Could Diet Soda Increase Dementia Risk?
Summary
- The Miller School’s Dr. Hannah Gardener is studying the impact of diet soda consumption on brain health.
- Dr. Gardener investigated 947 NOMAS participants who reported their diet soda habits.
- The study found, for program participants, each additional diet soda per day was linked to a 34% increase in dementia risk.
A new analysis from the long‑running Northern Manhattan Study (NOMAS) suggests that drinking diet soda every day may be linked to a higher risk of developing dementia, particularly among non‑Hispanic white and Black adults. While more research is needed to understand the underlying mechanisms, the findings add to a growing body of evidence connecting artificially sweetened beverages with cardiometabolic and cognitive outcomes.
The study, published in the Journal of Alzheimer’s Disease, was led by investigators at the University of Miami Miller School of Medicine, including:
• Hannah Gardener, Sc.D., an epidemiologist and research associate professor in neurology
• Tatjana Rundek, M.D., professor of neurology, the Evelyn F. McKnight Chair for Learning and Memory in Aging and scientific director at the Evelyn F. McKnight Brain Institute
• Christian Agudelo, M.D., assistant professor of clinical neurology
• Tali Elfassy, Ph.D., research assistant professor in the Katz Family Division of Nephrology and Hypertension
• Arielle Farhi, M.D., a resident in the Department of Physical Medicine and Rehabilitation
“Diet soda is likely not a healthy alternative to regular, sugar-sweetened soda when it comes to protecting brain health,” said Dr. Gardener, senior author of the study and a longstanding NOMAS investigator. “Further, rigorous research is needed to help elucidate whether diet soda is causally associated with dementia risk. The existing evidence suggests that diet soda and regular soda should be consumed minimally for health protection.”
The research team collaborated with researchers at Columbia University.
Diet and Cognitive Aging
NOMAS is a population‑based cohort designed to identify risk factors for stroke and cognitive decline among residents of Northern Manhattan, a diverse urban community with high representation of Hispanic, non‑Hispanic Black and non‑Hispanic white adults. Participants were originally enrolled between 1993 and 2001. A subset underwent brain MRI imaging and cognitive testing that enabled investigators to evaluate long‑term cognitive trajectories.
For this analysis, researchers examined 947 adults who had:
• Completed baseline dietary assessments, including soda consumption
• Undergone repeated neuropsychological testing
• No dementia at the time of their first cognitive evaluation
Participants were, on average, 64 years old at baseline. More than 20% developed dementia over years of follow‑up.
How Soda Intake Was Measured
Diet and regular soda intake were captured using a detailed food frequency questionnaire. Participants reported how often they consumed diet or sugar‑sweetened soft drinks, ranging from “never” to “six or more per day.” Researchers evaluated soda intake categorically (more than one soda per day versus less than one soda per day) and continuously (average number of sodas per week).
Clinicians should talk to their patients about the foods and beverages they consume and advocate for dietary changes that may promote brain health starting early in life, decades before people start exhibiting cognitive decline.
Dr. Hannah Gardener
Importantly, only a small percentage reported high soda intake. Just more than 2% drank more than one diet soda per day. Just shy of 5% drank more than one regular soda per day. These patterns mirror national data showing higher use of diet soda among middle‑aged adults and individuals managing chronic conditions such as diabetes or obesity.
Key Findings: Diet Soda Stands Out
After adjusting for demographics, lifestyle behaviors and vascular risk factors, the research team observed a consistent association between diet soda consumption and dementia risk:
• Each additional diet soda per day was linked to a 34% increase in dementia risk.
• Participants who drank more than one diet soda daily had approximately four times the risk of developing dementia compared to those who drank one or fewer daily.
Notably, regular soda consumption was not associated with dementia in any multivariable model.
Exploratory analyses suggested that the elevated dementia risk associated with diet soda was strongest in non‑Hispanic white and Black participants.
What Might Explain the Link?
The biological mechanisms connecting diet soda to dementia are not yet clear. Diet soda has been previously associated with:
• Increased risk of stroke, myocardial infarction and diabetes
• Greater abdominal adiposity and poorer metabolic profiles
• Altered gut hormone signaling, including effects on GLP‑1
Vascular damage plays a major role in the development of dementia, so it is plausible that metabolic and vascular effects of diet soda indirectly influence cognitive decline.
But reverse causation is also possible. Individuals with obesity or diabetes may switch to diet soda to reduce sugar intake. Supporting this, 41% of high diet soda consumers in the study had diabetes, compared with 18% of the rest of the cohort.
When researchers repeated the analysis excluding participants with obesity or diabetes, the association between diet soda and dementia disappeared. This raises questions about whether diet soda is a driver or a marker of underlying health risks.
Implications for Patient Care
Although the findings do not prove that diet soda causes dementia, they reinforce the importance of discussing beverage choices with patients, especially those at high risk for metabolic or cardiovascular disease. Clinicians may consider:
• Encouraging reduced reliance on artificially sweetened beverages
• Promoting water and unsweetened alternatives, such as coffee and tea
• Monitoring metabolic risk factors closely in heavy diet soda consumers
“Clinicians should talk to their patients about the foods and beverages they consume and advocate for dietary changes that may promote brain health starting early in life, decades before people start exhibiting cognitive decline,” said Dr. Gardener. “The existing data have consistently shown that adherence to a Mediterranean style diet, with beverages including water, tea, and coffee, can help reduce the risk of cognitive impairment and dementia, as well as so many other health conditions, including stroke and myocardial infarction.”
The study also highlights the need for culturally tailored dietary guidance, as risk patterns may vary among racial and ethnic groups.
Next Steps in Research
As research in this area continues, the authors emphasize the need for:
- Larger, diverse cohort studies with lifelong dietary tracking
- Better differentiation of artificial sweetener types and formulations
- Mechanistic research exploring vascular, metabolic and neurobiological pathways
- Investigation into the interactions between beverage choices and social or behavioral factors
As the landscape of artificial sweeteners continues to evolve, understanding their long‑term effects on brain health will be essential.
Tags: Alzheimer's disease, brain health, cognitive decline, dementia, Dr. Christian Agudelo, Dr. Hannah Gardener, Dr. Tali Elfassy, Dr. Tatjana Rundek, Evelyn F. McKnight Brain Institute, neurology, neuroscience, Newsroom, Northern Manhattan Study