Health

From the Mayo Clinic:

Myth: People who have cancer shouldn't eat sugar, since it can cause cancer to grow faster.
Fact: More research is needed to understand the relationship between sugar in the diet and cancer. 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.

There is some evidence that consuming large amounts of sugar is associated with an increased risk of certain cancers, including esophageal cancer. Eating too much sugar can also lead to weight gain and increase the risk of obesity and diabetes, which may increase the risk of cancer.

https://www.mayoclinic.org/diseases-conditions/cancer/in-depth/cancer-causes/art-20044714#:~:text=Myth%3A%20People%20who%20have%20cancer,sugar%20(glucose)%20for%20energy


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So consuming too much sugar is bad for you in a variety of ways, but it doesn't fuel cancer in those who have it already.