Eating nuts, particularly walnuts, may help to prolong your life, a new study indicates.

Spanish scientists looked at over 7,000 people aged between 55 and 90. Half were told to consume a Mediterranean diet, while the other half followed a low-fat diet.

The Mediterranean diet involves a high intake of olive oil, fruit, vegetables, nuts, seeds, fish and starchy foods such as red potatoes and pasta. Dairy products, poultry and wine are consumed in low to moderate amounts, while red meat is rarely eaten.

The study found that people who consumed a high amount of nuts tended to have a lower body mass index (BMI) and a smaller waist measurement.

They were also less likely to have type 2 diabetes or to be taking medicine for high blood pressure.

Nut eaters also tended to be more physically active and were less likely to smoke compared to those who never or rarely consumed nuts.

Overall, those who ate large amounts of nuts had a 39% lower risk of death than those who ate low amounts or none. For people who ate walnuts, this risk was even lower - 45%.

Meanwhile, people who consumed more than three servings of nuts per week had a 55% reduced risk of dying from heart disease and a 40% reduced risk of dying from cancer. One serving was considered around 28g. This was irrespective of the type of nuts eaten.

"Quite how nuts are able to prevent premature mortality is not entirely clear, nor why walnut should be better for you than other nuts. Walnuts have particularly high content of alpha-linoleic acid and phytochemicals, especially in their ‘skin' both of which, along with fibre and minerals such as calcium, magnesium and potassium, may contribute to their healthy effect," the scientists commented.

Details of these findings are published in the journal, BMC Medicine.