Take another sip of that diet coke - a new study suggests diet soda drinkers don't eat any more sugary or fatty foods than people who stick with water instead.
Some researchers have proposed drinks sweetened with fake sugar might disrupt hormones involved in hunger and satiety cues - causing people to eat more. Others hypothesised diet beverages could boost the drinker's preference for sweet tastes, translating to more munching on high-kilojoule desserts.
"Artificial sweeteners are a lot sweeter than regular sugar, on the order of 250 times sweeter, so that's where the concerns came from," said Vasanti Malik, a nutrition researcher from the Harvard School of Public Health in Boston.
What the experts say
The new findings may ease some of those worries, according to researchers led by Carmen Piernas, from the University of North Carolina at Chapel Hill Gillings School of Global Public Health. But they don't prove pounding back diet drinks is harmless.
The study included 318 overweight or obese adults in North Carolina, all of whom said they consumed at least 1176 kilojoules’ worth of drinks each day. Piernas and her colleagues advised one-third of the participants to substitute at least two daily servings of sugary beverages with water. Another one-third was instructed to substitute them with diet drinks, including Diet Coke, Diet Mountain Dew and Diet Lipton Tea.
After three and six months, people reported their food and beverage intake on two different days in detail. A previous publication showed participants in both groups lost weight. According to the new report, water and diet beverage drinkers reduced their average daily kilojoules relative to the start of the study, from between 8400 and 9660 kilojoules to 6300 to 7560 kilojoule.
What the participants were eating
At both time points, people in the two groups were eating a similar amount of total kilojoule, carbohydrates, fat and sugar, the research team reported in the American Journal of Clinical Nutrition. Six months in, the only differences were that members of the water group ate more fruit and vegetables and people randomised to diet beverages ate fewer desserts, compared to their diet habits at the study's onset.
"That's sort of the opposite of what you would expect if consumption of diet soda increased the preference for sweets," Malik, who wasn't involved in the new study, told Reuters Health. The research was partially funded by Nestle Waters USA, which provided the water used in the study.
Despite the results, diet beverage drinkers may not be totally in the clear. Another new study, also published in the American Journal of Clinical Nutrition, found Frenchwomen who drank beverages sweetened with either real or fake sugar were more likely to be diagnosed with diabetes over 14 years than those who stuck with water.
Findings in the studyPiernas cautioned that everyone in her study was heavy and trying to lose weight - so the findings may not apply to normal-weight people who drink a lot of diet beverages."This is not the final answer," she told Reuters Health.
Some studies have suggested an increased risk of cancer tied to certain artificial sweeteners, but convincing evidence is lacking, according to Malik."We're trying to reduce sugar-sweetened beverage intake in the population for obesity, so the next logical question is: what substitutes can be used?" she said."I think (diet drinks) can be consumed in moderation, along with other beverages - water, coconut water, sparkling water, that type of thing," Malik added.