Eating a specific type of sugar can turbocharge cancers and make them more deadly, according to new research.
Fructose — which is added to thousands of US food and drinks — was found to speed up the growth of certain kinds of skin, breast and cervical tumors.
The study showed this type of sugar gets converted by the liver into components that tumors need to build new cells and grow.
The more quickly a tumor grows, the more aggressive the cancer may become – able to take over a person’s body before they can fight back.
Added fructose is sugar that is extracted from sources like corn and added to processed foods, most commonly in the form of high fructose corn syrup.
Some early studies have suggested that eating more of these processed sugars might not just accelerate cancer growth, but could also be a cause of some kinds of cancer.
Added fructose is different from fruit fructose, a natural sugar found in fruits that is typically accompanied by fiber and other nutrients that slow down its absorption into the blood.
In the US, manufacturers are generally allowed to add fructose to foods without limitation, which means its found in high amounts in many different processed foods.
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Similarly developed nations have issued caps on the additive — the EU only permits a fraction of the sugar in its processed foods.
This creates a food system in the US where fructose, and high fructose corn syrup, is found in sweetened items, like soda, fruit juice and yogurt, as well in unexpected items, like pasta sauce, salad dressing.
Study author Gary Patti, a professor of chemistry, genetics and medicine at Washington University in St Louis said: 'One take-home message from this current study is that if you are unfortunate enough to have cancer, then you probably want to think about avoiding fructose. Sadly, that is easier said than done.'
That's because there is fructose added to many of the foods that Americans reach for every day.
The average American consumes about 17 teaspoons of added sugar per day - which is more than double the amount that the American Heart Association recommends.
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According to WashU, it's the favored sweetener of many manufacturers because it's sweeter than other options, like glucose.
Dr Patti said that it's found in 'almost everything', meaning that 'unless you actively seek to avoid it, it’s probably part of your diet.'
Because this form of sugar has become so common in American diets, the researchers decided to look into its effects on cancer, as older studies had found that other kinds of sugar could be used to fuel cancer.
Their study looked specifically at breast and cervical cancer, as well as melanoma.
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Cervical cancer and melanoma are less common, affecting approximately 11,500 and 100,640 Americans annually.
The research, published in the journal Nature, used mice and fish with cancer and tumors grown in a petri dish to figure out how cancer might use fructose.
'We were surprised to see that it had a rather dramatic impact. In some cases, the growth rate of the tumors accelerated by two-fold or even higher, Patti said, adding: 'Eating a lot of fructose was clearly very bad for the progression of these tumors.'
First, they fed food with fructose in it to animals with tumors.
They saw that though their overall weight stayed steady, their tumor size began swelling.
They then looked to the tumors grown in the lab, assuming that giving the cells sugar would cause them to grow.
But when the tumors were given fructose, they grew at the same slow rate that they would've had their been no sugar in the dish at all.
So Dr Patti and his team realized that there had to be a middle man.
This graph shows that the total amount of sugar supplied to food and drink manufacturers over time has been increasing, nearing 1970s levels. Millions of Americans still consume about 300 percent the recommended amount of sugar
Returning to animal studies, they used a complex technique called metabolomics, which allows researchers to track chemicals, drugs or nutrients as the move around the body, they traced the path of fructose.
Dr Patti said: 'When we think about tumors, we tend to focus on what dietary components they consume directly. You put something in your body, and then you imagine that the tumor takes it up.'
'But humans are complex. What you put in your body can be consumed by healthy tissue and then converted into something else that tumors use.'
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It turns out that the fructose gets turned into fats in the liver that are key components in building new cells. Each time the cancer builds a new cell, the tumor grows, becoming larger, or becoming able to spread around the body.
This can make it more deadly.
Though the researchers said that more research is needed to link the two for certain, Dr Patti said cancer patients should consider avoiding fructose, when they can.
Dr Patti and his team hope that understanding the way that tumor cells use sugar to build may help them find them better ways to treat cancer in the future.
He said: 'It will be exciting to better understand how dietary fructose influences cancer incidence.'