Sugar may up Alzheimer's

Eating too much sugar could be bad for your brain as well as your teeth, the results of a new study with mice suggests.

Mice bred to develop an Alzheimer's-like disease that were given sugar-sweetened water had a greater decline in learning skills and memory compared with mice that drank pure water, Dr Dongfeng Cao and colleagues from the University of Alabama at Birmingham found. What's more, the animals that consumed sugar had a greater degree of Alzheimer's-like damage to their brains.

"Our findings are of tremendous importance given that the consumption of sugar-sweetened beverages has increased dramatically over the past decades and will most likely remain high in modern societies," Cao and his team said.

Type 2 diabetes, Alzheimer's lined
Several recent studies have found that people with type 2 diabetes are at increased risk of developing Alzheimer's disease, the researchers point out in the Journal of Biological Chemistry. But it has not been clear how diabetes could influence Alzheimer's disease development.

To look at the effects of a high-sugar diet, the researchers compared mice given water containing 10 percent sucrose with mice that drank plain water. Sucrose is common table sugar.

After 25 weeks, the animals given sweetened water weighed 17 percent more than the control mice. While the sucrose-drinking mice ate less food than those given plain water, the amount of sucrose they consumed pushed their calorie consumption 15 percent higher; they obtained 43 percent of their total calories from sucrose. These mice also developed early signs of diabetes and had excessive amounts of fat in their blood.

Learning, memory impaired
In behavioural tests, the mice given sweetened water also showed significant impairments in learning and memory compared to those given pure water.

The brains of the sucrose-fed animals had three times the amount of the Alzheimer's-associated protein amyloid-beta, and roughly 2.5-times as much apolipoprotein-E, a protein that, in mice, promotes the formation of the "plaques" and "tangles" in brain tissue that are the hallmark of the disease.

The amount of sucrose the mice consumed was equivalent to a human drinking five cans of sugar-sweetened soda a day, Cao and colleagues noted. But it's possible people wouldn't have to consume this much sucrose for similar brain changes to develop, they add, given that the soda was the only sucrose source in the animals' diet and that mice have a metabolic rate that is 7-times higher than humans'.

Based on these findings, the researchers conclude: "Controlling the consumption of sugar-sweetened beverages may be an effective way to curtail the risk of developing Alzheimer's disease." - (Reuters Health)

SOURCE: Journal of Biological Chemistry

Read more:
Brain a clue to false memories
Alzheimer's Centre

December 2007

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