Older people with prediabetes who followed a diet rich in sardines for 1 year show significant reductions in risk of developing type 2 diabetes compared with those placed on a similarly healthy diet but without the sardines, results from a new randomized trial show. 

“A 1-year, sardine-enriched type 2 diabetes-preventive diet in an elderly population with prediabetes exerts a greater protective effect against developing type 2 diabetes and cardiovascular events, by improving anthropometric parameters, blood chemistry profile, lipid composition in erythrocytes membranes, and metabolomics data,” report the authors in research published in Clinical Nutrition by Diana Díaz-Rizzolo, PhD, of the Hospital Clinic of Barcelona, Spain, and colleagues.

While cardiovascular and other health benefits of unsaturated fats in oily fish are well-established and are a key component in diets such as the highly recommended Mediterranean diet, the authors note that the consumption of sardines for the prevention of type 2 diabetes has not previously been studied.

In addition to being rich in healthy omega-3 fatty acids, sardines have high concentrations of taurine — approximately 147 mg per 100 g serving — which, depending on the sardine species, is believed to have hypoglycemic, antioxidant, and anti-inflammatory benefits, the authors note.

At 1 year, the percentage of participants classified as being at a very high risk of type 2 diabetes, had declined to a much greater degree in the sardine consumption group compared with those in the control group, who only consumed the nutritional diet.

In addition, those in the sardine group had greater increases in healthy HDL cholesterol and the glucose-regulating protein hormone adiponectin, with decreases in triglycerides compared with the nonsardine group. Furthermore, the sardine consumption group had a greater decrease in insulin resistance.

Sardines Are Cheap and Reduce Blood Pressure Too

“Not only are sardines reasonably priced and easy to find, but they are safe and help to prevent the onset of type 2 diabetes,” said Díaz-Rizzolo in a press statement.

Those in the sardine group also showed significant decreases in systolic blood pressure and diastolic blood pressure, while no significant changes were observed in the control group.

Previously, only lean fish consumption had demonstrated an improvement in blood pressure, not fatty fish consumption, perhaps because the species studied excluded those with a higher taurine content such as sardines.

In addition to showing improvements in levels of taurine, those in the sardine group also showed increases in nutrients that have been linked to health benefits, including omega-3 EPA and DHA, vitamin D, and fluorine

Some Benefits Seen in Both Groups

The patients in the study were a mean age of 71 and had been in a prediabetic state for an average of 4.8 years at the beginning of the study. They were 55% male and there were no other significant differences in characteristics between the groups.

While the conversion from being prediabetic to type 2 diabetes in the adult population has been reported to be about 10.6%, and the risk has been observed to be even higher in the 65 and older population, rates were lower than that in both groups.

Both the sardine consumption and control groups showed significant reductions, as well as significant reductions in glucose fasting concentrations.

Both groups showed improvements in the management of body weight, body mass index, and waist and hip circumference, in addition to improvement in body composition — despite no physical activity components in the programs, the authors note.