Food for thought: Eat your way to dementia

SUZANNE DE LA MONTE's rats were disoriented and confused. Navigating their way around a circular water maze - a common memory test for rodents - they quickly forgot where they were, and couldn't figure out how to locate the hidden, submerged safety platform. Instead, they splashed around aimlessly. "They were demented. They couldn't learn or remember," says de la Monte, a neuropathologist at Brown University in Providence, Rhode Island.

A closer look at her rats' brains uncovered devastating damage. Areas associated with memory were studded with bright pink plaques, like rocks in a climbing wall, while many neurons, full to bursting point with a toxic protein, were collapsing and crumbling. As they disintegrated, they lost their shape and their connections with other neurons, teetering on the brink of death.

Such changes are the hallmarks of Alzheimer's disease, and yet they arose in surprising circumstances. De la Monte had interfered with the way the rats' brains respond to insulin. The hormone is most famous for controlling blood sugar levels, but it also plays a key role in brain signalling. When de la Monte disrupted its path to the rats' neurons, the result was dementia.

Poor sensitivity to insulin is typically associated with type 2 diabetes, in which liver, fat and muscle cells fail to respond to the hormone. But results such as de la Monte's have led some researchers to wonder whether Alzheimer's may sometimes be another version of diabetes - one that hits the brain. Some have even renamed it "type 3 diabetes".

But certain dishes may offer some protection against these effects. Rats consuming high-fructose corn syrup water alongside omega-3-fatty acids from flaxseed oil seemed to escape the cognitive problems the other group encountered (Journal of Physiology, vol 590, p 2485). Omega-3 acids are also found in oily fish.

There is also some tentative evidence that certain compounds called flavonoids, found in tea, red wine and dark chocolate, can reduce the risk of dementia. All of which may explain why the Mediterranean diet is associated with less cognitive decline, dementia and Alzheimer's disease. This diet is known to be rich in fish and vegetable oils, non-starchy vegetables, low glycaemic fruits, less added sugar and a moderate helping of wine (Current Alzheimer Research, vol 8, p 520).