Cancer cells love sugar, and they're not fussy

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.

Since fructose makes up a large proportion of western diets (high-fructose corn syrup accounts for more than 40 per cent of caloric sweeteners added to foods and drinks), a research team at UCLA's Jonsson Comprehensive Cancer Center wanted to study its effect on cancer cells.

The researchers added fructose to one set of human pancreatic cancer cells in petri dishes and glucose 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.

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. Indeed, cancer patients would probably be better off avoiding it. 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), commenting 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!

Mediterranean diet may lower breast cancer risk

Further evidence of the Mediterranean diet's anti-cancer effects has just been published, cheering those of us who believe that this style of eating may be one of the best forms of dietary cancer-prevention around.

In a study that appeared recently in the American Journal of Clinical Nutrition, researchers found that among 14,800 Greek women tracked for a decade, those who stuck most closely to the region's traditional diet were less likely to be diagnosed with breast cancer than those who least closely followed Mediterranean eating patterns.

The link was observed only among women who were past menopause: those with the closest adherence to the Mediterranean diet were 22% less likely to develop breast cancer during the study than those who adhered least to this style of eating.

As I wrote here recently, I believe that Mediterranean-style eating is a key component of lifestyle cancer prevention. Best of all, you don't have to live in a Mediterranean country to reap the benefits of the Mediterranean diet: this term simply describes a pattern of eating that is rich in fresh vegetables, fruits, olive oil, fatty fish, nuts, seeds, garlic, herbs and spices and relatively low in dairy and meat.

The wide variety of fresh plant foods that characterizes this diet provides a vast array of cancer-fighting compounds. These are largely absent from modern western diets which comprise a large proportion of highly processed factory foods rich in sugar, refined starches and industrially transformed vegetable oils. These types of ‘foods' are thought to provide a fertile ground for cancer cells to grow and spread.

The Mediterranean diet may be breast-cancer protective in several ways. For one, studies (this one or this one) have found that women who closely follow the diet tend to have lower levels of estrogen, a hormone that fuels the growth of the majority of breast cancers.

Moreover, cell studies conducted in laboratories (this one or this one) indicate that the fats in the Mediterranean diet - olive oil and the omega-3 fats in oily fish - may slow the growth of cancer cells.
The Mediterranean diet is also typically rich in flavonoids (in particular, flavones, flavonoids and resveratrol), substances with important antioxidant properties. Antioxidants protect body cells from free-radical damage that can eventually lead to disease, including cancer.

But why should the Mediterranean diet may offer greater protection to postmenopausal than to premenopausal women? According to the study, most younger women who develop breast cancer tend to have a genetic predisposition to the disease, whereas in older women, lifestyle and environmental factors may be more important contributors to risk.

That's not to say that younger women don't also derive benefits from Mediterranean-style eating. As far as I'm concerned, the earlier we can get healthy eating patterns in place (ideally in childhood!), the better armed we are against illness in later life - and not only cancer, but also cardiovascular disease, obesity, diabetes, fertility problems and depression.

A vast body of research going back to the 1950s suggests that the Mediterranean diet offers substantial protection against all these conditions. And when paired with other healthy lifestyle habits - regular physical activity, adequate rest, not smoking, and avoiding excessive alcohol intake - the protective effects are even greater.