Researchers at Veterans Affairs Puget Sound Health Care System followed 20 healthy older people and 29 people with amnestic mild cognitive impairment (aMCI) on different diets for four weeks. People with aMCI experience difficulties with their memory, although not to an extent that interferes with everyday life. About half of people with aMCI will develop dementia, usually Alzheimer’s, within five years of diagnosis.
In a randomised controlled trial, 24 participants followed diets that were high in saturated fat and fast-acting carbohydrates (High) – foods that are already associated with an increased risk of type 2 diabetes. The other 25 people followed diets that had slower acting carbohydrates and were low in saturated fats (Low).
Cognitive tests were carried out before and after the trial, and the researchers measured levels of amyloid and tau – two hallmark proteins associated with Alzheimer’s – in the participants’ cerebrospinal fluid (CSF) before and after the trial.
They found levels of amyloid and tau in CSF were reduced in healthy people who followed the Low diet, while amounts of the proteins increased in healthy people on the High diet. Amyloid and tau levels were raised in people with aMCI on the Low diet, and unchanged in people with aMCI on the High diet.
The researchers believe their results, which are published in Archives of Neurology, suggest that changes to our diet could alter our risk of developing Alzheimer’s, but that dietary interventions are less effective after cognitive decline has begun.
Dr Simon Ridley, Head of Research at Alzheimer’s Research UK, said:
“This is a very small study, but it does add to growing evidence for a link between diet and the early development of Alzheimer’s disease. However, trials will need to be expanded substantially, both in terms of participants and time, before we can fully understand how our diets might affect our Alzheimer’s risk.
“Research is the only answer to dementia, yet research is desperately underfunded. If we are to find a way to prevent the onset of dementia, we must invest in research now.”
Alzheimer’s Research UK