CLAIM: An Instagram post claims drinking one Diet Coke daily makes people nearly 3x more likely to develop dementia, citing a 2017 study. It notes possible links via gut bacteria, insulin response, and eating habits, while acknowledging the studies show association, not proof of direct causation, and that other lifestyle factors may contribute. 

FACTS: Scientific evidence on diet soda and dementia remains mixed and inconclusive. Some research has found associations between artificially sweetened beverage consumption and increased dementia risk, while other analyses, particularly larger ones accounting for underlying health conditions like obesity and diabetes, have found no significant link. Experts caution that existing research shows correlation, not causation, and that lifestyle and metabolic factors likely play a bigger role than any single beverage. 

An Instagram account, gopurehealth, has uploaded a post claiming that people who drink one Diet Coke a day are nearly three times more likely to develop dementia.

The caption of the post says that people who drink Diet Coke are often told it is a healthier choice because it contains no sugar and no calories. However, it notes, some studies have found associations between frequent consumption of artificially sweetened beverages and a higher risk of cognitive decline, stroke and dementia.

While the graphic of the post makes the claim outright, the caption is more measured, noting that studies show a link, not proof, that Diet Coke directly causes dementia.

The Instagram account has a following of over 3.77 lakh, and the post reaches a massive audience, garnering almost 10,000 likes and 370 comments, and being reposted over 200 times.

“Artificial sweeteners may affect gut bacteria, insulin responses, and eating habits in ways researchers are still trying to understand,” the caption states, adding, “Other factors such as obesity, diabetes, cardiovascular disease, smoking, and overall diet may also contribute to the increased risks seen in some studies.”

The post also mentions that current evidence does not prove that having an occasional diet soda will damage one’s brain. “The greater concern appears to be long term, frequent consumption as part of an unhealthy lifestyle,” it says.

It further suggests that if one enjoys Diet Coke, moderation is key: water should remain one’s primary beverage, while unsweetened tea, coffee and sparkling water can be good alternatives. The post ends with a disclaimer urging readers to consult a qualified healthcare professional for personalised advice.

What are the studies saying?

A study published in the Journal of Prevention of Alzheimer’s Disease in 2021 examined the link between sugar in beverages and dementia, Alzheimer’s disease, and stroke, using data from the long-running US Framingham Heart Study.

The prospective cohort study assessed participants’ beverage sugar intake and divided them into three groups: no consumption, moderate consumption, and high consumption. Researchers then tracked incident dementia and stroke cases over an average follow-up period of nearly 19 years. The study noted that “sugar in beverage was assessed between 1991 and 1995 (5th exam).”

After accounting for multiple variables, the study found that participants with the highest sugar-beverage intake had a higher risk of all-cause dementia, Alzheimer’s dementia, and stroke compared to those with no intake, with the same pattern holding among participants with medium-level consumption.

“Higher consumption of sugar in beverage was associated with an increased risk of all dementia, AD dementia and stroke,”  it concluded. 

A second study, published in the Journal of Alzheimer’s Disease in 2025 and based on the Northern Manhattan Study, examined the association between regular and diet soda consumption and dementia risk. 

The longitudinal, population-based study followed 947 dementia-free participants with a mean baseline age of 64 years, assessing soda consumption through a food frequency questionnaire. Dementia was adjudicated during follow-up using neuropsychological and functional assessments, with researchers adjusting for demographic and vascular risk factors.

Of the participants tracked, 20% developed dementia during the follow-up period. Diet soda consumption was associated with increased dementia risk, with those consuming more than one diet soda daily showing higher risk than those consuming less. 

However, the study noted that “the association was not apparent after excluding those with obesity or diabetes, highlighting a potential for reverse causation.” No significant association was found between regular soda consumption and dementia, though a non-statistically significant trend was observed.

What are experts saying?

Dr Lokesh B, senior consultant of neurology at Aster CMI Hospital, Bangalore, urged caution against overinterpreting relative-risk figures drawn from a single 2017 study.

Addressing the “nearly 3x” statistic, he said, “The 2017 study reported an association, not proof that drinking one Diet Coke daily causes dementia.” He pointed to newer evidence complicating the picture, noting, “A 2025 analysis of six prospective US cohorts involving 10,974 older adults found no significant association between artificially sweetened beverage consumption and dementia.”

People with existing metabolic issues may be more inclined to opt for diet drinks over sugary ones in the first place, he explained, which can confound the findings of such studies. He added that the 2025 multicohort analysis accounted for factors such as BMI, diabetes, hypertension, physical activity and heart disease, and still found no significant link.

The theory that sweeteners affect gut bacteria and insulin response, he said, remains a plausible area of research rather than a proven explanation for dementia.

Regarding patient advice, he stated firmly, “I would not tell a patient that drinking one diet soda every day has been proven to cause dementia.”

 “Patients should not be frightened by social-media claims suggesting that a single beverage directly causes dementia,” Dr Lokesh B said.

Also read: FACT CHECK: Does Diet Coke cause cancer?