Despite the claims of the “diet” soft drink industry, researchers have found no good, consistent evidence that artificially sweetened beverages help people maintain a healthy weight, according to a commentary published last week in the journal PLOS Medicine.
In fact, the contribution of such beverages to the global epidemic of obesity and related health problems may be just as bad as that of their sugar-laden counterparts, argue the commentary’s authors.
Artificially sweetened beverages may also be having a negative impact on the world’s environment, the authors add.
“A common perception, which may be influenced by industry marketing, is that because ‘diet’ drinks have no sugar, they must be healthier and aid weight loss when used as a substitute for full sugar versions,” said Christopher Millett, one of the commentary’s authors and a professor of public health at Imperial College London, in a released statement. “However, we found no solid evidence to support this.”
Yet, as Millett and his co-authors point out, individuals — and policymakers — continue to act as if such beverages are healthy alternatives to ones with added sugar, which is why they now compose approximately a quarter of the global soft drink market.
It’s also why artificially sweetened beverages tend to be excluded from taxes and regulations aimed at their sugary counterparts — and why they are often not mentioned or sometimes even promoted in dietary guidelines.
Plenty of caveats
Eating foods and beverages with added sugar has been identified as a major cause of the dramatic global increase in obesity and type 2 diabetes during the past few decades. In the United States, almost half of added sugar comes from the ingestion of sugar-sweetened beverages, including carbonated soft drinks, fruit-flavored drinks, sports/energy drinks and ready-to-drink coffee and teas.
In recent years, sales of sugary, calorie-laden beverages (particularly soft drinks) have been on the decline, a drop spurred no doubt by messages about their unhealthfulness. The beverage industry has responded by aggressively promoting artificially sweetened beverages as healthful alternatives.
For the current commentary, an international group of experts from the United Kingdom, the United States and Brazil reviewed and assessed the existing research on artificially sweetened beverages and health. They conclude that the evidence regarding the long-term impact of such beverages on weight management and related health outcomes, such as obesity and type 2 diabetes, is limited at best.
Most of the studies to date that have shown positive (healthy) outcomes, such as weight loss, from consuming artificially sweetened rather than sugar-sweetened beverages have been observational, and thus their findings cannot be considered definitive, the researchers note. The randomized control trials that have looked at the effect of artificially sweetened beverages on weight management, they add, have had mixed results, with some showing no effect and others showing a modest reduction in weight.
In addition, the randomized trials often come with many caveats, such as short follow-up periods and small numbers of participants, which make their findings problematic.
Perhaps the biggest caveat, however, is that much of the research on artificially sweetened beverages is industry-sponsored, which raises the potential for bias. Indeed, as Millett and his colleagues point out, industry-sponsored studies are more likely to report favorable results and conclusions about both sugar-sweetened and artificially sweetened beverages’ effects on weight control than non-sponsored studies.
“These findings underscore the substantial and complex nature of bias from conflicts of interest in [artificially sweetened beverages] research,” they write.
Why would artificially sweetened beverages be as problematic as sugar-sweetened ones, despite containing no (or few) calories?
Some research suggests that artificial sweeteners may stimulate sweet taste receptors in the brain, which may lead people to overeat other foods — and thus put on weight. In addition, artificial sweeteners “may contribute to the development of glucose intolerance by altering the composition and functions of gut microbiota,” Millett and his colleagues write.
The commentary’s authors stress, however, that research pointing to these negative outcomes is far from conclusive.
“The available evidence does not directly support a role of [artificially sweetened beverages] on inducing weight gain or metabolic abnormalities but also does not consistently demonstrate that [artificially sweetened beverages] are effective for weight loss or preventing metabolic abnormalities,” they write.
Yet another concern
One area of research that deserves much more attention is the impact of sweetened beverages, including artificially sweetened ones, on the environment, say Millet and his colleagues.
“High consumption of sweetened beverages leads to high generation of solid waste and cumulative chemical pollution, affecting marine life and contaminating the food chain, which raise concerns regarding food safety for human health,” they write.
“Artificial sweeteners have been recently recognized as an emerging environmental contaminant of the aquatic environment,” they add. “Households, small businesses enterprises, and industry contribute to releasing sweeteners into the aquatic environment, with scarce research on their ecotoxicological profile and consequences for planetary health.”
Risk remains unknown
The commentary’s overall argument boils down to this: We don’t know enough yet about the role of artificially sweetened beverages in human health — or in the health of our environment — to be treating these products as innocuous.
“The absence of evidence to support the role of [artificially sweetened beverages] in preventing weight gain and the lack of studies on other long-term effects on health strengthen the position that [artificially sweetened beverages] should not be promoted as part of a healthy diet,” the researchers conclude.
“Far from helping to solve the global obesity crisis,” they add, “characteristics related to [artificially sweetened beverage] composition (low nutrient density and food additives), consumption patterns (potential promotion of sweet taste preference), and environmental impact (misuse of natural resources, pollution, or ecotoxicity) make them a potential risk factor for highly prevalent chronic diseases.”
FMI: You can read the commentary in full on the PLOS Medicine website.