A group of scientists at Weill Cornell Medicine in New York recently published a study in the journal Science that could eventually explain why colon cancer in young adults is on the rise in many western societies.

Colon cancers grew faster in mice

More and more scientific studies show that excess sugar is not good for our health. Recently, another such study has shown that corn sirup, which is a mixture of fructose and glucose, have detrimental effects on the growth of colon cancer – at least in mice. Although, it is still unclear whether human colon cancers would react the same way, the results could be a possible explanation for the recent rise of colon cancer in younger people, according to the researchers.

Genetically-prone people could have a higher risk

Joshua Rabinowitz, a biochemist at Princeton University, who was not directly involved in the study, explained, that especially people who are genetically-prone to developing colon cancer, and thus have a higher risk, should be aware. Although, the corn syrup did not initiate colon cancer, it actually did drive the tumour growth in the tumour-prone mice. That means, for people who are genetically susceptible to cancer, one can of sugary soda a day can drive the progression of precancerous entities into a malignant disease.

What is worse, excess fat or sugar?

In the 1980s, Ancel Keys, a Harvard Scientist of Nutrition, published his „Seven-Country-Study“ which was the starting point of the sugar flood which can be seen until today in our foods and on our scales. Because Keys’ data showed a positive correlation between the consumption of saturated fats – which are mainly present in animal foods – and the development of heart diseases, the food industry switched rapidly from fat to sugar as its favourite ingredient.

As, at the same time, the United States subsidies corn which resulted in huge amounts of cheap high-fructose corn syrup that flooded the market, the food industry, which by the way financed Keys’ study, switched immediately from the more expensive table sugar to the much cheaper corn syrup. This change was the rise of sugary drinks.

Sweetened beverages kicked-off obesity

The sales of sweetened beverages skyrocketed shortly afterwards and kicked-off the obesity epidemic which we can see today, not only in the United States but almost globally. Today we know that Keys’ study was a major fraud, and that fat, especially cholesterol, is not to blame for most cardiovascular diseases. Instead, we are more and more realising that the excess sugar in our food is linked to many diseases, ranging from obesity via metabolic syndrome to even some forms of cancer.

Cancer starts with inflammation

The association between obesity and cancer can be explained as follows: A lot of sugary calories, which can be found everywhere from frozen pizza via tomato sauce to even sausages, is mainly responsible for overweight and obesity. Obesity causes chronic inflammation and this is thought to help tumours to grow. Recent statistics see more and more people, especially overweight ones under the age of 50, who are affected from colon cancer. After 2001, there was an average annual increase of 2.1 percent in young onset colorectal cancer compared to a decrease of 2.5 percent yearly for those 50 and older. Rectal cancer cases increased even more rapidly in younger patients at an average annual change of 3.9 percent. The new study could give at least one answer for this unusual scenario.

Looking for link between cancer and corn syrup

The lead author of the study, Lewis Cantley, who is a biochemist at Weill Cornell Medicine in New York, and postdoc Marcus Goncalves and his collaborators were curious to know whether there could be a direct link between corn syrup sweetened drinks and cancer. Therefore, they studied knock-out mice which develop colon cancers much easier because they lack the gene APC. APC is also an important gene in humans because when it is disabled it predisposes people to develop colon cancer.

To test whether corn syrup really has a significant impact on the growth of colon cancer, the researchers divided the colon cancer bearing mice into two groups. One group were fed on a daily base with a watery solution containing as much high-fructose corn syrup as in a can of soda, while the other group of mice only got plain water. After two month, the sugar swillers had larger and more invasive tumours than the control mice who only drank water.

A special enzymes fuels the cancer growth

With a special test, which uses radioactively labelled glucose and fructose, the researcher followed the sugar through the gut of the mice. Surprisinlgy, they found that most of the fructose was not absorbed into the blood stream in the small intestine but went straight to the colon to feed the tumour cells. And the test showed much more interesting facts inside the tumour cells: The fructose was degraded by a special enzyme called fructokinase (KHK or Ketohexokinase), which lowered the cells energy level and triggered more glucose metabolism to restore it. This glycolysis also produced the urgently needed fats for the tumour cells to grow.

Next, the scientist knocked-out the gene for the KHK enzyme, in addition to the APC gene, in mice. The effect was staggering, because the tumours in the differently fed mice stood the same, there was no difference in the growth rate. These results, the researchers concluded, suggest that beverages sweetened with high-fructose corn syrup – but also with table sugar (which also is a mixture of fructose and glucose) – could probably speed up the transition from precancerous polyps into colon cancers in humans as well.

Sensitive people could be on risk

Jihye Yun who was part of the study team and is now assistant professor at Baylor College of Medicine in Houston, Texas, thinks that even a modest amount of sugary drinks could shorten the time that cancer takes to develop in sensitive people.

Not yet that convinced seems the Swiss physiologist Luc Tappy who works at the University of Lausanne, Switzerland. Although, he states, the experiments were well done and the results in mice are convincing, it needs to be verified whether they are relevant to people as well.

Cantley and his team hopes to answer that question in a future study. The researchers are interested in the question whether a low-sugar diet has the ability to slow down the growth of intestinal polyps in people who are genetically predisposed to develop them. Furthermore, Cantley suggests KHK-inhibiting drugs, which are currently tested in trials for fatty liver disease, could be added to the cancer therapies of people with colon cancer in a clinical trial. Whether inhibiting the KHK enzyme could be really an innovative new therapy option for colon cancer patients has certainly first to be shown in further studies, but it looks promising.

Conclusion:

To be clear, sugar as well as fat are essential nutrients which are needed by our bodies to stay healthy and alive. Neither sugar nor fat of any kind are harmful to our bodies, provided they are not eaten in excess. Unfortunately, our modern convenient food contains way too much sugar. Especially fructose, which can only be metabolised in the liver, makes us thick and sick. Thus, the mantra of the food industry that „a calorie is a calorie“ is not true. Calories from fructose are differently metabolised than from glucose, and that makes a very big difference.

Sources:
https://news.weill.cornell.edu/news/2019/03/high-fructose-corn-syrup-promotes-colon-tumor-growth-in-mice

http://science.sciencemag.org/content/363/6433/1345