Swedish research has found a link between fast food and Alzheimer's disease.
The research by scientists at the Karolinska Institutet has revealed that mice fed a diet of junk food for a nine month period developed the abnormal brain tangles which are seen in the preliminary stages of Alzheimer's disease - they say a diet rich in fat, sugar and cholesterol could increase the risk of the most common type of dementia.
According to Susanne Akterin, a postgraduate researcher at the Institute's Alzheimer's Disease Research Center, who led the study, the diet caused a chemical change in the brains of the mice similar to that found in the Alzheimer brain.
Ms Akterin says this has led to the suspicion that a high intake of fat and cholesterol in combination with genetic factors can adversely affect several brain substances, which contribute the development of Alzheimer's.
Alzheimer's disease is the most common form of dementia among older people and is incurable - it affects the parts of the brain involved with thought, memory and language.
Alzheimer's disease is difficult to treat and new drugs focus on removing clumps of beta amyloid protein that forms plaques in the brain but researchers are also examining ways to deal with the toxic tangles caused by an abnormal build-up of the protein tau.
Akterin's research focused on a gene variant called apolipoprotein E (apoE4) found in 15 to 20% of people which is a known risk factor for Alzheimer's - apoE4 is also involved in the transport of cholesterol.
For the study mice were used which were genetically engineered to mimic the effect of the variant gene in humans which were then fed a diet rich in fat, sugar and cholesterol for nine months - meals with a similar nutritional content of fast food.