Sweet Drinks: Bad for Your Brain?
Both sugary and artificially-sweetened drinks have been called into question for possible links with Alzheimer's disease and stroke risk.
Could a sugary-drink habit - or the diet beverages you may consume instead - harm your brain? One recent study showed that regularly drinking sugary beverages, like soda and fruit drinks, was associated with signs of brain aging and declining memory. A second study showed that frequently drinking artificially-sweetened (diet) beverages was associated with greater risks of stroke and dementia (impaired memory and thinking skills). So, what does this mean for how you choose to quench your thirst?
Paul Jacques, DSc, a coauthor of both studies and the director of Tufts' HNRCA Nutritional Epidemiology Program, points out that the studies were observational, so they can't prove cause and effect. "However, there's a lot of evidence that sugar-sweetened beverages are associated with metabolic disease (like heart disease, abdominal obesity and fatty liver)," he says. "So regardless of how they might affect the brain, they’re not healthy and their consumption should be limited or avoided."
How to approach diet drinks is less clear. "There's some previous evidence that higher consumption of artificially-sweetened beverages is linked to development of metabolic disease, such as type 2 diabetes," Jacques says. "However, a key challenge in interpreting most studies on artificially-sweetened beverages is that we don’t know whether adverse health effects associated with their use are due to the sweeteners themselves or to underlying health issues that may have prompted people to choose them. Although the evidence of harm is limited, we should be cautious of consuming artificially-sweetened drinks too frequently."
The first of the two studies, published in Alzheimer's & Dementia, involved about 4,000 adults averaging 54 years of age from the Framingham Heart Study. It showed that compared to infrequent consumption (less than one glass, bottle or can a day) of sugary drinks, consuming one or two sugary beverages a day was associated with having a smaller brain volume, which is a risk factor for Alzheimer's-type dementia. Additionally, testing showed higher intake of all sugary beverages was associated with poorer episodic memory, which is the ability to recall events in your life. It's a strong predictor of Alzheimer's disease risk.
The sugary drinks included regular sodas and fruit beverages (100% fruit juice or sugar-sweetened fruit drinks). The findings were true whether soda and fruit beverages were grouped or looked at separately.
"Compared to not drinking sugary beverages, consuming one or two sugary beverages (all types combined) a day was associated with memory scores equal to six years of brain aging," says Matthew P. Pase, PhD, the lead author of both studies at Boston University School of Medicine. "And, consuming more than two sugary beverages a day was associated with memory scores equal to 11 years of brain aging."
It may seem surprising that higher intake of fruit-based beverages was associated with Alzheimer's-like brain changes and memory loss. It's unknown what portion of those drinks had added sugar. But, a high intake of sugar in liquid from any source may be problematic.
"Our bodies are set up to metabolize sugar [transform it into energy]," Jacques says. "However, the large amount of sugar people sometimes consume can overwhelm our ability to appropriately metabolize it, potentially contributing to health issues." Since even 100% juice has little fiber and can be consumed very quickly, limit it to a ½- to 1-cup serving per day.
The Alzheimer's & Dementia study showed that diet beverage intake was associated with smaller brain volume. The second study, published in Stroke, adds to the concern. This research involved Framingham Heart Study participants, too, but focused on older members of the group. Those who reported consuming at least one diet drink daily had about three times the risk of developing a stroke (especially the ischemic kind, caused by blocked blood vessels) or dementia over 10 years of follow-up compared to not drinking diet beverages.
Notably, the number of people who developed stroke or dementia in this study was relatively small. About 3% had a stroke and 5% developed dementia, primarily Alzheimer's disease.
No association was found between sugary drinks and dementia or stroke risk in this study (which adjusted for high blood pressure and other factors). But, the people more commonly consumed diet drinks.
"This research calls into question whether diet drinks are really a better alternative to sugary beverages," Pase says. "We need to do more research to understand the effects of artificially-sweetened drinks on different aspects of health, including the brain, and in more diverse populations." His advice: drink water.
Lastly, added sugars in foods aren't off the hook. Added sugar intake from foods just isn’t as easy to measure as from drinks. Limit added sugar from any source since it’s already linked with health risks.
To learn more: Alzheimer’s & Dementia, March 2017 -
To learn more: Stroke, May 2017 -