indicated an increased risk, others found no significant impact, while a few suggested a decreased risk. A crucial factor often overlooked in these studies is the type of fish consumed. The omega-3 polyunsaturated fatty acids (PUFAs), specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) present in fatty fish, are believed to be converted into anti-inflammatory molecules, potentially reducing the risk of type 2 diabetes.

Details of the New Study

Published in the British Journal of Nutrition in May 2017, this recent study involved 68 healthy overweight or obese Caucasian individuals (BMI ≥ 27 kg/m²), aged between 36.2 and 53.2 years. Conducted at Haukeland University Hospital in Bergen, Norway, the participants were divided into three groups: one consuming 750 g of cod (lean fish) weekly, another consuming 750 g of salmon (fatty fish), and a control group that did not eat fish.

Each group was instructed to include 150 g of fish in five dinners per week, avoiding other seafood for the study’s duration. Blood samples were collected at baseline and again after eight weeks, measuring glucose, C-reactive protein (CRP), insulin, insulin C-peptide, and various inflammatory markers.

Findings of the Study

At baseline, there were no significant differences in fasting glucose, insulin, or insulin C-peptide levels among the groups. After eight weeks, the salmon group showed a significantly lower post-meal increase in glucose levels at 90 and 120 minutes post-breakfast compared to the no-fish control group. The cod group did not exhibit any notable differences relative to the control group. Additionally, the intake of fatty fish resulted in a small yet statistically significant rise in insulin C-peptide concentration at 120 minutes after breakfast.

The salmon group also experienced an increase in omega-3 PUFAs and a decrease in omega-6 PUFAs in their serum leucocytes compared to the cod and control groups. Conversely, cod consumption led to a rise in DHA content in leucocytes when compared to the control group. There were no significant differences in chemotaxis or bacterial ingestion abilities among the leucocytes from the different groups. Blood levels of inflammatory markers, including CRP, IL-1b, IL-6, IL-8, MCP-1, and TNFα, showed no significant variation.

Limitations of the Study

One notable limitation of the study is the reliance on participant-reported compliance with dietary requirements, which was not independently verified. Additionally, the study did not account for the effects of other dietary components or food preparation methods. Although participants reported no significant changes in overall energy and macronutrient intake, the assumption was made that any health benefits were attributable solely to fish consumption.

Conclusion

This study suggests that incorporating fatty fish—such as salmon, sardines, mackerel, herring, and anchovies—into the diet may offer protective benefits against the onset of type 2 diabetes in overweight or obese individuals. The results indicate that fatty fish consumption does not significantly elevate insulin or insulin C-peptide levels after eight weeks, implying that improvements in post-meal glucose control may stem from enhanced insulin sensitivity and glucose regulation.

Written By: Usha B. Nair, Ph.D.