National panel of experts says limit low-calorie sodas, stick to water instead

Monday, August 13, 2018

Data on the health effects of low-calorie sweetened beverages is lacking, and experts say we should probably cut back.

A group of leading nutritionists, doctors and researchers caution against the regular and long-term consumption of diet beverages, especially for children. In a science advisory published July 30 in Circulation, the group recommends that people drink more plain or carbonated water instead. The American Heart Association convened the expert group, which includes Jennifer Otten from the University of Washington School of Public Health.

photo on bike
Jennifer Otten

“This science advisory is based on the best available evidence, which is surprisingly quite limited,” said Otten, associate professor of environmental and occupational health sciences and core faculty in the Nutritional Sciences Program at the UW School of Public Health.

Over two years, the group mulled over dozens of studies on the links between low-calorie sweetened drinks and weight gain, diabetes, dementia, stroke and other health problems. Experts concluded that the science on diet fizzy drinks such as Diet Dr. Pepper, Coca-Cola Zero and Fresca was still too fuzzy.

Some data suggest that drinking these beverages over a long period may increase the risk of type 2 diabetes and cardiovascular disease. However, the expert panel warns, “reverse causality and adiposity cannot be ruled out as driving factors in the observations.” This means that the cause and the effect might be misidentified, or the severe overweight or obesity of study participants may affect the outcome. The link between diet sodas and stroke risk was more consistent across cohorts.

What’s more, clinical trial evidence is severely lacking. The longest randomized, controlled trial available provided an 8-ounce can every day of either low-calorie or sugar-sweetened beverages to children, ages 4 to 11 years, for 18 months. Children who were given sugary drinks gained slightly more weight, measured by Body Mass Index, than children who were given low-calorie drinks.

Low-calorie sweeteners refer to both zero- and reduced-energy food additives. This includes six sweeteners approved by the U.S. Food and Drug Administration, such as saccharin and aspartame, and two additional sweeteners: steviol glycosides, obtained from the leaves of the stevia plant, and extracts from the Swingle fruit, a small melon-like plant from Southeast Asia.

The advisory acknowledges that adults who regularly drink sugar-sweetened beverages might use diet drinks as a good alternative to reduce their sugar intake. Short-term evidence suggests that replacing sugary drinks with diet drinks could be helpful to those who are overweight or obese. The advisory was more cautious in its advice for children because there is “virtually no data” on the long-term effects of low-calorie drinks, said advisory author Frank Hu, chair of the nutrition department at  Harvard T.H. Chan School of Public Health and professor of nutrition and epidemiology.

“One question we discussed is whether for children who are obese and who drink regular soda on a regular basis, is it OK for them to drink diet soda instead?” Hu said. “The consensus is that for short-term weight control, it’s OK. Certainly, it’s not the best alternative … because we all know there are more healthy alternatives, such as water, low-fat and fat-free milk.” 

The report included an exception for one specific population: children with diabetes. The authors say those children who eat a balanced diet and who are closely monitoring their blood sugar may help keep their levels in check by substituting low-calorie drinks for sugary ones when needed.

Investigators stressed that these results need to be interpreted cautiously, as more research is needed. In the U.S., low-calorie drinks make up 32 percent and 19 percent of the beverages adults and children consume, respectively. Encouragingly, the experts pointed to federal data based on self-reported surveys showing adults and young people already are drinking less of both sugary and diet drinks.

“The advisory concluded that we need to limit low-calorie sodas and drinks and choose water instead, especially in children for whom we don’t know the long-term effects of consumption,” said Otten.

Other panel members include Rachel Johnson from the University of Vermont, Alice Lichtenstein from Tufts University, Cheryl Anderson from the University of California at San Diego, Jo Ann Carson from the University of Texas, Jean-Pierre Despres from Centre de Recherché de l’Institut Universitaire de Cardiologie et de Pneumologie, Penny Kris-Etherton from Pennsylvania State University, Amytis Towfighi from the University of Southern California and Judith Wylie-Rosett Albert Einstein College of Medicine.

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