Scientifically Speaking | The bitter truth about non-sugar sweeteners

In my column last week, I discussed how many steps we need to stay healthy. This week, I talk about changing scientific views on using non-sugar sweeteners.

Who doesn’t want to be healthier? We’ve been told for many years to cut down on our consumption of sugar, and many of us embraced non-sugar sweeteners. But there’s an emerging consensus that non-sugar sweeteners are not a healthy option. In fact, the World Health Organization (WHO) released guidelines in 2022, advising against using non-sugar sweeteners for weight control or to reduce the risk of diseases commonly linked to obesity, such as diabetes and heart disease.

Sugar and artificial sweeteners have shown negative effects linked to obesity and diabetes during research.(Shutterstock)

So, how did we get here and what’s the science behind the changing views?

With obesity linked to severe health risks, health experts advised cutting down on free sugars. Around two decades ago, I started to consume soft drinks and beverages containing non-sugar sweeteners, believing their zero-calorie content shielded me from the health risks associated with sugar. At the time, the belief held by most was that these sweeteners were, at worst, harmless inert compounds that gave us the sensation of sweetness we craved without the calories of sugar.

Non-sugar sweeteners include artificial options like aspartame and saccharin, and natural ones like stevia. They're popular for their promise of helping with weight loss because they don't have the calories that sugar does. You can find them in a variety of products, from soft drinks and sweets to toothpaste, often chosen by those trying to cut down on sugar.

However, a series of scientific investigations in the past few years has urged us to reconsider our consumption of non-sugar sweeteners. The 2022 WHO guidelines were based on a review of over 280 studies, including randomised controlled trials and observational studies, which painted a complex picture of the impact sweeteners had on the health of people.

While short-term benefits, like reduced calorie intake and minor weight loss, were observed with non-sugar sweetener use, observational studies linked long-term non-sugar consumption with increased risks of obesity, diabetes, heart disease, and even early death.

To be clear, there’s no established causal link between non-sugar sweeteners and these adverse outcomes. The evidence is compelling, but far from definitive. But the evidence keeps mounting that these sweeteners are not good for us.

The reasons behind the potential health risks of non-sugar sweeteners are not entirely clear yet. It's possible that although non-sugar sweeteners taste sweet, they might not reduce calorie intake as expected. This could be because they affect our sense of hunger, change our taste preferences, or alter the balance of bacteria in our gut, which could influence weight and health.

I have been digging into a few of these studies, and the results are compelling. In 2022, research published in the scientific journal Cell explored the effects of artificial sweeteners on the human microbiome and glucose tolerance. The microbiome is the collection of microbes that are essential for our health. Research on healthy adults showed that sweeteners such as saccharin and sucralose negatively affected response to glucose. This study also found that people varied in how their bodies dealt with artificial sweeteners based on their own metabolic health, which was tied to the microbes that were a part of their gut microbiome.

In 2023, research published in the scientific journal iScience found that non-sugar sweeteners could significantly alter the microbial diversity and composition in the duodenum, which is a part of our small intestine. This offered more evidence that non-sugar sweeteners were disrupting the normal balance of microbes in our bodies.

And then earlier this year a study published in the medical journal Circulation: Arrhythmia and Electrophysiology, involving over 200,000 participants for around 10 years found that consuming more than two litres per week of sodas containing non-sugar sweeteners raised the risk of irregular heartbeats in a condition known as atrial fibrillation. Sodas sweetened with sugar were not quite as bad, while unsweetened juices seemed to reduce the risk of atrial fibrillation.

Right now, there’s no recommended limit to how much non-sugar sweetener people should consume in the WHO guidelines, but those who use them frequently might want to cut back. The guidelines also don't apply to sugar alcohols, medications, dental hygiene products, or to people with diabetes.

Finding a sugar substitute that fulfils our craving for sweetness without the risk of potential health risks remains challenging. Until we find one, I’m going to try to enjoy unsweetened beverages such as tea without sugar and carbonated water.

Anirban Mahapatra is a scientist and the author of COVID-19: Separating Fact From Fiction. His second popular science book, When The Drugs Don’t Work: The Hidden Pandemic That Could End Medicine, will be published this year. The views expressed are personal.