Here's How Sugar Might Fuel the Growth of Cancer

http://www.nbcnews.com/health/cancer/here-s-how-sugar-might-fuel-growth-cancer-n488456

by Maggie Fox
Jan. 1, 2016

Researchers may be able to explain how sugar might fuel the growth of cancer. They say it boils down to one type of sugar in particular: fructose.

Tests in mice show a possible mechanism for how it happens. The findings, published in the journal Cancer Research, support studies that suggest people who consume more sugar have a higher risk of cancer — especially breast cancer.

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The findings add one more piece of evidence to a growing body of science that shows a Western-style diet is a major risk factor for many types of cancer. Other research has shown that at least two-thirds of all cases of cancer come down to lifestyle choices — tobacco use, an unhealthy diet and a lack of exercise.

Research has also pointed to refined sugar as one of the culprits. But this factor is harder to pin down, since "sugar" is a very broadly used term. Some sugars are vital nutrients, and the body uses a form of sugar called glucose to generate energy.

Cohen's team found that fructose, in particular, affects a metabolic process (or pathway) called 12-LOX. It helps cells metastasize, or spread.

"The majority of cancer patients don't die of their primary tumor. They die of metastatic disease," Cohen told NBC News.

These findings help explain what other researchers have seen looking at cancer patients in general: Those who eat more sugary foods are more likely to have advanced cancer.

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A human study reported that dietary sucrose/fructose/glucose but not starch is associated with increased risk of breast cancer," they wrote in their report.

When the mice were six months old, 30 percent of those fed a starch-dominant diet had breast cancer. But half the mice that had been fed extra sucrose had breast tumors. And the more sugar they were fed, the bigger the tumors grew.

Sucrose or table sugar is actually composed of two sugars: glucose and fructose. Cohen's team wanted to see if one or the other made a difference, because the body processes them differently.

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They studied where the sugar went in the bodies of the mice. When the mice got more fructose, they grew larger tumors and faster.

This supports other findings that have shown pancreatic tumors also thrive on fructose.

"It seems that fructose is driving this inflammatory process more than glucose," Cohen said. "It seems from these series of experiments that it really fructose that within the sucrose that is the driver of the tumorigenic process."

Any sugar helped make the tumors grow faster, but fructose did it significantly more.

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The implications for people are clear. Cohen notes that fructose consumption in the U.S. surged from about half a pound a person a year in 1970 to more than 62 pounds a year in 1997. That's mainly due to the broad use of high fructose corn syrup.

Other experts and several trade groups representing the food and beverage industry argue that fructose and sugar in general are safe ingredients and say there's really no evidence that fructose is any worse than any other sugars. They point out that fructose is found in natural fruit, for example.

Cohen says that like oxygen, a little is vital for life but too much is toxic.

"We need glucose. We need sugar. It is an energy source and we need it to live," he said. "We refine sugar that extracted from its source and consume in extremely high quantities."

Fruit does provide fructose, but it's mixed with fiber and other nutrients. This study didn't look at whether that affects the growth of tumors, but other experts point out that sweetened soft drinks — the largest single source of sugar in the western diet — provide only sugar and no other nutrients.

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There are other reasons to minimize sugar. Other studies show sugar-heavy diets can fuel heart disease, diabetes and Alzheimer's disease. But cutting sugar can lower blood pressure and blood sugar levels after only a few days.

A study published in June estimated that eating too much sugar killed 184,000 people a year.