Both sugary, diet drinks correlated with accelerated brain aging
Boston University
Americans love sugar. Together we consumed nearly 11 million
metric tons of it in 2016, according to the US Department of Agriculture, much
of it in the form of sugar-sweetened beverages like sports drinks and soda.
Now, new research suggests that excess sugar -- especially the
fructose in sugary drinks -- might damage your brain. Researchers using data
from the Framingham Heart Study (FHS) found that people who drink sugary
beverages frequently are more likely to have poorer memory, smaller overall
brain volume, and a significantly smaller hippocampus -- an area of the brain
important for learning and memory.
But before you chuck your sweet tea and reach for a diet soda,
there's more: a follow-up study found that people who drank diet soda daily
were almost three times as likely to develop stroke and dementia when compared
to those who did not.
Researchers are quick to point out that these findings, which appear separately in the journals Alzheimer's & Dementia and Stroke, demonstrate correlation but not cause-and-effect.
While researchers caution against over-consuming either diet soda or sugary drinks, more research is needed to determine how -- or if -- these drinks actually damage the brain, and how much damage may be caused by underlying vascular disease or diabetes.
"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."
"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.
Matthew Pase, a fellow in the MED neurology department and an
investigator at the FHS who is corresponding author on both papers, says that
excess sugar has long been associated with cardiovascular and metabolic
diseases like obesity, heart disease, and type 2 diabetes, but little is known
about its long-term effects on the human brain. He chose to study sugary drinks
as a way of examining overall sugar consumption. "It's difficult to
measure overall sugar intake in the diet," he says, "so we used
sugary beverages as a proxy."
For the first study, published in Alzheimer's &
Dementia on March 5, 2017, researchers examined data, including
magnetic resonance imaging (MRI) scans and cognitive testing results, from
about 4,000 people enrolled in the Framingham Heart Study's Offspring and
Third-Generation cohorts. (These are the children and grandchildren of the
original FHS volunteers enrolled in 1948.)
The researchers looked at people who consumed more than two sugary drinks a day of any type -- soda, fruit juice, and other soft drinks -- or more than three per week of soda alone. Among that "high intake" group, they found multiple signs of accelerated brain aging, including smaller overall brain volume, poorer episodic memory, and a shrunken hippocampus, all risk factors for early-stage Alzheimer's disease.
Researchers also found that higher intake of diet soda -- at least one per day -- was associated with smaller brain volume.
The researchers looked at people who consumed more than two sugary drinks a day of any type -- soda, fruit juice, and other soft drinks -- or more than three per week of soda alone. Among that "high intake" group, they found multiple signs of accelerated brain aging, including smaller overall brain volume, poorer episodic memory, and a shrunken hippocampus, all risk factors for early-stage Alzheimer's disease.
Researchers also found that higher intake of diet soda -- at least one per day -- was associated with smaller brain volume.
In the second study, published in Stroke on
April 20, 2017, the researchers, using data only from the older Offspring
cohort, looked specifically at whether participants had suffered a stroke or
been diagnosed with dementia due to Alzheimer's disease.
After measuring volunteers' beverage intake at three points over seven years, the researchers then monitored the volunteers for 10 years, looking for evidence of stroke in 2,888 people over age 45, and dementia in 1,484 participants over age 60.
Here they found, surprisingly, no correlation between sugary beverage intake and stroke or dementia. However, they found that people who drank at least one diet soda per day were almost three times as likely to develop stroke and dementia.
After measuring volunteers' beverage intake at three points over seven years, the researchers then monitored the volunteers for 10 years, looking for evidence of stroke in 2,888 people over age 45, and dementia in 1,484 participants over age 60.
Here they found, surprisingly, no correlation between sugary beverage intake and stroke or dementia. However, they found that people who drank at least one diet soda per day were almost three times as likely to develop stroke and dementia.
Although the researchers took age, smoking, diet quality, and
other factors into account, they could not 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, as a group, drink more diet soda on average, as a way to limit their sugar consumption, and some of the correlation between diet soda intake and dementia may be due to diabetes, as well as other vascular risk factors. However, such preexisting conditions cannot wholly explain the new findings.
Diabetics, as a group, drink more diet soda on average, as a way to limit their sugar consumption, and some of the correlation between diet soda intake and dementia may be due to diabetes, as well as other vascular risk factors. However, such preexisting conditions cannot wholly explain the new findings.
"It was somewhat surprising that diet soda consumption led
to these outcomes," says Pase, noting that while prior studies have linked
diet soda intake to stroke risk, the link with dementia was not previously
known.
He adds that the studies did not differentiate between types of artificial sweeteners and did not account for other possible sources of artificial sweeteners. He says that scientists have put forth various hypotheses about how artificial sweeteners may cause harm, from transforming gut bacteria to altering the brain's perception of "sweet," but "we need more work to figure out the underlying mechanisms."
He adds that the studies did not differentiate between types of artificial sweeteners and did not account for other possible sources of artificial sweeteners. He says that scientists have put forth various hypotheses about how artificial sweeteners may cause harm, from transforming gut bacteria to altering the brain's perception of "sweet," but "we need more work to figure out the underlying mechanisms."