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.

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.

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), 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!

Mediterranean diet cuts postmenopausal breast cancer risk

Further evidence of the Mediterranean diet's anti-cancer effects has emerged, 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 or 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 processed meat and factory foods rich in sugar, bleached flour and refined 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's authors, most younger women who develop breast cancer 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 even depression.

A vast body of research dating 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.

Strawberries: not just good, but good for you!

Summertime is strawberry time, and I am enjoying it to the full. For I have discovered that the best strawberries don’t come from the supermarket, but from a local farm not three miles from my home.

In the past, strawberry season was an exercise in frustration. Keen to avoid the early berries from Spain (grown in hothouses, tended by underpaid African migrant laborers, sprayed with pesticides and harvested before maturity) I would wait impatiently for the local berries to appear on the supermarket shelves.

However, the season being short and hostage to the vagaries of the local weather, the long-awaited berries rarely made it to my supermarket, or only briefly and at exhorbitant prices. Before I knew it, strawberry season was over and my plans for a freezer full of pureed strawberries had to be shelved until the following year.

A few weeks ago, as I was selecting beautifully fragrant strawberries at the local farmers’ market, the enterprising young grower selling them told me I could come and pick them myself – at half the price he was charging at the market! My family and I went for a short drive to the strawberry farm and as we got out of our car, a beauteous scene unfolded before our eyes: row after row of ruby-red, ripe strawberries glistening in the afternoon sun.

We were handed two wooden crates and set about filling them in the company of the friendly farm dog. Within ½ hour we had picked 8 kilograms of sweet, aromatic mara des bois strawberries, probably the most fragrant of all strawberry varieties, with a flavor resembling the sweet, spicy miniature forest berries you sometimes discover on particularly successful country walks. (They remind us why the Italian name for strawberry is fragola – essentially meaning ‘fragrant.’)

Best of all, the berries had not been treated with any chemicals; to rein in the weeds, the farmer had covered much of his field with black plastic sheeting into which he had cut holes for the strawberry bushes to grow through.

Strawberries are the very incarnation of nutrient-dense food: low in calories (1 cup only contains 43 calories) and brimming with nutrients. Eating just 10 medium-sized strawberries (1 cup or 140 grams) gives you 82 mg of vitamin C – or 136% of the recommended daily average! Strawberries are also rich sources of fiber, potassium, manganese and folic acid.

Strawberries (and other berries, such as raspberries, blueberries, cranberries and blackberries) are also one of our staunchest allies for dietary cancer prevention. A large body of research has established the anti-cancer potential of berry fruit phytochemicals. These include anthocyanins (pigments that impart the attractive colors to berry fruits and colorful vegetables), quercetin (a compound also found in onions, apple skins and tea), proanthocyanidins (common to green tea, grape skin and seeds, blueberries, cranberries, dark chocolate, etc.), tannins (particularly ellagitannins, found in strawberries, black raspberries, red raspberries, blackberries, muscadine grapes, some nuts and oak-aged beverages) and other plant chemicals.

Their cancer-protective effects are multiple: berries contain powerful antioxidants (notably ellagic acid, particularly prevalent in strawberries and raspberries) that protect our cells from free-radical attacks which can lead to cancerous changes. Berry compounds have been shown in laboratory experiments to inhibit cancer cell proliferation and to promote the detoxification of carcinogens. They can even induce apoptosis (cell death when a cell is no longer needed) and reinforce the cancer-destroying effects of certain chemotherapy drugs.

Interestingly, organically grown strawberries appear to have stronger anti-cancer effects than conventionally grown ones. Swedish scientists recently found that extracts of organic strawberries contained higher levels of vitamin C and phenolic compounds than their conventional cousins. Tested on human colon cancer and breast cancer cells, both types of strawberry extract reduced cell growth, but the organically grown ones were more effective at inhibiting proliferation than the conventionally grown ones.

If you can’t obtain organically grown strawberries but have a garden (even a small one will do), strawberries are easy to grow, even for beginners, and are very rewarding. Not only can they carry up to three flushes of fruit throughout the summer, but they are also perennial, meaning that they flower and carry fruit every year, year after year.

So let’s enjoy strawberries while the season lasts! Most often I eat them as they come off the bush, or perhaps cut into creamy ewes’ milk yogurt along with a finely chopped mint leaf and a smidgen of acacia honey. Strawberries elevate any morning smoothie to a feast (I usually add banana and a spoonful of almond butter to make it more filling), as well as lending a lovely burst of color and freshness to porridge or muesli in the morning. To make the season last a little longer, I also puree them and freeze them in ice-cube trays or containers, to enjoy when fresh strawberries have become a distant dream.

To ring in the changes, I recently came up with a savory strawberry sauce that’s delicious with chicken or duck; if you would like to try it, I have posted it on my website.