Sugar & Alzheimer's: Are They Linked?

In Small Study, Sugar-Fed Mice Showed More Evidence of Plaques in Brain

By Salynn Boyles
WebMD Medical News

Reviewed By Louise Chang, MD

Dec. 7 2007 -- Drinking too many sugary sodas may increase a person's risk for developing Alzheimer's disease late in life, new research suggests.

The small study was conducted in mice, not humans, and it falls far short of proving a link between the consumption of sugary beverages and Alzheimer's.

But study co-author Ling Li, DVM, PhD, of the University of Alabama at Birmingham says the findings add to the evidence implicating poor diet as a risk factor for Alzheimer's risk.

The mice were fed either water or sugar water equivalent to five cans of regular soda a day for a human.

The brains of the mice fed sugar water had more evidence of Alzheimer's disease than mice fed regular water.

"We are not saying that people who drink five cans of soda a day will get Alzheimer's," Li tells WebMD.  "But there are many good reasons to limit sugar and sugary soft drinks, and this may be one more."

Diet and Alzheimer's

The study included specially bred mice genetically predisposed to develop symptoms similar to Alzheimer's in adulthood.

Over 25 weeks, eight of the mice received a regular diet, consisting of feed and regular water. Seven other mice ate the same feed, but they drank a water/sugar solution, and 43% of their overall caloric intake was from sugar.

The sugar-fed mice gained about 17% more weight over the course of the study. They also had higher cholesterol and were more likely to develop insulin resistance, a hallmark of diabetes.

These mice also performed worse than non-sugar-fed mice on some tests designed to measure learning and memory retention.

The brains of the sugar-fed mice had about twice as many plaque deposits as the mice fed regular water.

The study is published in the latest issue of the journal Biological Chemistry.

Study Proves Little, Critic Says

The researchers say the study provides compelling early evidence of a link between high sugar consumption and Alzheimer's disease.

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

But a spokeswoman for American Beverage Association (ABA) says the study was far too small to prove anything.

The study included seven sugar-fed mice and eight control mice.

"Lab studies usually involve hundreds of mice, if not thousands," ABA senior vice president for science policy Maureen Storey, PhD, tells WebMD.

"This was a very small study with specially bred mice, and the differences between the control and the treatment mice were not statistically significant," she says, meaning the differences could have been due to chance.

"Alzheimer's disease is a very scary condition. It scares me as a baby boomer. It scares my parents. As scientists we have to be very sensitive to this," she says.

While Storey says the study failed to show "any convincing evidence" of a link between sugary drinks and Alzheimer's disease, she agrees that people should limit their consumption of these drinks.

"The average person doesn't drink five cans of soda a day," she says. "The average person is drinking maybe one can."

SOURCES: Cao, D., Journal of Biological Chemistry, December 2007; online edition. Ling Li, DVM, PhD, University of Alabama at Birmingham. Maureen L. Storey, PhD, senior vice president for science policy, American Beverage Association.

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