Eating a small portion of mixed nuts each day can help with weight loss, new research has revealed.

Scientists have found a link between eating nuts and higher levels of serotonin, a hormone that is most commonly known for boosting happiness but also decreases appetite and improves heart health.

Researchers from the University of Barcelona found that as little as one ounce of raw and unpeeled walnuts, almonds and hazelnuts a day, can produce positive health effects.

The findings, published in the Journal of Proteome Research, will benefit patients with metabolic syndrome (MetS), a condition that causes excess abdominal fat, high sugar and high blood pressure.

The research team put 22 MetS patients on a nut-enriched diet for 12 weeks and compared them to another group of patients who were given a nut-free diet.

After examining the patients' urine, it was found that those consuming 30 grams of mixed nuts a day had higher serotonin levels.

Lead researcher, Christina Andris-Lacueva, said: "An increased excretion of serotonin metabolites was associated for the first time with nut consumption."

Researchers believe the findings could help patients shed excess weight, decreasing the risk of developing type 2 diabetes and heart disease.

Before you rush out to buy a family bag of mixed nuts in hope of shedding a few pounds, be aware that nuts, while packed with nutrients, are highly calorific so stick to a handful a day.