The festive season may be over, but there is at least one Christmas treat worth making a habit of eating throughout the year – walnuts.

Scientists have discovered they are the healthiest nuts to eat as they are loaded with antioxidants.

Snacking on as few as seven a day could help ward off disease and lower cholesterol, they claim.

Walnuts contain very high levels of polyphenol, an anti-oxidant which can protect the body from molecules which damage tissue.

Walnuts contained the most polyphenol out of a list of nine commonly eaten types of nuts, tests revealed.

Brazil nuts and pistachios were close behind, and cashews and hazelnuts had slightly lower levels of antioxidants.

Professor Joe Vinson, from the University of Scranton, Pennsylvania, said walnuts inhibit the growth of ‘bad’ cholesterol.

He said: ‘Walnuts rank above Brazil nuts, pistachios, pecans, peanuts, almonds, macadamias, cashews and hazelnuts.

‘Walnuts had the highest free and total polyphenols in both the combined and roasted samples’.

Despite the ‘superfood’ potential of walnuts, peanuts are the favourite with consumers and account for 45 per cent of the nuts bought in Europe.

The antioxidants in peanut butter were considerably lower than in roasted peanuts, the study found.

Dr Vinson said many people were put off by the seemingly high fat content of nuts, but they contained only polyunsaturated and monosaturated fats, rather than artery-clogging saturated fats.

He added: ‘Nuts are high in ?bre, low in saturated fats, high in bene?cial unsaturated fats, and very high in antioxidants.

‘Nuts are a nutritious snack providing both nutrients and bioactive antioxidants which provide significant health bene?ts.’

Advising consumers to keep the portion size small, Dr Vinson said it takes only about seven walnuts a day to get the potential health benefits.

The antioxidants found in raw walnuts were 15 times as powerful as Vitamin E, which can protect the body against damaging natural chemicals.

Roasted cashew nuts contained just double the level found in Vitamin E.

Nuts have long been promoted as a nutritious snack by health professionals.

Pecans contain around a sixth of the recommended daily allowance for zinc, which is vital for the functioning of white blood cells that fight bacteria and viruses, including colds and flu.

A couple of handfuls of shelled pistachios have more potassium than a banana. This can help control blood pressure, as part of a healthy diet, because potassium blunts the effects of salt.

And the brazil nut is the richest source of selenium, a nutrient that helps protect cells.

Higher selenium levels have been linked with a reduced risk of certain cancers such as bladder and prostate.