Eating two tins of sardines a week may reduce a person's risk of developing type 2 diabetes, research suggests.
The oily fish is known to contain good fats that promote heart health, however, the benefits may not stop there.
Scientists from the Open University of Catalonia in Barcelona analysed 152 people aged 65 or over with prediabetes, when a person's blood sugar level is consistently high but not severely enough to be defined as diabetes.
All the participants were put on the same diabetes-prevention eating plan, however, half also added 200g – around two tins – of sardines in olive oil to their weekly diet.
A year later, the sardine-eating participants were significantly less likely to still be at high risk of type 2 diabetes.
The affordable store cupboard staple is rich in an array of nutrients – including omega-3 fatty acids, calcium and vitamin D – which may ward off the disease.
"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 study author Dr Diana Rizzolo.
"This is a huge scientific discovery. It is easy to recommend this food during medical check-ups and it is widely accepted by the population."
In the UK alone, 3.9 million people have been diagnosed with diabetes, of whom around 90% have type 2.
Type 2 diabetes' onset is often linked to a patient's lifestyle, like carrying excess weight or being too sedentary.
Left untreated, the condition can lead to heart disease, blindness and even limb amputations.
The 152 participants had a fasting glucose level of 100mg/dL to 124mg/dL. This is measured after an individual has not eaten or drank, aside from water, for eight hours. Prediabetes is defined as 100mg/dL to 125mg/dL.
The participants were put on a diet that is known to reduce a susceptible person's risk of developing type 2 diabetes, with 75 also being told to eat sardines.
The fish was generally eaten whole, including its soft bones, to maximise absorption of calcium and vitamin D.
At the start of the study, 27% of the 77 participants in the non-sardine group were deemed to be at particularly high risk of developing type 2 diabetes via the Finnish assessment calculator FINDRISC.
One year later, this had reduced to 22%, as published in the journal Clinical Nutrition.
In the sardine group, 37% were at high risk of type 2 diabetes at the start of the study, down to just 8% after 12 months of regularly eating the oily fish.
Consuming sardines was also linked to higher levels of "good" cholesterol and the hormone adiponectin, which "appears to play a crucial role in protecting against diabetes".
It was also associated with lower blood pressure and reduced amounts of circulating fat in the participants' blood.
Watch: Eating well in middle age wards off type 2 diabetes in later life
The Catalonia scientists specifically analysed people over 65 due to the risk of type 2 diabetes rising in old age.
"As we get older, restrictive diets (in terms of calories or food groups) can help to prevent the onset of diabetes, however, the cost-benefit ratio is not always positive, as we found in other studies," said Dr Rizzolo.
"The results lead us to believe we could obtain an equally significant preventive effect in the younger population."
While sardines are rich in an array of nutrients, the scientists have stressed taking these as supplements may not reap the same benefits.
"Nutrients can play an essential role in the prevention and treatment of many different pathologies, but their effect is usually caused by the synergy that exists between them and the food that they are contained in," said Dr Rizzolo.
"Sardines will therefore have a protective element because they are rich in the aforementioned nutrients, whereas nutrients taken in isolation in the form of supplements won't work to the same extent."
The scientists are now investigating whether sardines influence a person's gut bacteria, which "affects the regulation of many biological process and we need to understand if they have played a part in this protective effect against diabetes 2".
Watch: Most humans are vulnerable to type 2 diabetes