High levels of sugar in the blood spark a biochemical cascade that can lead directly to cancer, according to a study conducted by researchers from the Universidad Rey Juan Carlos in Madrid and published in the journal Molecular Cell.
The research may help explain the long-known connection between poor diet and increased cancer risk.
While sugars are necessary for many bodily functions, a healthy person's blood sugar levels remain within a relatively narrow range due to the hormones glucagon and insulin. When blood sugar levels are slightly too high, a person is diagnosed as prediabetic. When blood sugar levels climb even higher, a person is considered diabetic.
Both prediabetes and diabetes are significantly more common in overweight and obese people; indeed, Type II diabetes is actually caused by many of the same factors as obesity. Researchers have long known that diabetics and obese people have a much higher cancer risk, but the reasons for this have remained unclear.
"Previously we were unsure about how increased blood sugar found in diabetes and obesity could increase cancer risk," said Colin Goding of Oxford University, who was not involved in the study. "This study ... opens the way for potential novel therapies aimed at reducing cancer risk in the obese and diabetic populations."
The new findings came from a study examining how intestinal cells react to sugars by releasing GIP, a hormone that signals the pancreas to release insulin. The researchers found that a protein called s-catenin plays a critical role in intestinal cells' ability to release GIP, and that s-catenin becomes more active in the presence of too much sugar.
Significantly, prior research has shown that s-catenin can also interfere with the natural life cycles of cells, causing them to become immortal and thereby precancerous. Further tests by the researchers confirmed that in the presence of high sugar levels, cells begin to accumulate s-catenin in their nuclei, leading directly to the cell proliferation associated with cancerous tumors.
Why a healthy diet is so important
"We were surprised to realize that changes in our metabolism caused by dietary sugar impact on our cancer risk," lead researcher Custodia Garcia Jimenez said. "We are now investigating what other dietary components may influence our cancer risk. Changing diet is one of easiest prevention strategies that can potentially save a lot of suffering and money."
63 percent of deaths worldwide are now caused by noncommunicable diseases, many of which - such as cancer, diabetes and cardiovascular disease - are strongly linked to lifestyle factors. Health experts estimate that about one in three cancers could be prevented by improved diet and exercise habits.
But globally, both obesity and diabetes are on the rise. According to the World Health Organization, one in 10 adults around the world are now obese, and global obesity rates are doubling every 20 years. One in 10 adults are also diabetic, and the disease was responsible for 4.6 million deaths in 2011. In the United States, diabetes kills more than two people every hour.
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