Scientists at Karolinska Institutet in Sweden and the University of North Carolina at Chapel Hill have thrown further weight behind this theory, with an investigation of cellular behavior in the nervous system of the digestive system revealing possible tell-tale signs at the earliest stages of the disease.

The notion that Parkinson's disease could get its start in the gut has been around for some time, but in recent years we are seeing some compelling research that suggests our bellies may well play an important role in its onset. The disease is characterized by the cell death of neurons that secrete dopamine in the brain, which drives the motor impairments and other common symptoms of the illness.

What causes the demise of these neurons is not known for certain, but a leading hypothesis is that it is caused by aggregations of misfolded proteins known as Lewy bodies. An animal study last year produced the best evidence to date that these toxic protein clumps first form in the gut and move upward to the brain via the vagus nerve.

This new research hints at the role the enteric nervous system, as the regulator of digestive system, could play in these processes. Made up of a hundreds of millions of neurons, the body's largest collection outside the brain, the enteric nervous system can operate independently of the central nervous system and for this reason is sometimes referred to as "the second brain."