Diet can reduce your risk of Alzheimer’s. But not the way that headlines claim

    21 March 2016

    Sales of maple syrup are sure to rise after a study at the University of Rhode Island suggested the sugary treat had a neuroprotective effect in mice. Research leader Dr Navindra Seeram advised against drawing too much from these findings, but the story was too good to resist: headlines around the world announced that maple syrup ‘could prevent Alzheimer’s’.

    Indeed, a few days earlier we were told that snacking on blueberries could help fight the disease. All we need now is a study on pancakes and we might have the perfect Alzheimer’s-battling breakfast.

    It is easy to become a cynic, but there is at least a theoretical basis to these claims. This is the contested ‘amyloid hypothesis’. This theory posits that Alzheimer’s is the result of a build-up in the brain of peptides (small protein pieces) called beta amyloids. These beta amyloids are sticky, joining together with other peptides to form plaques inside the tissue of the brain, disrupting and destroying nerve cells.

    The theory itself goes all the way back to 1907, to a certain Dr Alois Alzheimer.

    Since then scientists have explored ways of combating the build-up of amyloid plaques, with varying successes. Berries, broccoli, saffron and red wine have all been trumpeted as a way to stave off Alzheimer’s.

    The apparent power of berries, for instance, resides in an antioxidant called anthocyanin. (Handily for those heading to the supermarket, anthocyanin is also a colour pigment, which provides fruits like cherries, blackcurrants and blueberries with their distinctive hue.) The idea is that anthocyanin helps to combat oxidative stress — the process that produces free radicals in cells — and, as a result, inhibits or slows the accumulation of amyloid beta-plaques.

    High cholesterol, meanwhile, is associated with the accelerated formation of beta-amyloid plaques, leading pharmaceutical companies to promote statins as a potential Alzheimer’s cure. But clinical trials have proved inconclusive.

    Sadly, though, there is still a missing piece in the puzzle — scientists do not yet know if the amyloid plaques are a symptom or a cause. Dr Rob Buckle, director of science programmes at the Medical Research Council, says: ‘There is strong evidence for the involvement of plaque deposits, but whether they are a causative, as opposed to being correlative with disease progression, remains unproven.’

    He adds, somewhat bleakly: ‘There is no certainty about what causes neuro-degeneration.’

    Dr Buckle says many of the headline-grabbing Alzheimer’s research projects are not, in fact, very helpful. ‘Most of these studies are in model systems that don’t represent the disease, or they are being done in a way that is methodologically or statistically unsound,’ says Dr Buckle.

    ‘It may be boring to say, but eating healthily, getting your five-a-day and enjoying regular exercise is the best way to reduce your risk of Alzheimer’s,’ he says.

    Diet, it seems, can reduce our risk of Alzheimer’s after all. But this doesn’t mean the blueberry and maple syrup breakfast. The diet with the best evidence behind it is the Mediterranean diet — that is, a diet high in fruit and vegetables, and low in meat, sugar and animal fat. A systematic review in 2013 showed clear benefits, with improved cognitive function and a reduced risk of Alzheimer’s in nine out of 12 studies.

    Researchers don’t know quite why it works, just that it does. And blueberries and broccoli — and possibly even maple syrup — can all play their part.