Scientists have found a link between the frequent use of sugary drinks like sodas and fruit juices and cognitive decline. Those who frequently drank sugary beverages had a poorer memory and suffered from brain shrinkage, mostly in the hippocampus which is a vital brain area responsible for memory formation and retrieval.

Credit: Flickr, Alexander Kaiser.

Matthew Pase and colleagues from the department of neurology at Boston University School of Medicine (BUSM) used data from the Framingham Heart Study (FHS) to see how sugary drinks impact cognition. They selected approximately 4,000 participants from the FHS dataset who were 30 years of age or older. All the participants underwent Magnetic Resonance Imaging (MRI) which scanned their brains and had their cognitive health assessed with standard questionnaires. Each participant consumed more than two sugary drinks a day of any type—soda, fruit juice, and other soft drinks.

The researchers also monitored 2,888 patients who were 45 years of age or older for any stroke incidence. Another 1,484 participants aged 60 or older were monitored for dementia across a period of 10 years.

It’s well established that excessive consumption of sugary drinks heightens the risk of developing obesity, heart disease, and type 2 diabetes, but little is known about the potential health effect of sugary drinks on cognition. While it’s not a causal relationship, the Boston researchers found multiple signs of accelerated brain aging, including smaller overall brain volume, poorer episodic memory, and a shrunken hippocampus. The more sugary drinks a participant used on a daily basis, the more pronounced was the correlation.

If you think going diet soda is any better, the findings say otherwise. Drinking one diet soda a day was also associated with smaller brain volume. Those who drank diet soda daily were almost three times as likely to develop stroke and dementia when compared to those who did not.

“Our findings indicate an association between higher sugary beverage intake and brain atrophy, including lower brain volume and poorer memory,” explained Pase,

“These studies are not the be-all and end-all, but it’s strong data and a very strong suggestion,” says Sudha Seshadri, a professor of neurology at Boston University School of Medicine (MED) and a faculty member at BU’s Alzheimer’s Disease Center, who is senior author on both papers. “It looks like there is not very much of an upside to having sugary drinks, and substituting the sugar with artificial sweeteners doesn’t seem to help.”

“Maybe good old-fashioned water is something we need to get used to,” she adds.

For their two studies published in the journals Alzheimer’s & Dementia and Stroke, the researchers were careful to consider age, smoking, diet quality, and other factors into account. They admit, however, they couldn’t completely control for preexisting conditions like diabetes, which may have developed over the course of the study and is a known risk factor for dementia. Diabetics are known to consume more diet soda to control their sugar intake but even so, the magnitude of the findings can’t be wholly explained by these pre-existing conditions. “It was somewhat surprising that diet soda consumption led to these outcomes,” says Pase whose team is the first to find an association between diet soda and dementia. The underlying mechanisms, however, remain somewhat of a mystery. Artificial sweeteners may be to blame as these can alter gut bacteria or alter the brain’s perception of ‘sweet’. More investigations might shed light.