Sweet treat to silent risk: How sugar may raise cancer, heart risk

Experts say refined sugars may do more than add calories because they can alter insulin response, raise cardiovascular risk and create conditions linked to cancer development

The debate around sugar has simmered for decades. While it was once centred on cavities and calories, it now includes heart disease, diabetes and cancer. Medical experts argue that the problem is not natural sugars in fruit but the overwhelming presence of added sugars in modern diets.

 

How has sugar consumption shifted over time?

 

A report by CBS News highlights evidence from studies that link high sugar consumption not just to weight gain but also to serious illnesses such as heart disease and cancer. California-based paediatric endocrinologist Dr Robert Lustig told CBS News that added sugars had become a “public health crisis” because of their widespread impact on health.

 

Central to Dr Lustig’s theory is the idea that humans once consumed fructose mainly through whole fruits, which naturally contain fibre and therefore slow down absorption while also limiting how much we eat at one time. However, as sugar and high-fructose corn syrup became cheaper to refine and produce, they were added to processed foods and drinks in far greater quantities, and people began consuming levels of fructose that the body was never designed to handle regularly.

 

He argues that while fruit in its natural form is not harmful because fibre regulates the metabolic response, refined sugars overwhelm the liver and disrupt normal metabolic processes when consumed in excess.

 

His concerns are increasingly supported by scientific research. Studies conducted by Kimber Stanhope, a nutritional biologist at the University of California, Davis, have shown that consuming high levels of fructose can increase harmful fats in the blood, raise cardiovascular risk markers and alter metabolism in ways that may contribute to heart disease.

 

The report also featured Dr Lewis Cantley, a Harvard professor and former head of the Beth Israel Deaconess Cancer Center, who explained how sugar may influence cancer biology at a cellular level. He emphasised that insulin is not just responsible for regulating blood sugar but also plays a role in cell growth and proliferation, and therefore persistently high insulin levels may create conditions in which cancer cells are more likely to thrive.

 

How excess sugar affects the body

 

Medical experts agree that sugar’s impact goes beyond empty calories. According to Dr Vineet Talwar, director of Medical Oncology at Rajiv Gandhi Cancer Institute and Research Centre, excessive sugar intake can disturb metabolic balance, weaken immune defences and encourage processes that make cancer more likely to develop.

 

• Insulin Resistance: Over time, repeated spikes in blood glucose make cells less responsive to insulin, leading to higher circulating insulin levels that can signal cells to divide more rapidly
• Chronic Inflammation: Persistent high blood sugar and insulin levels promote inflammatory processes that can damage tissues and weaken immune defences
• Hormonal Imbalance: This can disrupt normal cell function and repair systems, making it easier for abnormal cells to survive and multiply
• Oxidative Stress: Sugar metabolism can produce by-products that damage DNA and cellular structures

 

Together, these changes foster conditions in which cells that have already acquired mutations are more likely to survive and proliferate.

 

Mechanisms behind sugar and cancer link

 

A review published in the journal Cancers titled 'The role of dietary sugars in cancer risk' examined the biological mechanisms linking sugar intake to cancer risk. The authors found that high consumption of sugars like glucose and fructose may contribute to cancer development through pathways including insulin resistance, chronic inflammation, and increased formation of blood vessels that supply tumours (angiogenesis).

 

Although the evidence is still evolving, this review highlights key mechanisms that help explain sugar’s role in cancer biology:

 

• VEGF-driven Angiogenesis: Fructose may increase expression of vascular endothelial growth factor (VEGF), supporting new blood vessel growth that tumours need to thrive
• Warburg effect: Glucose metabolism in cancer cells is often altered, favouring rapid energy production that supports tumour growth
• Insulin resistance and inflammation: These chronic states create an environment conducive to cancer initiation and progression

 

How to reduce sugar without feeling deprived

 

Understanding sugar’s role isn’t about giving up sweetness forever, rather it’s about moderation and mindful choices. Some practical tips include:

 

• Limit added sugars: Choose water, tea or natural fruit over sugary drinks
• Choose whole foods: Fruits and vegetables provide sugar alongside fibre and nutrients
• Watch hidden sugars: Processed foods often contain more sugar than you expect
• Maintain a balanced diet: Eating fibre-rich and nutrient-dense meals supports stable blood sugar and metabolic health

 

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This report is for informational purposes only and is not a substitute for professional medical advice.