Does Sugar Feed Cancer?

If sugar “feeds” cancer, can I starve cancer from my body with diet?

Cancer is a complex disease that may develop as a result of a variety of environmental and genetic factors, so does sugar feed cancer? While we understand that diet may play a role in increasing risk for certain types of cancer in some people, it is extremely difficult, if not impossible, to rule a single nutrient as “cancer causing” for an entire population.

Perhaps one of the most problematic misconceptions about cancer and diet is the idea that dietary sugar “feeds” cancer cells. In that vein, many assume that by eliminating sugar from the diet we can effectively cure disease.

While this premise may be rooted in scientific fact (as I will discuss below), the idea that eliminating a single nutrient from the diet will treat and cure cancer is both overstated and dangerous.

In this blog, I’ll explain the science behind sugar “feeding” cancer and what makes cutting sugar and carbohydrates from your diet altogether a bad idea.

Getting to know glucose

Our bodies run on glucose, a fancy word for sugar. Glucose is the fuel that powers every single one of our cells, from head to belly to toe. Our brains require the most fuel, accounting for up to 60% of our glucose utilization. You could think of your brain as an expensive sports car in the sense that it runs on premium glucose fuel only.

Cancer cells are no different from normal cells in that they also require glucose to grow and multiply. However, unlike normal cells, cancer cells grow and divide more rapidly, meaning they use up a lot more glucose than normal cells.

In the most simplistic sense, it may seem logical that in order to slow down and kill cancer cells you could starve them of their favorite food, glucose.

“Starving” cancer is a problematic nutrition myth

The problem with the idea of “starving” cancer by cutting out sugar is four-fold:

1. There’s no way for our bodies to redirect glucose away from cancer cells and give it to only normal, healthy cells. To truly stop “feeding” cancer, you would have to stop feeding all your healthy cells too.

During cancer treatment especially, your body is relying on your normal, healthy cells for strength– starving them is the worst thing you could do.

2. Glucose (sugar) doesn’t just refer to the granulated white stuff, candy, and soda. Glucose is derived from all carbohydrate-containing foods, many of which are nutrient-dense and belong in a varied, balanced diet.

Cutting carbohydrate foods from your diet like whole grains, dairy, fruits, vegetables, and legumes (all of which are broken down to glucose in the body) can result in:

• Nutrient deficiencies and malnutrition
• Increased fatigue and decreased strength
• Dangerous, treatment-altering weight loss

3. Our bodies have an advanced fail-safe mechanism that prevents glucose levels in the body from dropping to levels of 0, even if you cut it from your diet (remember, it’s the body’s preferred fuel and our brain’s only fuel source).

When sugar stops coming in from dietary sources, our bodies break down proteins from muscle tissue and convert it to glucose in order to fuel cells. Again, the breaking down of healthy, lean body mass is counterproductive to fighting cancer.

4. Cutting carbohydrates has been shown to increase cortisol (the stress hormone) levels in the body which can lead to compromised immune function and increased systemic inflammation.

In short, our bodies get stressed when not fueled adequately and that stress can lead to poorer health outcomes, especially during cancer treatment.

It’s important to note, too, that much of the published research on sugar and cancer cells comes from studies on in vitro (petri dish) and animal models. While this research provides important insight for future studies, it fails to establish a causal relationship between sugar and cancer growth in humans.

At this time, there is no proven clinical benefit to cancer patients by cutting sugar and carbohydrate intake.

Weight gain, inflammation, and increased risk of disease

Besides “feeding” cancer cells, sugar is often broadly implicated in weight gain. A diet with excess added sugars from nutrient-poor sources like sodas, sweets, and processed foods may result in increased body weight over time.*

Research suggests a correlation between overweight/obesity and inflammation which in turn has been associated with increased risk of cancer development.

