“I’ve cut out all sugar, including fruits and vegetables.” 

Sugar, or more specifically glucose, is the fuel for all cells in your body. It’s the energy needed for your heart to beat, brain to think, and muscles to function. Even if you cut out carbohydrate foods your body still gets glucose by pulling it from storage supplies in the liver. So, if glucose is necessary for life, what does that mean in terms of cancer growth?  

Eating foods that contain glucose (or any type of sugar) causes the body to produce insulin. Insulin is a hormone that keeps blood sugar in check – preventing it from going too high. Just like glucose, insulin is necessary for bodily functions. But insulin is also a growth factor, so, ideally, your body would produce the amount you need but not excess. This is where the potential link to cancer comes in. The more added sugar you eat, the more insulin your body secretes.    

Before we go further, it’s important to understand the difference between naturally occurring sugars like those in fruits, vegetables, and whole grains, and added sugars, like those in sugary drinks, breakfast cereals, and desserts (among other foods). In general, fruits, vegetables, and whole grains don’t stimulate as much insulin production as added sugars. That’s because fruits, vegetables, and whole grains contain fiber, which slows down how fast that sugar gets into the bloodstream. 

Foods high in added sugar, on the other hand, usually don't contain much fiber, which means nothing else is there to slow the pace of those sugars hitting the bloodstream. Eating foods that contain higher amounts of added sugar can drum up more insulin than is desirable.  

How Insulin is Involved

Too much insulin, over time, may have an indirect impact on cancer. That’s because insulin is a growth hormone. Insulin does not cause cancer; but eating added sugar frequently can contribute to excess insulin being available for cellular growth – healthy and cancer cells. 

The Bottom Line About Sugar and Cancer

Not all sugars are equal. Fruits, vegetables, and whole grains don’t pose the same risks as sugar-sweetened beverages, cakes, cookies, and pies. Vegetables and fruits, like carrots and oranges, do not need to be avoided.  

You also don’t need to eliminate dessert altogether. When having a portion of dessert, eat it with or right after a meal that contains protein and fiber, both of which can help slow the rate at which those sugars reach your bloodstream.

How Much Added Sugar is Too Much?

The American Heart Association guidelines suggest keeping added sugar intake to less than 25 grams a day (for women) and 36 grams per day (for men). One teaspoon of sugar is 4 grams, so you might begin by paying attention to how much sugar you add to things like coffee or tea. You can also check labels on pre-packaged foods like breakfast cereal, bread, pasta sauce, crackers, cookies, condiments, and store-bought desserts. 

To find out how much added sugar is in a food, check the nutrition label. Look for the line that says, “Includes Added Sugars,” which is just below the Total Sugars on the food label. This tells you how many grams of sugar per serving have been added to that food.