Sugar and Cancer

We have all heard the refrain: Don’t eat that! Sugar feeds cancer! Recently, I have heard two specific and very different stories related to this. One story is of a woman who was at the coffee hour after church. She had taken some pastries to accompany her coffee, and a woman (whom she barely knows) told her emphatically that she should not eat those pastries for the above reason.

The second story is of another woman who told me that at her first appointment with her breast surgeon, the doctor warned her away from sugar. That second story is especially distressing because a physician should know better. The physician should know both that the equation is not that simple and that it is not fair for a physician to scare a new patient that way.

The belief that sugar feeds cancer has been around for a long time. A hundred years ago, it was reported that cancer cells consume more glucose than healthy cells, and that observation set it all in motion. Recent surveys have found that almost a third of cancer patients have heard this prohibition and try to avoid eating any sugar.

Some experts believe that eating a lot of added sugar over a lifetime may increase one’s risk of getting cancer, but deleting sugar from one’s diet does nothing to fight any cancer that is already there. Remember that every single cell in our bodies—from our brain to blood to eyes to skin—requires glucose. It is a necessary part of our body’s mechanics.

There has never been evidence that sugar is a carcinogen; that is, it cannot directly cause cancer the way that asbestos exposure or smoking can. Eating too much sugar may be unhealthy in several ways, such as causing chronic inflammation that might damage some cells and perhaps lead to diabetes or obesity. We know that obesity is a risk factor for some cancers, like breast cancer (because estrogen lives in fat cells), and that maintaining a healthy weight is important in many ways.

There has been some evidence that patients who eat diets with high amounts of added sugars have worse prognoses; this has been seen in breast, prostate, and colon cancers. We also know that women with poorly controlled diabetes have worse outcomes with breast cancer.

Sugar is naturally found in many foods, including fruits, vegetables, and some dairy products. It would be almost impossible, and certainly unwise, to eliminate them all from one’s diet. Added sugar in baked goods, sodas, or some commercially prepared foods are more often identified as harmful.

As always, the best advice is to eat a healthy diet with an emphasis on plant-based meals, less red meat, low alcohol consumption, and all the other things that we all already know. And please continue to enjoy a dish of ice cream or a slice of cake on occasion.