Health, Longevity & Biohacking

ZOE scientist says sugar is not classed as carcinogenic by WHO

Name: ZOE scientist says sugar is not classed as carcinogenic by WHO
Uploaded: 2026-07-23T15:21:00+00:00
Description: Professor Sarah Berry says evidence linking high sugar intake to cancer risk is difficult to separate from other factors in high-sugar diets, and she emphasises obesity as a likely mediator. She adds that sugar itself is not classified as a carcinogen by the World Health Organization.

ZOE Science & Nutrition · The 5 foods you’re eating every day that are more HARMFUL than sugar · July 23, 2026

ZOE Science & Nutrition

The 5 foods you’re eating every day that are more HARMFUL than sugar

"I do think that there is no strong evidence that sugar on its own, independent of excess calorie intake, independent of um obesity is a a carcinogenic. And the WHO, the World Health Organization, does not class it as a carcinogenic. So, cancer-causing agent."

Professor Sarah Berry says evidence linking high sugar intake to cancer risk is difficult to separate from other factors in high-sugar diets, and she emphasises obesity as a likely mediator. She adds that sugar itself is not classified as a carcinogen by the World Health Organization.

About this episode

ZOE host Jonathan Wolf interviews Professor Tim Spector and Professor Sarah Berry on how different forms of dietary sugar affect metabolism and health. Berry explains that the body needs glucose in the blood but does not require dietary sugar, because glucose can be produced from other macronutrients and starches are broken down into glucose. The guests focus on “free sugars” (added sugars, honey, syrups and fruit juice) versus “intrinsic” sugars within whole foods, arguing that structure and fibre slow absorption and reduce sharp glucose excursions.

Berry describes a rapid sugar-driven rise in blood glucose followed by an insulin “overshoot” that can lead to a later dip; she says ZOE research links that dip after breakfast to earlier eating and an average of about 320 extra calories consumed across the day, alongside lower energy and mood. Spector argues repeated high glucose spikes stimulate inflammation and says this has been associated with brain and mental health outcomes, while noting much evidence is observational.

On cancer, Berry says the stronger link is indirect, via excess calorie intake and obesity-related inflammation, and she adds that WHO does not classify sugar as a carcinogen. The episode also challenges common beliefs: Spector says genetics is likely the major factor in acne, and the guests advise caution with sugary drinks, fruit juice and some “healthy-looking” products such as low-fat flavoured yoghurts, breakfast cereals and sauces. A mid-episode segment promotes ZOE-branded snack bars.

Key takeaways

Berry says the body needs glucose but does not need to consume sugar to maintain blood glucose.
The guests distinguish free sugars (including juice and honey) from intrinsic sugars in whole fruit.
Berry says ZOE data links a post-breakfast glucose dip to ~320 extra calories consumed that day on average.
Spector argues repeated glucose spikes can drive inflammation that has been associated with mental and brain disorders in studies.
Berry says the stronger evidence on sugar and cancer is indirect, via obesity and inflammation, and notes WHO does not class sugar as carcinogenic.
Spector says a twin study found genetics to be the major contributor to acne, with diet a smaller factor.
They recommend checking labels for added sugars and warn that UK labels typically report total sugar rather than free vs intrinsic.