Peanut butter sandwiches could be the secret to beating heart disease, says a study. Snacking on peanuts or peanut butter at least five days a week can nearly halve the risk of a heart attack.

The nuts are thought to lower bad cholesterol, help reduce inflammation in the body and boost the health of blood vessels around the heart.

Between 1980 and 2002, researchers at Harvard Medical School analysed the diets of more than 6,000 women who had type 2 diabetes, which increases the risk of heart attack and stroke. All the volunteers completed food questionnaires every two to four years.

When the researchers matched up the results with data on how many went on to suffer heart attacks or strokes, they found those regularly eating peanuts had the greatest protection.

In a report on their findings, published in the Journal of Nutrition, they said the risk was reduced by up to 44 per cent.

‘Consumption of at least five servings a week of one ounce of nuts or one tablespoon of peanut butter was significantly associated with a lower risk of cardiovascular disease,’ they said.

In the UK, poor diet and lifestyle has led to a surge in cases of type 2 diabetes, from 1.5million five years ago to 2.25million now.

Ellen Mason of the British Heart Foundation said: ‘It is beneficial to include nuts in our diets as they are low in the saturated fats that raise our cholesterol.

‘However peanut products can be full of added sugar or salt so check the label first. Also don’t forget that nuts are high in overall calories.

‘Eating more of one food in isolation will not make a dramatic difference to your health if you are inactive and don’t have a balanced diet.’