Does switching to ‘diet’ soft drinks really improve your health?

A University of Sydney study that models a sugar to diet beverage switch in rats suggests swapping to artificially sweetened beverages may help improve metabolic and cognitive impairments that result from too much sugar.

The study, published in Physiology and Behaviour, includes two experiments designed to assess the effect on female rats of switching to either water or an artificially sweetened saccharin-based solution following unrestricted access to a sucrose-based sugar solution.

Co-author Dr Kieron Rooney said the results were largely positive with both the groups that switched to water or artificial sweetener recovering abilities they had lost as a result of excessive sugar consumption. Yet he notes the capacity to recover may be dependent on the amount of time spent consuming sugar before quitting.

“In the first experiment where rats consumed sugar for only four weeks before switching, the rats were protected against the reduced insulin sensitivity that accompanies prolonged consumption of sugar,” said Dr Rooney from the University’s Faculty of Health Sciences and Charles Perkins Centre.

Insulin sensitivity determines how the body responds to insulin and in turn how much insulin is needed to maintain suitable blood sugar levels.

“In the second experiment when rats were consuming sugar for longer, they only partially recovered insulin sensitivity yet total body fat was reduced and rats regained the ability to rememberthe location of an object.”

At the end of Experiment 2, the groups switched to water or saccharin both recorded a similar metabolic profile in terms of weight gain, insulin sensitivity and body fat. On some measures they did not differ from the rats that had never been given the sugar solution.

Although the results can’t be directly applied to humans the researchers suggest the study is important because it replicates the switch from sugar to artificial sweetener, which is how sweeteners like saccharin are marketed.

Senior author Emeritus Professor Bob Boakes from the Faculty of Science said it’s generally accepted that high consumption of sugar-sweetened beverages is a risk factor for weight gain and associated metabolic diseases. However, he said there is ongoing debate about whether this risk is reduced by switching to artificially sweetened beverages.

“Given the controversy over diet drinks, it’s notable that switching from sugar to a solution containing an artificial sweetener like saccharin produced the same improvement as switching from sugar to water,” said Professor Boakes.

Dr Rooney said, “Our data suggests that the capacity to recover from the damage caused by excess sugar consumption is influenced by the amount of damage or length of exposure.”

“So while it is important to reduce sugar consumption to improve health, the benefits are likely to be greater if we can get children and young adults to quit before some irreparable damage is caused.”

Saccharin in an artificial sweetener commonly reported in animal studies to promote weight gain and development of diabetes, but it is not as commonly consumed by humans as other sweeteners such as aspartame, sucralose and stevia, which may have different effects on metabolism.

The researchers also caution that similar results were not found in previous studies with male rats and say further research is needed to explore the potentially protective effect of estrogen on diet.

There are two key arguments in the debate around artificially sweetened beverages. The first is the sweet calorie or ‘sweet-tooth’ hypothesis, which suggests consuming something sweet without the associated calories can lead to increased desire for sweet and energy-dense food and drinks.

Professor Boakes said the current study did not show any evidence of this.

“The consumption of the artificial sweetener in an animal with prior exposure to sugar did not result in the overconsumption of food and subsequent weight gain,” said Professor Boakes.

The second argument is that artificial sweeteners are associated with development of type 2 diabetes and weight gain. However, in this model where artificial sweetener was only fed to already obese animals the researchers did not see any exacerbation of body weight or progression to type 2 diabetes, rather they noted a positive effect.

The study was supported by Australian Research Council discovery grants. Research involving animals at the University of Sydney is approved by an Animal Ethics Committee, in accordance with the Australian code for the care and use of animals for scientific purposes.