Carbohydrates, fat and protein are the three principal types of nutrients used as a source of energy for the body.  So why are carbs under suspicion for possibly increasing your cancer risks? It helps to understand how the body breaks down and uses this type of fuel.

Carbohydrates come in simple forms such as sugars, and in complex forms such as starches and fiber. The body breaks down most sugars and starches into glucose, a simple sugar that the body can use to feed its cells. Glucose and the role carbohydrates may play in cancer development have long  drawn research attention due to the "Warburg effect," the observation that tumors have a unique metabolism that requires them to have high amounts of glucose to survive and reproduce.

In theory, higher carbohydrate intake could provide the glucose necessary to support the unique metabolism of cancer cells. Higher carbohydrate intake may also stimulate insulin secretion, which not only accelerates glucose uptake by cancer cells, but also stimulates the rapid reproduction of cancer cells.

Higher fat intake, in contrast, could impair metabolism of cancer cells, which cannot use fat as a fuel, and would increase production of a byproduct that appears to interfere with cancer cell metabolism.

“It is important to point out that there is currently very little data from human studies to support a benefit of restricting carbohydrate in diet, and of increasing healthy fats such as olive oil, nuts and avocado, as a means to reduce risk or improve prognosis in cancer,” said Dr. Kathleen M. Egan, senior member of the Cancer Epidemiology Department at Moffitt. “This is an area of active cancer research.”