Connecting Sugar and Cancer – What it All Means

Amongst internet searches of cancer, many of us have come across the sugar feeds cancer theory. In this post, we want to dive into what this really means and if it’s true – Does sugar cause cancer? Does it feed cancer cells, making them grow more aggressively? And how does the dietary sugar we consume affect our health, and what can be done about this?

The quick answer is that sugar does have an effect on cancer, but not in the direct way you might think or commonly read about. The sugar feeds cancer theory is over simplifying some complicated biology.

Let’s first understand what sugar is: in its simplest form, it is just a single molecule, such as glucose and fructose. Glucose and fructose are called simple sugars and can also join together to make longer chains and it is these longer chains that we call carbohydrates, which are, for most of us, our body’s main source of energy that we consume in food. Sugars exist in many foods, in both refined/processed forms (table sugar) as well as unrefined/unprocessed ones (honey). Starchy foods such as rice, bread, pasta and vegetables like potatoes might not taste sweet, but they are high in sugar in carbohydrate form too.

Sugar, in some form, is in many things we eat. And this is good, because all kinds of cells, including cancer cells, depend on blood sugar (glucose) for energy. It’s here that sugar and cancer start to collide, because cancer is a disease of cells. The sugar feeds cancer theory is a myth that simply states that if cancer cells, which divide and multiply rapidly, need lots of sugar, then cutting it out of our diet must help stop cancer from growing, and could even stop it developing in the first place. Unfortunately, it’s not that simple.

All of our healthy cells need sugar too, and there’s no way of telling our bodies to let healthy cells have the sugar they need, but not give it to cancer cells. More research is needed to understand the relationship between sugar in the diet and cancer and there is ongoing research on the ketogenic diet, however as of now, there’s no good evidence that following a “sugar-free” diet lowers the risk of getting cancer, or boosts the chances of surviving if you are diagnosed.

However, all of this does not mean that sugar isn’t a culprit in cancer. There is some evidence that consuming large amounts of sugar is associated with an increased risk of certain cancers. Eating too much sugar can also lead to weight gain and increase the risk of obesity and diabetes, which increases your risk for many cancers. Dietary sugar raises our blood sugar, which leads to increased levels of a hormone called insulin, that helps sugar get into our cells. Insulin is a growth hormone and subsequently causes an increase in insulin-like growth factors (IGFs) that have been implicated in cancerous development and growth. So, although sugar in and of itself is not the direct culprit of cancer development, its impact on the body can create an environment where cancer can easily grow.

So, what do we do? We can’t avoid all dietary sugar so ultimately, the best approach is to have a low-sugar and high-fiber diet so that we can keep our blood sugar level low, so that we keep insulin and the insulin-like growth factors low. In other words, eat less sugar and more vegetables!

When we consume whole foods, like vegetables and fruits, that contain sugar in the form of carbohydrates, we are also consuming fiber. Fiber is critical in blood sugar lowering as it slows the absorption of sugar into our blood, avoiding high spikes. It’s added sugar (found in soft drinks, sweets that have cane sugar, etc) that we’re mainly concerned with when it comes to weight gain and cancer, not sugar that is naturally found in foods like fruits, vegetables and whole grains. Remember that refined grains (white rice, white flour found in sweets, cakes, pastas, crackers, cereals, etc.) have had their fiber removed, so the carbohydrate sugar in these foods will be absorbed quickly, spiking blood sugar and subsequently, those growth factors mentioned above. Reading nutrition information labels and checking the ingredients list can help you choose lower sugar and higher fiber options.

Now, let’s be honest. Some of us have a sweet tooth and for those of us who sway towards the sweeter side, letting go of anything sweet seems like a daunting task. Listed here is a chart with the breakdown of common sweetening agents and their ability to raise blood sugar levels. Although table sugar has dramatic effects on blood sugar, some other popular alternatives are not far behind.

Common Sweetening Agent and Their Impact on blood sugar levels:

SweetenerGlycemic Index (In other words: impact on blood sugar levels per serving)
Table sugar65
Maple Syrup54
Honey50
Coconut Palm Sugar35
Agave syrup15
Stevia0
Monk fruit0

You may have noticed stevia and monk fruit have no impact on blood sugar levels. By replacing table sugar with one of these two alternatives, it can help lower blood sugar levels. Here is some more information on these natural sweeteners:

Stevia: one of the more popular zero calorie sweeteners extracted from a shrub that has been used for centuries as a sweetener and for other medicinal uses such as lowering blood sugar. This natural herbal sweetener has no calories and is up to 300 times sweeter than table sugar – so be careful before dumping a whole teaspoon into your morning coffee: it’s got kick! The taste might take some time getting used to as there is a slight bitter aftertaste.

Monk fruit: this natural zero calorie sweetener gets its intense sweetness from unique antioxidants which have been shown to inhibit proliferation of cancer cells. Meaning, on top of sweetening your morning coffee without spiking you blood sugar; monk fruit may help to combat cancer. But be careful! These antioxidants make monk fruit a potent sugar substitute, although many find it more palatable than stevia.

So the take home message is that although banishing sugar won’t stop cancer in its tracks, we can choose foods that contribute to an anti-cancer terrain in the body. In committing to lessen your sugar intake, you will help to re-calibrate the body’s composition, and you may also feel more stable energy throughout the day, as well as improved sleep and immune function.

Author: Sophia Sokolowski, CCNM Integrative Cancer Centre intern