While there are many factors that influence cancer risk – like genetics, environmental toxins and lifestyle – nutrition is one of the most powerful and modifiable ones. That means it’s something you have control over, every single day.
 

Why sugar matters

Sugar is more than just a sweet treat. Research has shown that high sugar intake can increase the risk of many chronic illnesses, including heart disease, diabetes, and, yes, cancer. But how exactly does sugar play a role in cancer development?

Here’s the short version: Cancer loves sugar.

In fact, cancer cells are so hungry for sugar that medical professionals use a special tool called a PET scan to find tumours by tracking where sugar goes in the body.
 

How we know cancer loves sugar: the PET scan evidence

One of the clearest demonstrations of cancer’s dependence on sugar comes from a medical imaging tool called a PET scan (Positron Emission Tomography). This advanced scan is commonly used to detect and monitor cancer in the body.

Here’s how it works: before the scan, patients are instructed to fast, after which they receive an injection of a radioactive form of glucose. This specially labelled sugar travels through the bloodstream. Because cancer cells consume glucose at a much higher rate than normal cells, they rapidly absorb the radioactive glucose. When the scan is performed, areas of high glucose uptake light up, highlighting active cancer sites with remarkable precision. The more aggressively the tumour is consuming glucose, the brighter it appears on the scan. This phenomenon not only helps doctors locate tumours but also demonstrates just how metabolically active and sugar-hungry cancer cells truly are.

This process underscores a key insight: cancer cells rely heavily on glucose to grow and spread, making sugar metabolism a major target in cancer prevention and treatment strategies.
 

Sugar and insulin: a dangerous duo

When we eat foods that are high in sugar or refined carbs (like white bread, sweets or even fruit juice), our blood sugar spikes. In response, the body releases insulin, a hormone that helps move sugar out of the blood and into the cells.

Here’s the problem: Cancer cells thrive in environments with high blood sugar and high insulin. This combination helps them grow faster, spread more easily and even become more resistant to treatments like chemotherapy and radiation.

Even more concerning? Eating sugar doesn’t just feed the tumour, it also weakens your immune system. Just one sugary snack can reduce your immune cells’ ability to fight disease by up to 50% for hours after consumption.
 

How a low-sugar lifestyle helps

Reducing sugar in your diet can:

• Starve cancer cells of their favourite fuel source
• Lower inflammation in the body (which cancer loves)
• Strengthen your immune system
• Improve your body’s response to treatment

The ketogenic diet: a powerful tool

One dietary approach that’s gaining a lot of attention in cancer research is the ketogenic diet. This is a very low-carb, high-fat eating plan that shifts the body from burning sugar to burning fat for fuel.

Here’s how it works:

• When you stop eating carbs, your blood sugar drops.
• Your liver starts producing ketones from fat.
• Healthy cells can use ketones for energy, but cancer cells usually can’t.

This puts cancer cells under metabolic stress, making them weaker and more vulnerable. Studies show that when combined with traditional treatments (like chemotherapy or radiation), the ketogenic diet may help improve outcomes and even reduce the side effects of treatment.

The metabolic shift from glucose to ketones has been shown to:

• Slow tumour growth
• Reduce the formation of blood vessels feeding the tumour (angiogenesis)
• Trigger cancer cell death (apoptosis)
• Reduce inflammation in the body

It’s not a cure, but it’s a game changer

To be clear, this doesn’t mean diet alone will cure cancer. But it’s an incredibly powerful tool that can support your body and work alongside medical treatments.
 

What you can do starting today

If you want to create an environment in your body that’s less friendly to cancer:

• Cut back on added sugars and refined carbs.
• Avoid sugary drinks, fruit juices and processed snacks.
• Focus on whole foods: leafy greens, healthy fats, clean proteins and low-carb vegetables.
• Consider speaking with a nutritionist about whether a ketogenic or low-carb diet may be appropriate for your situation.

The Bottom Line

Cancer has a serious sugar addiction and it’s using it to grow, spread and survive. High glucose and insulin levels don’t just feed cancer; they create the perfect storm for its progression.

The good news? You can fight back. Cancer may be clever, but your body is even smarter when you give it the right fuel. By lowering sugar intake and shifting to a fat-burning metabolism through a ketogenic diet, you may be able to make your body a much harder place for cancer to thrive.

Reducing sugar intake isn’t just about weight or willpower; it’s about reclaiming your health at the cellular level. By understanding how sugar affects cancer, you can make more empowered choices every day. Nutrition is a powerful tool, but it’s not one-size-fits-all. If you or a loved one is dealing with cancer, don’t rely on internet advice. Speak to a qualified nutritionist to help you make safe, informed decisions that support your health and treatment plan.