The high protein diet was popular in the 1990s as a diet approach, and was commercialised in the form of the Atkins Diet and others. The approach caused great concern among dieticians who advise that a healthy diet should include all macronutrients. The Atkins approach has since been amended to include carbohydrates.
For a new study published in the open-access journal Molecular Neurodegeneration, a research team from the UK, US and Canada set out to investigate the potential dietary triggers to the formation of amyloid plaques that are linked to Alzheimer’s.
They noted that previous epidemiological evidence has suggested that low-calorie, low-fat diets with plenty of fruit, vegetables and fish could delay onset or progression of the degenerative disease.
The finding that the high protein diet led to lighter brains was a surprise result, and one that merits further investigation in both mice and humans for a potential link to Alzheimer’s incidence or progression.
The research team, led by neurologist Sam Gandy of The Mount Sinai School of Medicine in New York, worked with mice that had been engineered to express a form of the amyloid precursor protein, which leads to plaque formation.
They fed four different diets to different groups of mice, from the age of 4 weeks: A regular diet of commercial chow; a chow with 60 per cent of calories from fat and 30 per cent from protein; a chow with 60 per cent protein and 30 per cent carb; and a chow with 60 per cent carbs, 30 per cent protein and 10 per cent fat.
At 18 weeks the mice were sacrificed and their brain and body weights taken. Their brains were analysed for plaque build up and the structure of hippocampal regions that have a role to play in the memory defect of Alzheimer’s.
“Unexpectedly, brains of mice fed a high protein/low carbohydrate diet [protein 60: carbs 30] were 5 per cent lower in weight than brains from all other mice,” they wrote. In addition, regions of their hypocampus were underdeveloped.
The team said it is unclear whether the loss of brain mass is associated with plaque build up, and this needs to be tested on non-transgenic mice.
However they did put forward a tentative theory, that the high protein diet could leave neurons more vulnerable to plaque.
“Given the previously reported association of high protein diet with aging-related neurotoxicity, one wonders whether particular diets, if ingested at particular ages, might increase susceptibility to incidence or progression of Alzheimer’s disease," said Gandy.
In order to find out if a high protein diet has a similar effect on humans, prospective randomised double blind clinical diet trials would be needed.
"This would be a challenging undertaking but potentially worthwhile if there is a real chance that the ravages of Alzheimer’s disease might be slowed or avoided through healthy eating," Gandy said. "Such trials will be required if scientists are ever to make specific recommendations about dietary risks for Alzheimer’s disease."
Molecular Degeneration (in press)
“Dietary composition modulates brain mass and amyloid beta levels in a mouse model of aggressive Alzheimer’s amyloid pathology”
Authors: Steve Pedrini, Carlos Thomas, Hannah Brautigam, James Schmeidler, Lap Ho, Paul Fraser, David Westaway, Peter Hyslop, Ralph Martins, Joseph Buxbaum, Giulio Pasinetti, Dara Dickstein, Patrick Hof, Michelle Ehrlich and Sam Gandy