Around one century ago, Otto Warburg, well-known German physiologist, discovered that cancer cells are addicted to sugar.
Normal cells depend on oxygen for their growth. Cancer cells, however, grow by devouring large amounts of glucose, even in an oxygen-rich environment. This phenomenon occurs in as many as 80 percent of cancers.
The metabolic way cancer cells use sugar as an energy source is called glycolytic metabolism. This phenomenon is known as the Warburg effect.
The metabolism and growth rate of cancer cells are much faster than normal cells, and their consumption of sugar is also faster than we can imagine. It can be said that cancer cells are constantly thirsty for sugar.
In a 2014 paper published in BMC Biology, American scientists showed that many cancer cells specifically choose glucose as their food and consume glucose 50 to 100 times faster than normal tissues.
Cancer cells desperately absorb sugar and consume it rapidly in order to grow, multiply, and spread rapidly.
Sugar can produce carbohydrates, proteins, and fats, which to cells are like bricks, cement, and insulating materials with which to build homes. In addition, sugar also makes DNA and RNA for cells as their genetic blueprints.
Inspired by the Warburg effect, scientists have further developed a new way to diagnose cancer— positron emission tomography (PET).
It works by injecting the patient with a contrast agent (usually fluorinated deoxyglucose) and waiting an hour or so for the fluorinated deoxyglucose to enter the body’s metabolic system, at which point imaging scans are taken. When the glucose is concentrated in a certain area of the body, the image of that area will become brighter.
For example, when a patient is examined for pancreatic cancer, a normal pancreas does not light up on PET scans. However, when parts of the pancreas become brighter, it means that cancer is present.
Cancer is not just one type of disease. It is a series of genetic or metabolic diseases caused by mitochondrial dysfunction of cells. Moreover, the organs or sites where cancer occurs are often places where the metabolism of the organisms is relatively vigorous.
Since cancer cells prefer glycolytic metabolism as their energy source, high consumption of sugar can lead to faster growth and spread of cancer. This explains why there is much epidemiological evidence that people with diabetes are more likely to develop cancer, especially breast, colon, prostate, liver, and pancreatic cancers.
A growing number of studies have found a direct correlation between sugar intake and increased cancer risk.
Researchers in the United States followed 3,184 Americans aged 26 to 84 from 1991 to 2013 and found that higher juice intake increased the risk of prostate cancer by 58 percent and higher sugary drink intake increased the risk of obesity-related cancers by 59 percent in subjects with over-central obesity.
A Swedish epidemiological cohort study of more than 60,000 women discovered that those consuming diets with high dietary glycemic index, high glycemic load and high carbohydrate intake were more likely to develop breast cancer. In addition, women in the group with the highest sugar intake (over 35 g of sucrose per day, plus consumption of sweet bread and cookies more than three times per week) were at significantly increased risk of endometrial cancer.
Several researchers in the United States jointly conducted a systematic evaluation of 37 prospective studies on sugar and cancer risk published in authoritative journals from 1990 to 2017. According to the results, high sugar intake may increase cancer risk by promoting insulin-glucose dysregulation, oxidative stress, inflammation, and obesity. Among them, two studies on added sugars showed that high sugar intake increased the risk of cancer by 60 percent to 95 percent. Out of 15 studies on sugary foods and beverages, eight found that the higher the intake of sugary beverages, the higher the risk of cancer, with an increase of 23 percent to 200 precent.
Furthermore, consuming too much sugar also increases cancer mortality.
In a study published in the journal Clinical Nutrition, researchers followed 7,447 tested individuals over many years to examine the association between sugar intake and cancer incidence, cancer mortality and total mortality. They found that for every 5-gram increase per day in liquid sugar intake, the incidence of cancer increased by 8 percent. Furthermore, simple sugar intake from beverages and fruit juices was associated with increased risk of overall cancer mortality and all-cause mortality.
You may wonder, since cancer cells love sugar, if we cut out carbohydrates and sugar completely, can we starve them to death?
Unfortunately, this is not the right way.
This is because our body’s functions are extremely sophisticated and complex. If we simply cut out sugar and carbohydrates, the body will quickly turn to other substances to maintain metabolism and survival. This is especially true of the cunning cancer cells. And those who have undergone specific cancer treatments need to consume adequate amounts of nutrients, including carbohydrates, to help their bodies recover further.
However, it is possible to block the cancer cells from eating sugar and consuming energy through specific treatments.
Dr. Sophia Lunt, associate professor of biochemistry and molecular biology at Michigan State University, gave a Tedx Talk to introduce the public to a promising new direction in cancer therapy, which is to treat cancer by affecting the metabolism of cancer cells.
By blocking multiple genes involved in cancer cell metabolism, Dr. Lunt has attempted to cut off multiple pathways that support cancer cell growth and metabolism at the same time, to stop the growth of cancer cells. Happily, normal cells could continue to grow during this process.
However, the process is very complicated. During her talk, Dr. Lunt presented the audience with a labyrinth-like picture of the metabolic mechanism of cancer cells. She added that the diagram had already been simplified.
