In this article, researchers found that cells obtained from breast cancer contain over six times as many receptors for insulin as normal breast tissue cells. Since all carbohydrates that contain glucose (which is most everything) increase insulin levels, this might mean that diets high in carbohydrates will trigger increased growth of these cancer cells. We already know that skin cells that make skin tags grow more rapidly in response to elevated insulin levels triggered by a high carbohydrate diet. It is reasonable to consider that other cells might too.
Imagine one cell out of a million developing the genetic changes to become a cancer cell. If that cell is fed MiracleGro sugar, its chances of becoming a life threatening tumor are much higher than if it was starved of food. The only macronutrient not necessary to be consumed for human survival is carbohydrates. Why should we base our dietary schema on a substance that isn’t necessary for life and can cause early death?