All kinds of cells, including cancer cells, depend on blood sugar (glucose) for energy. But giving more sugar to cancer cells doesn’t make them grow faster. Likewise, depriving cancer cells of sugar doesn’t make them grow more slowly.
This misconception may be based in part on a misunderstanding of positron emission tomography (PET) scans, which use a small amount of radioactive tracer — typically a form of glucose. All tissues in your body absorb some of this tracer, but tissues that are using more energy — including cancer cells — absorb greater amounts. For this reason, some people have concluded that cancer cells grow faster on sugar. But this isn’t true.