‘Diet’ beverages and other non-caloric, artificially sweetened foods and drinks may not be the healthy choice to manage weight, according to a Purdue University expert’s review of recent scientific studies.

The review, undertaken by Susan E. Swithers, a professor of psychological sciences and a behavioural neuroscientist and published 10 July in journal Trends in Endochrinology and Metabolism, found that regular consumption of ‘diet’ soft drinks could be linked to a higher incidence of health problems.

“Public health officials are rightfully concerned about the consequences of consuming sugar-sweetened beverages, such as soft drinks, but these warnings may need to be expanded to advocate limiting the intake of all sweeteners, including no-calorie sweeteners and so-called diet soft drinks,” Professor Swithers said.

“Although it seems like common sense that diet sodas would not be problematic, that doesn’t appear to be the case,” Professor Swithers said. “Findings from a variety of studies show that routing consumption of diet sodas, even one per day, can be connected to higher likelihood of heart disease, stroke, diabetes, metabolic syndrome and high blood pressure, in addition to contributing to weight gain,” she said.

Review details

The review evaluated the most recent research on whether consuming high-intensity sweeteners, despite their zero or low calories, may result in overeating, weight gain or other health problems. About 30 per cent of adults and 15 per cent of children in the US consume artificial sweeteners.

Professor Swithers, who studies ingestive behaviour and body weight – specifically the roles that artificial sweeteners and other food substitutes play in weight management and eating – said the concerns for chemical sweeteners emerged across studies that varied widely in design, methodology and population demographics. The studies applied to sweeteners such as aspartame, sucralose and saccharin.

One study reviewed by Professor Swithers, known as ‘the San Antonio Heart Study’, reported an increase in body weight gain for adults and adolescents who consumed artificially sweetened beverages over beverages regularly sweetened. Data from a number of other studies, including the Nurses’ Health Study and the Health Professional Follow-up Study, also reported greater risk of type 2 diabetes, high blood pressure, heart disease and metabolic syndrome, which is related to diabetes and cardiovascular problems, for consumers of artificially sweetened beverages. Professor Swithers said some data indicated that those who consumed artificially sweetened beverages had double the risk of metabolic syndrome compared to non-consumers.

Artificial sweeteners may ‘confuse’ body’s ability to manage calories

Research reviewed by Professor Swithers also showed that non-caloric or reduced-calorie food and beverages “interfered with a body’s learned responses”.

Studies from Professor Swithers and colleagues, as well as other studies, showed that frequent consumption of high-intensity sweeteners may confuse the body’s natural ability to manage calories based on tasting something sweet.

“The concern that these non-caloric sweeteners might not be healthy is a message that many people do not want to hear, especially as the prevalence of artificial sweeteners increases in other products,” Professor Swithers said.

Beverages becoming “political issues”

Professor Swithers said there was “a lot of pressure” from the public health sector to find solutions to counter the rise of obesity and chronic disease, and that “there is a lot of money and business at stake for the food industry as it develops and promotes these products”.

“Beverages are becoming political issues as government leaders and politicians seek regulation and taxing to limit their availability and consumption, but most of these measures exclude diet soft drinks because they are perceived as healthy. When it comes to making policy decisions, it’s more important than ever that the science is considered and that the public understands what the science says in order to help them make the best health decisions,” she said.

Challenges for future research

Expanding studies from animal models to humans is one of the challenges for researchers trying to answer questions about how diet drinks affect humans, according to Professor Swithers. Existing studies that show specific mechanisms and metabolic causes are from animal models.

In human studies, researchers can only see correlations and are not able to identify specific causes. Professor Swithers also said that because of how “ubiquitous sweeteners have become in the mainstream diet” it is difficult to create well-designed studies.

“For example, what are the biological mechanisms and behavioural factors that influence this connection between diet soda and diabetes?” Professor Swithers said. “Some of the connection could be related to how people behave by saying to themselves, ‘I’m having a diet soda, so this cheeseburger is okay’. But animal work indicates that health problems can occur even without this kind of thinking,” she said.

“Since we don’t fully understand the mechanisms, we don’t really know how to reverse the consequences, and that will continue to be a problem as our population ages and the rates of chronic diseases like type 2 diabetes continue to increase,” Professor Swithers said.

Professor Swithers’ review was funded by the National Institutes of Health, and research is ongoing.

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