For more than a decade we’ve been warned about the health risks of sugar-sweetened drinks, which have been linked to increased risk for heart attacks, strokes, diabetes and obesity. A new Harvard study reported that the more of these beverages people drink, the higher their risk for premature death, particularly from cardiovascular disease (CVD) and, to a lesser extent, cancer.

The same study found that replacing sugary drinks with artificially sweetened beverages (ASBs), such as diet soda, moderately reduced risk for early death, except when ASBs were consumed in large amounts. However, an earlier study tied drinking even one diet soda a day to higher risk for heart attacks, strokes and other CV events. Who is right — and how dangerous are three billion gallons of diet soda Americans drink every year?

How credible are these studies, and how were they conducted?

The Harvard study, published in April in Circulation, included 37,716 men participating in the Health Professional’s Follow-up study and 80,647 women from the Nurses’ Health study. All participants were healthy at the start of study and filled out health and lifestyle questionnaires every two years. The following results were adjusted for a number of possible cofounding factors:

  • Compared to people who drank sugar-sweetened beverages less than once a month, those who consumed two or more servings daily had a 31% higher risk of early death from CVD.
  • Each additional serving of sugary drinks daily raised risk for CVD-related death by 10%. There was also a modest link between consuming these drinks and early death from cancer.
  • ASBs only raised risk for early CVD-related death if participants drank four or more servings a day and had no effect on cancer deaths.

An earlier study, published in Journal of General Internal Medicine in 2012, analyzed the effects of regular and diet soft drinks on 2,464 people in the Northern Manhattan Study. After controlling for numerous risk factors, the researchers found that drinking one or more diet drinks daily (versus none) raised risk for heart attack, stroke and death from CV causes by 43%. In March 2019, two of the researchers also reported that drinking ASBs has been shown to cause sugar cravings, overeating and weight gain and may have adverse effects on the health of the gut microbiome.

Both studies were observational and not designed to establish a cause-and-effect relationship between soft drinks and health risks, just an association.

What do other studies say about diet drinks and health?

Another new study, conducted by the American Heart Association and American Stroke Association, analyzed data from 81,714 postmenopausal women participating in the ongoing Women’s Health Initiative Observational Study. Participants filled out questionnaires and also had periodic clinic visits and blood tests to monitor their health. Compared to women who drank diet beverages less than once a week or not at all, those who quaffed two or more diet beverages daily were:

  • 31% more likely to have an ischemic (clot-caused) stroke
  • 29% more likely to develop CVD
  • 16% more likely to die from any cause during the 12-year study
  • Heavy consumers of ASBs were at up to 240% higher risk for stroke

Previous research has shown a link between diet drinks and risk for stroke, dementia, diabetes, and metabolic syndrome, a cluster of abnormalities that triples risk for heart disease and quadruples it for diabetes. Artificially sweetened drinks have also been linked to an increased threat of osteoporosis, the brittle bone disease that can lead to fractures in older adults. Some studies also suggest that diet soda drinkers may be more likely to develop high blood pressure, the leading risk factor for stroke and a major contributor to CVD.

What’s the BaleDoneen takeaway?

Despite finding a link between drinking ASBs and increased risk for early death from cancer, the Harvard researchers suggest that it’s a good idea for people to “consume [artificially sweetened beverages] in moderation to improve overall health and longevity.” We couldn’t disagree more! Many well-done studies, including the Northern Manhattan Study discussed above, have shown that these nutritionally worthless beverages can actually be lethal, by putting people at significantly higher risk for heart attacks, strokes and early death from CVD or cancer.

Nor are diet drinks effective for weight loss, since multiple studies have linked drinking them to higher risk for obesity and associated conditions, such as insulin resistance, the root cause of  70% of heart attacks and almost all cases of type 2 diabetes. Instead, we stand strong that the best liquid is water, which is good for both your heart and your teeth.

Indeed, a six-year study of more than 20,000 people found that those who drank five or more glasses of H2O daily had half the risk of developing fatal heart disease than those who swigged two or fewer glasses a day, even when other risk factors were taken into account. To stay well hydrated, we advise drinking one-half of your body weight in ounces of water daily (75 ounces daily for a 150-pound person, for example.) Try our fruit and herb infused water recipes for a refreshing, calorie-free thirst quencher that’s good for your heart and your waistline!