Does sugar feed cancer? This is one of our most frequently asked questions.
There is no strong evidence that directly links sugar to increased cancer risk, yet there may be an indirect link.
All cells in our body – including cancer cells – need sugar (glucose) from our bloodstream for fuel. We get that blood sugar from foods containing carbohydrates, including vegetables, fruits, whole grains and low-fat dairy sources. Some glucose is produced within our bodies from protein.
A biologic mechanism in yeast cells may explain the relationship between sugar and malignant tumors, according to a recent study. The study begins by looking closely at cancer cells’ appetite for sugar.
Scientists understand that cancer cells support their rapid reproduction by rewiring their metabolisms to take glucose, ferment it and produce lactate.
Conversely, healthy cells continue with normal respiration, a process in which they take glucose and break it down into carbon dioxide and water.
This “switch” of cancer cells from respiration to fermentation is something that was discovered by Otto Warburg, a German biochemist, about 70 or 80 years ago. It is known as “The Warburg effect.”
Fermentation of sugar to lactic acid produces about 15 times less energy than respiration of sugar. Yet cancer cells grow much more rapidly than normal cells, and yeast actually grows the fastest when they ferment.
This raises an important question: Is the Warburg effect a symptom of cancer – or a cause of it?
As sugar is broken down in cells, the intermediate compound activates the RAS proteins, and this in turn stimulates cell proliferation. RAS is a proto-oncogene: a gene that codes for proteins that help to regulate cell growth and differentiation. Proto-oncogenes can become oncogenes or cancer-causing genes when mutations occur. Mutant forms of RAS proteins are present in many tumors. The new study, then, reveals “a vicious cycle”. This cycle seen in yeast cells might help explain the aggressiveness of cancer.
Eating sugar or Obesity?
Even though the researchers pinpointed some similarities between yeast and human cancer cells, the study showed only an increased rate of cell growth triggered by glucose. Even though the team showed RAS pathways being activated, this actually didn’t result in the cells replicating more quickly.
When people are heavier, their bodies manage sugar differently than those of people who are lighter. This sugar management is what leads to type 2 diabetes.
Researchers have known for a while that having a higher blood sugar and having a higher level of insulin in your system are both linked to the risk of developing cancer.
At the same time, studies that have tried to look at how eating sugar might be linked to cancer risk have been much less consistent. Once again, how the body manages sugar — and not the sweetener itself — may be key.
Studies in breast cancer patients have compared low-carbohydrate diets to low-fat diets and found that the amount of weight people lost, not the diet itself, was important. If it led to weight loss, either diet brought an identical lowering of sugar in the blood stream and an identical lowering of insulin.
Translated into practical advice for cancer patients: If you have someone who is obese or overweight, helping them to lose weight is going to be an important thing. We all know that when you eat a lot of sugar, you have a tendency to become more obese. And obesity is linked to a higher risk of cancer.
Though it’s too early to say, it could be possible that when you eat too much sugar over a long time, maybe this can also lead in some way to dysregulation of the RAS protein in the normal cells, and possibly it is this “dysregulation” that triggers RAS genes into becoming mutants.
It’s better not to eat too much sugar so that you don’t become obese. And if at the same time, you also decrease your risk of cancer, the better but this is something one cannot make a statement about at this moment.
If anything, one would suggest that cancer patients, or indeed anyone, eat less simple sugars and more complex sugars, such as those found in starch and whole grains. Complex sugars are released more slowly and are taken up by the body more slowly, and this might be helpful to cancer patients and to avoid obesity in general.