Could a Mediterranean diet prevent Alzheimer’s disease?

With dementia now the biggest single cause of death in the UK, Britons are more conscious than ever of understanding how to reduce the risk of developing Alzheimer’s disease in later life.

Although dementia has a genetic component, recent studies support the theory that lifestyle plays a greater role in determining risk. For instance, Japan and Nigeria are among the nations with a relatively low prevalence of dementia, but Japanese-Americans and African-Americans develop dementia at a similar rate to other Americans, write Michael Gregar and Gene Stone in How Not To Die.

The so-called “Mediterranean diet” is frequently touted for its health benefits, linked to a lower risk of everything from strokes to heart attacks - and there is “some evidence” that it could also reduce the risk developing some forms of dementia, says the Alzheimer’s Society. This includes Alzheimer’s disease, the most common form of dementia.

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Are dementia rates lower in Mediterranean countries?

At first glance, the World Health Organisation’s dementia death per capita index appears to do little to support the Mediterranean diet theory: Spain comes in at 20, with Italy - often viewed as emblematic of the Mediterranean diet - at 21.

However, in an increasingly globalised world, inhabitants of Mediterranean countries do not necessarily follow the traditional diet of centuries past. Diets in highly-developed nations, high in red meat, sugar and processed foods, are connected with higher rates of dementia compared to less-developed nations.

What foods are connected with low dementia rates?

To see the true benefits of a Mediterranean-style diet, it is necessary to look at specific communities where this lifestyle still prevails.

Some of the lowest rates of dementia in the world are found in “the Okinawa islands of Japan… the Nicoya area of Costa Rica, the PACA region of southeastern France or the adjacent Liguria district of northwest Italy - with other pockets of exceptional health located in Greece, Spain, Central and South America”, says Awakening from Alzheimer’s.

At first glance, these low-dementia regions may appear gastronomically diverse, but their diets share crucial similarities.

These include a low consumption of dairy and red meat, with diets dominated by pulses, grains, green vegetables and herbs. Fats are derived mostly from monounsaturated sources such as fish and olive oil, rather than the saturated and trans fats found in processed meat, lard, biscuits or pastry.

These low-dementia regions also consume food known to enrich gut bacteria, be it red wine, yoghurt, soy sauce or pickled vegetables.

Why is the Mediterranean-style diet linked to lower dementia risk?

The prestigious US Mayo Clinic says that the exact nature of the link between a Mediterranean-style diet and a lower dementia risk is unclear.

Some scientists believe that the healthy cholesterol and blood sugar levels associated with a Mediterranean-style diet may improve “overall blood vessel health, which may in turn reduce the risk of MCI or Alzheimer’s disease”.

“Another theory suggests that following a Mediterranean diet may help prevent brain tissue loss associated with Alzheimer’s.”