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Cancer cells love sugar, and they're not fussy

Fructose and glucose found to fuel pancreatic cancer cell growth

Pancreatic cancer cells use the sugar fructose to help the tumor grow more quickly, researchers have discovered. Published this month in Cancer Research, these findings serve as a powerful reminder that anyone wishing to curb their cancer risk should start by reducing the amount of sugar they eat.

To assess the effect of fructose on cancer cells, UCLA researchers added glucose to one set of human pancreatic cancer cells and fructose to another set of cells. After letting the cells interact with the sugars, both fructose and glucose were found to increase cancer cell growth at similar rates but through different metabolic pathways. This is the first time a link has been shown between fructose and cancer proliferation.

"In this study we show that cancers can use fructose just as readily as glucose to fuel their growth," said Anthony Heaney, the study's lead author. "The modern diet contains a lot of refined sugar including fructose and it's a hidden danger implicated in a lot of modern diseases, such as obesity, diabetes and fatty liver." While this study was done on pancreatic cancer, these findings may not be unique to that cancer type, Heaney said.

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Americans in particular consume large amounts of fructose, mainly in high-fructose corn syrup, a mix of fructose and glucose that is used in soft drinks, bread and a range of other processed foods. High-fructose corn syrup is about 45% glucose and 55% fructose. People also get fructose from sucrose, known as table sugar, which is 50% glucose and 50% fructose.

It has been known for decades that cancer cells thrive on glucose. Moreover, foods that cause a sharp rise in blood glucose (i.e. foods with a high glycemic index (GI) ranking) trigger the secretion of insulin and insulin growth factor (IGF-1), two hormones that also promote cancer growth.

Many health-conscious eaters have therefore shifted to foods with lower GI rankings - an excellent idea if this involves replacing refined, processed starches with natural, whole carbohydrates rich in fiber, protein, fat and micronutrients. However, some people have also switched to fructose-rich sweeteners because these have low GI rankings. Indeed, popular ‘low-carb' weight-loss diets such as the Montignac diet promote the use of pure, crystallized fructose as a sweetener.

More recently, a fashionable sweetener widely touted as a natural and healthy alternative to other sugars has taken the health food community by storm: agave syrup. True, it has a low GI ranking and is ‘natural' to the extent that it is derived from a plant (albeit after intense processing). However, some brands of agave syrup contain as much as 90% fructose.

In the light of the UCLA study, agave syrup may therefore not be helpful for dietary cancer prevention, and cancer patients are probably better off avoiding it altogether. Indeed, "efforts to reduce refined fructose intake or inhibit fructose-mediated actions may disrupt cancer growth," the study states.

According to the American Institute for Cancer Research (AICR), commeting on the study on its blog, "the findings are interesting, but more research is needed before it can be used to make recommendations on public health." This is only one study, they note, and it is a cell study. This means that its findings may not necessarily be replicated in animals or humans.

However, the study does highlight that adding sugar to our diet raises cancer risks. "A healthy diet will always include some sugar, as it naturally occurs in nutritious foods like fruit and milk," the AICR writes. "The key is to limit added sugars of all types, rather than focusing on glucose versus fructose or sucrose."

With obesity in the US continuing to rise, "Americans need to cut back on added sugar, no matter where it comes from. Reducing added sugar will help people get to and maintain a healthy weight, and that is one way research clearly shows that we can prevent pancreatic cancer," says the AICR. The WCRF/AICR in its 2009 policy report found that 28% of pancreatic cancers could be prevented if Americans maintained a healthy weight.

In my next post I'll take a look at practical ways to rein in our desire for sugar. It's not as hard as you think!

Conner Middelmann Whitney is a nutritionist, journalist, chef, and former cancer patient.

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