However, as I detailed in my blog about inflammation and weight gain, diets and intentional weight loss (especially those that focus on removing entire food groups) are not a long term solution to reducing inflammation and disease risk:

• Diets and intentional weight loss only temporarily improve inflammation and reduce disease risk since upwards of 95% of diets fail
• Dieting produces short term weight loss and long term weight regain and weight cycling
• Weight cycling makes inflammation worse, worse than if you stayed at your original weight (overweight or not)

While dieting or intentional weight loss is not the best course of action to reduce harmful inflammation, focusing on incorporating healthful habits into your daily routine is. Taking a weight-neutral approach to reducing inflammation has been shown to improve long term health outcomes, including reducing disease risk.

*Weight gain in most cases is not solely attributable to diet. We acknowledge that weight gain can be the result of many environmental and genetic factors and continue to work hard to dispel the misconceptions that a “bad” diet is the sole cause of weight fluctuations and that individuals are largely personally at fault for their body weight.

A carbohydrate-friendly cancer diet approach

Assuming that one can “starve” cancer by refusing to “feed” it sugar is not based in good science. Attempting to cut an entire food group from your diet or inducing weight loss after your cancer diagnosis is dangerous and ill-advised. There is no evidence to suggest that either of these interventions will result in positive health outcomes.

Instead of avoiding sugar and carbohydrates altogether, focus on a diet that emphasizes balance, variety, and moderation:

BALANCE:

• Balance: A balanced diet contains carbohydrates– between 45-60% in fact. As discussed earlier, carbohydrates come from foods like grains, dairy, fruits, vegetables, and legumes. They also come from sodas, sweets, and convenience foods. You may find it beneficial to work with a dietitian to determine where the carbohydrates in your diet are coming from. The rest of your diet should contain proteins and fats as depicted on our Rebel Plate:

VARIETY:

• Variety: It’s ok to eat sugar in the form of a donut or a hot fudge sundae. However, the 45-60% of your diet that is made up of carbohydrates should come from a variety of carbohydrate foods, not just desserts and other sweet treats. Eating a variety of carbohydrates ensures that you receive all the beneficial nutrients like vitamins, minerals, and fiber that you need to stay strong and healthy.

MODERATION:

• Moderation: Moderation means eating enough food to feel satisfied—not too much, and not too little. Satisfaction is both physical and emotional. Some foods like cookies are enjoyable and provide satisfaction, but when eaten in large quantities are likely to make you feel physically ill, spiking blood sugar causing mood swings, fatigue, and stomach ache. Moderation will likely require you to tap into your internal hunger and fullness cues, helping you decide what foods feel good to eat and support both your physical and mental health.

You may find it useful to learn more about gentle nutrition by reading this blog.

It’s also important to note that this approach to eating does not focus on weight loss as a measure of success. In many cases, incorporating balance, variety, and moderation into one’s dietary routine can result in weight loss, which we view as a side effect, not an end-goal.

The goal of your diet to prevent or manage a cancer diagnosis should be to feel your best physically and mentally while giving your body the nutrients it needs to stay healthy and strong.

When dietary change feels out of reach

If you’ve been diagnosed with cancer and are currently undergoing treatment, the tenants of balance, variety, and moderation may feel out of reach. You are not alone. Treatment can affect appetite and chewing and swallowing ability, making eating anything at all feel like a challenge.

Now, especially, would be a terrible time to cut carbohydrates from your diet. Instead, consider reading up on some cancer diet tips and tricks that we’ve compiled [HERE: Cancer Diet Tips, Tricks and Recipes to Help You During Treatment] that might make eating with symptoms of cancer treatment a little more manageable.

In summary

Glucose (sugar) feeds all cells in our bodies, not just cancer cells.

There have been no studies published that suggest that cutting sugar from the diet will result in positive health outcomes for cancer patients. Sugar intake, weight gain, and risk of disease is also of concern for many individuals.

Diets and intentional weight loss will only temporarily decrease inflammation and risk of disease. A dietary approach that focuses on healthy habits like balance, variety, and moderation is more effective than cutting out entire food groups.

Resources about Sugar and Cancer:

Oncology Nutrition from Academy of Nutrition and Dietetics

American Institute of Cancer Research

If you are interested in learning more about sugar, cancer, and how your diet is important to your treatment and recovery, I encourage you to schedule a consultation with one of our knowledgeable dietitians.

-Blog reviewed and updated by Rebecca Bitzer MS RD LD September 10, 2021