I wrote here on excessive sugar consumption and why it is harmful. In a nutshell, sugar encourages many of the epidemic Western chronic diseases, including obesity, diabetes, heart disease, and dementia.
But the correlation between sugar and cancer is worth looking at in greater detail.
This study shows that those who consume more high sugar beverages have an increased risk of cancer. This is a correlation, but does not necessarily establish causation. One theory of how the two are connected is via insulin.
Insulin, Sugar, and Cancer
Insulin is the gatekeeper for glucose: it allows glucose to get inside the cells where it can be utilized for energy or for storage. When glucose gets used, your cells produce ATP (your body’s energy currency). When glucose gets stored, it gets stored as triglycerides (fat).
Without adequate insulin, glucose can’t get into the cells. This leads to blood vessel damage, cardiovascular disease, kidney disease, etc. Too much insulin, on the other hand, means insulin resistance: your cells become desensitized to its signal. This too means too much glucose in the bloodstream and not enough in the cells, rendering you susceptible to the same complications. Insulin resistance leads to spikes in another hormone called IGF-1, responsible for growth of tissues. Cancer is also a tissue; therefore, there is some increased risk of certain cancers with elevated IGF-1.
High levels of insulin (and glucose) can drive new cancer formation, and they also hinder treatment of existing cancers as well.
Obesity and Cancer
High sugar intake usually leads to obesity, since stored glucose turns into triglycerides (adipose tissue, or fat), as mentioned above. Adipose is not inert, though: it’s active endocrine tissue, and it contributes to inflammation by secreting adipokines, a kind of cytokine (inflammatory second messenger) specific to adipose tissue. Inflammation is of course linked to cancer, and adipokines specifically encourage cancer growth and metastasis.
So losing weight will decrease risk of developing cancer as well. And one of the best ways to lose weight? Cut the sugar.
One of the most important things you can do for cancer prevention is to choose a low sugar, low white carbohydrate, whole food-based diet.
If glucose levels tend to be higher than ideal, intermittent fasting is a great way to help improve insulin sensitivity as well.