You may have heard that “sugar feeds cancer.” This is a very oversimplified and potentially dangerous explanation for very complex changes that can happen to carbohydrate metabolism in people with cancer. Glucose is the main energy source for tumors, just as it’s the main source of energy for healthy cells.
The tumor will get the glucose it needs even at the expense of healthy cells. So, even if you avoid all carbohydrates and refined sugars, your liver will convert the amino acids from the protein you eat into sugar or, worse, obtain it by breaking down your muscles.
In addition, avoiding sugar from fruits, dairy products, and other wholesome foods may lead to malnutrition. Therefore, it’s better to reduce your intake of refined sugars, because these don’t add any nutrient density to your diet.
There is an exception to this rule, however: If you’re losing weight because of a poor appetite or symptoms from your cancer or cancer treatment, you need to eat anything that sounds good to you and that you can tolerate.
Your body can break down your muscle to free up amino acids to make sugar, so you’re better off eating a little refined sugar during these times than forcing your body to break down your muscles to obtain it.
That said, some studies suggest that having increased amounts of insulin circulating in the body may promote tumor growth. Insulin is an anabolic hormone that controls blood glucose levels.
Because ingestion of refined sugars can cause an increased amount of insulin to be released from the pancreas to metabolize the sugar, avoiding these foods may be preferable. You can also consider pairing sweet with a little protein or fiber, like a few nuts or some fresh fruit, which may lower the insulin response.