"The Atkins diet is at the centre of fresh controversy after scientists said it could cause depression and mood swings. Medical experts have found that the diet blocks the brain's ability to produce chemicals that keep us happy.

"Nutritionists have called for people to abandon the diet, claiming they could be risking their mental health as well as physical well-being. "The key to the research is serotonin. This is the chemical released in the brain that keeps us relaxed and positive.

"The team, led by Dr Judith Wurtman at MIT - one of America's top research universities - discovered that high levels of carbohydrates and low levels of proteins are the key to producing enough serotonin to regulate mood. But this is the opposite of the Atkins diet ideal. "According to Dr Wurtman, lowcarb diets can lead to grumpiness, irritability and even depression. She added that the problem was magnified in women, who have naturally lower levels of serotonin in the brain.

"Dr Wurtman said: 'Serotonin is involved in keeping our moods stable, making us calm and serene and allowing us to focus and concentrate. When you take away the carbohydrates, it's like taking away water from someone trekking through the desert."