As someone who works in a hospital with a relatively high percentage of cancer patients, I’m asked multiple times per week whether sugar causes cancer to grow and spread more quickly. This wasn’t something I’d heard in school or during the cancer rotation of my internship, so naturally I was curious about this concept.
Turns out that there’s a reason I didn’t hear about it during school or my internship—it’s a myth that has yet to be supported by research.
So, spoiler alert: Sugar does not “feed” cancer. But, the more honest answer is that it’s complicated. Much like with other areas of research in the cancer field, there are an abundance of unknowns, some potential answers, and a slew of hypothesized contributing factors.
The “sugar myth” likely originates from PET (positron emission tomography) scans, which use an injected radioactive glucose-containing tracer. Metabolically active tissue absorbs the tracer, and the more metabolically active the tissue, the more of the tracer it will absorb. Cancerous tissue tends to be more active than other healthy tissues, and thus it absorbed more of the tracer and, lo and behold, the sugar myth was born.
The reality is that every one of our cells depend on glucose as an energy source to keep cranking along. Different types of cells require varying levels of energy. For example, the cells that make up the tissue of the heart, lungs, and liver use more energy (a.k.a. are more metabolically active) than fat cells. Even if a person eats little to no carbohydrate-containing foods, the body has ways to break down protein (this goes first) and then fat to get at the glucose within each of those molecules.
Unfortunately, cancer cells are major energy suckers and so will use up any energy source that can be broken down into glucose (hint, they all can be) quicker than some of the other healthy cells. Often, cancer patients are receiving chemotherapy, radiation treatments, and/or invasive surgeries to fight the cancer, none of which are conducive to a robust appetite. Patients with cancer are often referred to as being in a “catabolic state,” because if the person doesn’t take in enough calories, they will lose weight and muscle mass at an alarmingly rapid rate.
Therefore, if someone with cancer is attempting to cut out sugar-containing foods, then that person is eliminating a source of calories, and making it that much more difficult to maintain their weight. People who are able to roughly maintain their weight during cancer treatment will endure the grueling process better, have lower risk of infection, and then rebound quicker afterwards.
What about sugar intake for those of us who are currently healthy? Sugar, as a single factor, is not going to cause cancer. But, foods with a high sugar content tend to be higher in calories, and being overweight and inactive are highly correlated with cancer development. Also, in general, sugary foods tend to be lower in beneficial nutrients, like those found in plant foods, such as antioxidants and phytochemicals which help fight malevolent cells.
All of this to say, the myth that sugar perpetuates cancer growth is simply that, a myth. People with cancer need to get calories and protein in any form they possibly can. Period. And for the rest of us, the same mantra of eating healthy and being physically active applies.
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