New research on the potential health benefits of fizzy water has revealed some surprising positives - but also some negatives.
The study suggests sparkling water could help people lose weight by increasing glucose uptake and boosting metabolism, but researchers and other experts said the effect, in reality, is minimal to none.
However, sparkling water could help weight loss in more indirect ways, experts said, while warning of some potential negatives.
The research, published in BMJ Nutrition Prevention & Health, investigated claims that sparkling water was a potential slimming aid by speeding up digestion and lowering blood sugar levels.
Researcher Dr Akira Takahashi said: “While many advocate for its benefits, it is important to explore the underlying mechanisms more closely.”
To test this idea, Dr Takahashi compared the process of drinking sparking water to haemodialysis, where blood is filtered to remove waste and excess water. In that process the blood turns alkaline, producing carbon dioxide.
In a similar process, the carbon dioxide in fizzy water gets absorbed through the stomach lining and gets converted to bicarbonate - an alkaline - in red blood cells.
Dr Takahashi said the alkalinisation process speeds up glucose absorption in red blood cells, adding: “However, the amount is so small that it is difficult to expect weight loss effects solely from the CO2 in carbonated water.”
He said a balanced diet and regular exercise remained the “crucial components of sustainable weight management”.
Dr Takahashi noted there were some potential negative effects from drinking carbonated water, particularly for those with sensitive stomachs.
“The primary concerns include bloating, gas and, in some cases, exacerbation of certain symptoms associated with digestive disorders, such as irritable bowel syndrome or gastro-oesophageal reflux disease,” he said.
“Moderation is key to avoiding discomfort while still enjoying the possible metabolic benefits of carbonated water.”
Catherine Collins, an intensive care unit dietitian for the NHS, said Dr Takahashi had reviewed older research of his on dialysis for this short report and in healthy people who were not suffering end-stage kidney disease, a fizzy drink would have little effect on blood PH levels.
“Can carbonated water support weight loss? is bound to be of interest at this time of the year, but – spoiler alert - the short answer from this UK dietitian is a robust ‘NO’,” she said.
“However, substituting zero-calorie fizzy water to replace calorific drinks may aid weight loss as part of a calorie-controlled diet, by reducing calorie intake. Taking a fizzy drink with meals has in some research reduced calorie intake by inducing feelings of ‘fullness’, but in other studies have shown to increase appetite.”
Ms Collins said sparkling water was a low-calorie way to stay rehydrated, but warned plain water might be better for dental health.
“Its natural acidity derived from dissolved CO2 bubbles, is not as ‘tooth-friendly’ as plain water varieties,” she said.
Professor Keith Frayn, emeritus professor of human metabolism and emeritus fellow at Green Templeton College at the University of Oxford, said the study was a short theoretical report, with “no experimental data to support a claim that fizzy drinks may aid weight loss”.
“If fizzy drinks were to be shown to lead to weight loss, it would much more likely be through effects on feelings of fullness,” he said.
“In the meantime, however, sugar-sweetened fizzy drinks are recognised as a source of excess calories and likely to do just the opposite.”
