Scientists in Australia have discovered something surprising about diet sodas and other drinks with artificial sweeteners. Their research shows that drinking just one diet soda per day might actually increase your risk of getting type 2 diabetes even more than drinking regular soda!

What Did the Study Find?

Researchers from Monash University, RMIT University, and the Cancer Council Victoria studied more than 36,000 Australian adults for almost 14 years. Here’s what they discovered:

• Diet sodas (with artificial sweeteners): Increase diabetes risk by 38%

• Regular sodas (with sugar): Increase diabetes risk by 23%

This was shocking because most people think diet drinks are healthier than regular sodas.

Why Is This Surprising?

For years, doctors have told people at risk for diabetes to switch from regular soda to diet soda. The idea was that artificial sweeteners don’t have calories or sugar, so they should be safer.

Professor Barbora de Courten, who led the study, said: “Artificial sweeteners are often recommended to people at risk of diabetes as a healthier alternative, but our results suggest they may pose their own health risks.”

How Did They Do This Research?

The scientists used data from a long-running study called the Melbourne Collaborative Cohort Study (also known as Health 2020). They looked at people aged 40-69 years and carefully considered many factors that could affect the results, including:

• What people ate

• How much they exercised

• Their education level

• Their health history

• Their body weight

Why Might Diet Drinks Be Worse?

The researchers found something interesting when they looked at body weight:

Regular sodas: The increased diabetes risk seemed to be mostly because people who drank them gained weight, and being overweight increases diabetes risk.

Diet sodas: Even after accounting for people’s weight, the diabetes risk was still high. This suggests that artificial sweeteners might directly affect how the body processes sugar, not just through weight gain.

Robel Hussen Kabthymer, the PhD student who worked on the study, explained: “Drinking one or more of these beverages each day—whether sweetened with sugar or artificial substitutes—was linked to a significantly higher chance of developing type 2 diabetes.”

What Are Artificial Sweeteners?

Artificial sweeteners are man-made chemicals that taste sweet but don’t have calories like regular sugar. Common artificial sweeteners include:

• Aspartame

• Sucralose

• Saccharin

• Acesulfame potassium

You’ll find these in:

• Diet sodas

• Sugar-free gum

• Diet energy drinks

• Many “sugar-free” or “diet” products

Why This Matters

Type 2 diabetes is a big problem:

• About 1.3 million people in Australia have it

• More than 500 million people worldwide have it

• Most cases are linked to diet and lifestyle choices

Diabetes can cause serious health problems:

• Heart disease

• Kidney damage

• Vision problems

• Nerve damage

• Problems with wound healing

What Should People Do?

The researchers say this study has important lessons for everyone:

For Individuals:

• Don’t assume “diet” or “sugar-free” automatically means healthier

• Try to limit ALL sweetened drinks, whether they have sugar or artificial sweeteners

• Choose water, unsweetened tea, or other drinks without any sweeteners when possible

For Governments:

Professor de Courten said: “We support measures like sugary drink taxes, but our study shows we also need to pay attention to artificially-sweetened options. These are often marketed as better for you; yet may carry their own risks.”

She suggests that policies to reduce diabetes should focus on reducing ALL non-nutritive beverages (drinks that don’t provide good nutrition), not just sugary ones.

What’s the Best Choice for Drinks?

Based on this research, here are the healthiest drink options:

Best choices:

• Plain water (preferably filtered)

• Unsweetened tea or coffee

• Sparkling water with a splash of fruit juice (preferably not out of a plastic bottle)

• Milk (preferably organic – which has natural nutrients and no hormones)

Okay sometimes:

• 100% fruit juice (but it’s high in natural sugar, so drink small amounts)

• Smoothies made with whole fruits and vegetables

Try to avoid or limit:

• Regular sodas and sugary drinks

• Diet sodas and artificially sweetened drinks

• Energy drinks (regular or diet)

• Sports drinks (unless you’re doing intense exercise)

Important Things to Remember

1. This was just one study: More research is needed to confirm these findings and understand exactly why artificial sweeteners might increase diabetes risk.

2. Everyone is different: What affects one person might not affect another person the same way.

3. Overall lifestyle matters most: Eating a healthy diet, exercising regularly, and maintaining a healthy weight are still the most important things you can do to prevent diabetes.

4. Don’t panic: If you occasionally drink diet soda, this doesn’t mean you’ll definitely get diabetes. The study looked at people who drank these beverages regularly over many years.

The Bottom Line

This study challenges the idea that switching from regular soda to diet soda is automatically a healthy choice. While regular sodas are still not good for you because of all the sugar and calories, diet sodas might have their own problems.

The safest approach is to try to drink mostly water and other unsweetened beverages. If you do want something sweet to drink occasionally, pay attention to how much and how often you’re having it.

Remember: the goal isn’t to be perfect, but to make choices that support your long-term health!

Original study: Robel Hussen Kabthymer et al, “The association of sweetened beverage intake with risk of type 2 diabetes in an Australian population: A longitudinal study,” Diabetes & Metabolism (2025). DOI: 10.1016/j.diabet.2025.101665

Provided by: Monash University