Diet soda is getting more bad publicity. PepsiCo said this week that its latest quarter was boosted by “guilt-free” products such as diet soda and bottled water, as consumers move away from sugary drinks, but more research is casting a pall over artificially-sweetened beverages too.

Artificially sweetened beverages may be linked to an increased risk of stroke and dementia, according to a recent study by the American Heart Association’s peer-reviewed journal Stroke. The researchers looked at 2,888 people over the age of 45 (with a median age of 62) for stroke risks and 1,484 people over the age of 60 (with a median age of 69) for risk of dementia. After adjustments were made for age, sex, education, caloric intake, diet, exercise, and smoking, they found that diet soda drinks “were associated with an increased risk of ischemic stroke, all-cause dementia, and Alzheimer’s disease dementia.” (The study cites correlation rather than causation.)

Diet soda sales have tumbled as consumers, turned off by studies on artificial sweeteners, have switched to bottled water, teas and energy drinks, instead. And this not the first study that has made a connection between diet soda to other serious medical issues. Several recent studies have linked diet soda and cardiovascular disease and showed a correlation (if not a causation) between cancer and aspartame. The beverage industry says people who are overweight and already at risk for heart disease may consume more diet drinks in an attempt to control their weight and the Food and Drug Administration has ruled that artificial sweeteners are safe.

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The beverage industry highlights the safety of artificial sweeteners. “Low-calorie sweeteners have been proven safe by worldwide government safety authorities as well as hundreds of scientific studies,” Lauren Kane, a spokeswoman for the American Beverage Association, told MarketWatch, on behalf of industry, including Coca-Cola KO, -0.19% and PepsiCo PEP, -1.29% . Research shows that diet soda can be a useful tool as part of a weight management plan, she added. “According to the National Institutes of Health, the likelihood of developing stroke and dementia are related to age, hypertension, diabetes and genetics,” she said.

Americans now drink more bottled water than diet soda or traditional soda. Bottled-water consumption in the U.S. hit 39.3 gallons per capita last year, while carbonated soft drinks fell to 38.5 gallons, marking the first time that soda was knocked off the top spot, according to data from industry tracker Beverage Marketing Corp. But soda is still more expensive, racking up $39.5 billion in retail sales versus $21.3 billion for water, industry research group Euromonitor found. “In 2016, bottled water overtook carbonates to become the leading soft drinks category in off-trade volume terms, an astonishing milestone a decade in the making,” Euromonitor concluded.

There has also been a backlash against sugary drinks. Soda and sugary drinks may lead to an estimated 184,000 deaths among adults every year, a 2015 study by researchers at Tufts University published in the American Heart Association’s peer-reviewed journal Circulation. The study analyzed consumption patterns from 611,971 individuals between 1980 and 2010 across 51 countries. Sugar-sweetened beverages consumption may have been responsible for approximately 133,000 deaths from diabetes 45,000 deaths from cardiovascular disease 6,450 deaths from cancer, it concluded. (The American Beverage Association published a lengthy rebuttal.)