Should I Avoid Sugar if I Have Cancer?

Written by Dr. Jill Shainhouse, ND

Should I Avoid Sugar if I Have Cancer?

A Balanced, Evidence-Informed Perspective from Dr. Jill Shainhouse, ND

“Should I avoid sugar?” This is one of the most common and emotionally charged questions I hear from patients after a cancer diagnosis. It’s understandable why. Online, you’ll find strong claims that “sugar feeds cancer,” while others insist diet makes no difference at all.

The truth lies somewhere in the middle, and it’s more nuanced than you might think.

As a naturopathic doctor with a practice focus in integrative cancer care, I aim to clarify what we actually know, what is misinformation, and what practical steps can genuinely support your health.

Does Sugar Feed Cancer? The Science Explained Simply

Cancer cells do use glucose (sugar) for fuel. However, so do your healthy cells – your brain, muscles, immune system, and healing tissues all require glucose.

Here’s what the research actually shows:
● Cancer cells use sugar differently than healthy cells – they burn it quickly and turn it into lactate, even when there’s plenty of oxygen. This unusual behaviour is known as the “Warburg effect.”
● You may think that eliminating all carbohydrates from your diet would stop this process, but healthy cells are capable of making glucose from proteins and fats through a process called gluconeogenesis.
● What does matter is whether the diet promotes insulin spikes and chronic inflammation, which can influence tumour growth in some cancers.

So the problem is not sugar alone – it’s how sugar affects the metabolic environment around the cancer.

Where Sugar Becomes a Concern

While sugar itself is not a carcinogen, certain patterns matter:

1. Diets high in added sugars increase insulin and IGF-1 levels

Chronic elevation of insulin and insulin-like growth factor (IGF-1) can promote atypical cell growth and reduce apoptosis (programmed cell death). Hormone-sensitive and metabolically active cancers, such as breast, colorectal, and prostate, may be most affected by this pathway.

We can check both insulin and IGF-1 levels in your blood to see if either marker needs improvement, and adjust your diet accordingly to help bring them into a healthier range.

2. High-sugar diets increase inflammation

Systemic inflammation can impair treatment recovery and overall wellness.

3. Excess sugar displaces nutrient-dense foods

If sugary snacks replace foods rich in fibre, antioxidants, and healthy fats, the immune system and gut microbiome may be compromised.

Where People Get Misled

Myth #1: “If I eat a cookie, my cancer will grow.”

This is not true. Your body regulates blood sugar tightly, and one treat will not accelerate tumour growth.

Myth #2: “I must avoid fruit because it contains sugar.”

Fruits contain fibre, polyphenols, antioxidants, and cancer-protective compounds. Research supports fruit intake during treatment.

Myth #3: “Only ketogenic diets work for cancer.”

Ketogenic diets may be appropriate for specific cancers (GBM, some metastatic cancers under careful supervision) but are not suitable or necessary for everyone.

A More Helpful Framing: Reduce Added Sugar, Not All Carbohydrates

The goal is not to remove all carbohydrates, but to create metabolic stability. Here’s what I recommend to most patients unless there’s a specific medical reason
otherwise:

Focus on whole, unprocessed carbohydrates:

● vegetables
● fruits
● legumes

● whole grains
● root vegetables
● intact starches (e.g., quinoa, barley, buckwheat)

Limit added sugars:

● sugary drinks
● candy
● baked goods
● sweetened yogurts
● syrups and processed snacks

Pair carbohydrates with protein and healthy fats:

– This prevents sharp insulin spikes and stabilizes energy.

Support the gut microbiome:

– Fibre helps regulate blood sugar and inflammation- two critical areas in cancer recovery.

What About Completely Cutting Out Sugar?

– Some patients feel best reducing sugar dramatically, and that’s fine- as long as the diet remains nutritionally adequate. Others find extreme restriction increases anxiety, guilt, or disordered eating patterns.
– Your mental and emotional well-being matters.
– Your diet should support your healing, not create fear.

So, Should You Avoid Sugar If You Have Cancer?

– You do not need to eliminate sugar
– You should MINIMIZE added sugars and focus on whole-food sources of carbohydrates that keep insulin stable and inflammation low.

In integrative oncology, our goal is to create a metabolically balanced, anti-inflammatory internal environment while supporting treatment tolerance, immune function, and overall quality of life.

Nutrition is deeply individual- your cancer type, treatments, metabolism, and personal preferences matter. If you’d like more information on the best diet for YOU, don’t hesitate to reach out.