Sugar and cancer: results of a 9-year study
Sugar has long been known to have an involvement in the onset and progression of cancer, but the specific mechanisms behind this relationship have always been hard to pinpoint. A recently published nine-year-long study has offered new insight into the role sugar has to play in the metabolism of cancer cells.
Cancer cells are addicted to glucose
Most of the cells in the body get their energy from an efficient process called aerobic respiration, which requires oxygen. Cancer cells, however, tend to use a process called glycolysis, which is much less efficient at producing energy. This means cancer cells need to take in and use much more glucose to produce the same amount of energy as normal cells.
Cancer cells have been known to be addicted to glucose for a very long time. In fact, Otto Warburg first described this phenomenon, which became known as the Warburg effect, in 1924.
More recent evidence has suggested that the wastage of sugar by cancer cells allows them to rapidly accumulate the building blocks required to produce new cells: lipids (fats), amino acids (for protein) and nucleic acids (for DNA). Producing lots of these is thought to enable cancer cells to grow and divide much quicker than normal cells.
The most recent breakthrough in the area has come from a group of scientists in Belgium, who have culminated nine years of research to deduce how sugar contributes to the growth and aggression of cancer cells. Their study is published in Nature Communications.
The group showed that Ras, a protein that controls cell growth and is highly active in cancer, is activated by high glucose usage. This activation of Ras allows cancer cells to grow and divide at an increased rate. This finding suggests that cancer’s addiction to sugar is not just a symptom, but also a cause of tumour aggressiveness.
The metabolism (breakdown) of sugar was linked to activation of Ras through the formation of a compound called fructose-1,6-bisphosphate. The researchers used yeast cells to carry out experiments and proved this mechanism’s presence in mammal cells too.
So what do the results of this study mean? Professor Johan Thevelein, the head author of the study, spoke from Belgium’s VIB-KU Leuven Center for Cancer Biology in a statement:
“Our research reveals how the hyperactive sugar consumption of cancerous cells leads to a vicious cycle of continued stimulation of cancer development and growth. Thus, it is able to explain the correlation between the strength of the Warburg effect and tumour aggressiveness. This link between sugar and cancer has sweeping consequences. Our results provide a foundation for future research in this domain, which can now be performed with a much more precise and relevant focus.”
While these findings do not prove that sugar directly causes cancer, they show how overuse of sugar by the body’s cells can contribute to the onset and progression of cancer. Indeed, obesity and type 2 diabetes are estimated to be responsible for 800,000 cases of cancer per year.
Can cancer’s sugar supply be cut off?
Often, identifying a mechanism by which a disease progresses allows treatments to be formulated. No doubt, there will be efforts to develop drugs to target this mechanism in cancer. But besides this, is there anything we can do off our own back?
Getting more of our energy from fat rather than carbohydrate may be helpful. Production of fructose-1,6-bisphosphate, and flow of glycolysis in general, is increased by the action of insulin. Under normal conditions, this helps us make use of the energy from the glucose in our diet. However, high insulin levels could play to cancer’s advantage, as we now know that high rates of glycolysis enable cancer cells to grow and divide more rapidly. Additionally, the hormone glucagon, whose actions run counter to insulin’s, reduces glycolysis and production of fructose-1,6-bisphosphate. By this logic then, a low carb, high fat diet lowers insulin levels while increasing the action of glucagon, thus acting to reduce glycolysis.
Very low carb, ketogenic diets are beginning to show promise as a cancer therapy alongside radiotherapy and chemotherapy. Carbohydrate restriction seems to make cancer cells more susceptible to treatment, whilst protecting healthy cells, and changes to insulin are thought to be involved. More clinical trials are underway, looking at brain cancers in particular.
In the long term, eating a low carb diet that reduces the body’s use of sugar is likely to reduce the risk of certain cancers. This area of research is relatively new, and is ongoing, but the potential for carbohydrate restriction, particularly sugar restriction, in cancer prevention is certainly worth thinking about.