When it comes to the rising rates of obesity, sugar is deemed a key culprit. But high sugar intake may not only lead to weight gain; a new study claims it can increase the risk of breast cancer and hasten spread of the disease to the lungs.

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The new study suggests high sugar intake may raise the risk of breast cancer and metastasis.

Study coauthor Peiying Yang, PhD, assistant professor of palliative, rehabilitation and integrative medicine at the University of Texas MD Anderson Cancer Center, and colleagues publish their findings in the journal Cancer Research.

According to the team, previous research has identified a link between dietary sugar intake and risk of breast cancer, with some studies suggesting inflammation may play an important role.

However, Yang notes that no studies had investigated the direct impact of sugar intake on breast cancer development in animal models or looked at the underlying mechanisms of the association in such models.

With this in mind, the team set out to assess how sugar intake influenced breast cancer development in mice that were randomized to various diets, including a sucrose-enriched diet, a fructose-enriched diet and a starch-control diet.

According to the researchers, the amount of sucrose and fructose the mice consumed was comparable to that found in a typical Western diet - characterized by high intake of refined sugars, saturated fat and red meat, and low intake of fresh fruits and vegetables and whole grains.

50-58% of mice fed sucrose-enriched diet developed breast cancer

Compared with mice fed the starch-control diet, those fed the sucrose- and fructose-enriched diets were more likely to develop breast cancer.

At the age of 6 months, for example, the team found 30% of the mice fed the starch-control diet had breast cancer tumors, compared with 50-58% fed the sucrose-enriched diet.

Fast facts about sugar
  • Almost half of Americans' sugar intake comes from soda and fruit drinks
  • A can of Coca-Cola contains around 8.25 tsps of sugar
  • The World Health Organization (WHO) recommend that added sugars should make up less than 10% of daily calories, though less than 5% would provide further benefits.

How much sugar is in your food?

What is more, the researchers found that the mice fed a sucrose- or fructose-enriched diet had significantly more tumors on the lungs than those fed the starch-control diet, suggesting high sugar intake speeds up breast cancer metastasis.

The team found that dietary fructose and sucrose - a combination of glucose and fructose - increased 12-lipoxygenase (12-LOX) signaling, which increased production of 12-hydroxy-5Z,8Z,10E,14Z-eicosatetraenoic acid (12-HETE) to raise risk of breast cancer development and metastasis.

"We determined that it was specifically fructose, in table sugar and high-fructose corn syrup, ubiquitous within our food system, which was responsible for facilitating lung metastasis and 12-HETE production in breast tumors," notes study coauthor Lorenzo Cohen, a professor of palliative, rehabilitation and integrative medicine at the MD Anderson Cancer Center.

"This study suggests that dietary sucrose or fructose induced 12-LOX and 12-HETE production in breast tumor cells in vivo," he adds. "This indicates a possible signaling pathway responsible for sugar-promoted tumor growth in mice. How dietary sucrose and fructose induces 12-HETE and whether it has a direct or indirect effect remains in question."

The researchers note that pinpointing risk factors for breast cancer is a "public health priority," and their study provides further evidence that dietary sugar intake plays a role in breast cancer development.

The finding is particularly important, given the rising sugar consumption in the US; the researchers note that the per capita sugar consumption in the US has reached more than 100 Ibs annually - the equivalent to around 30 tsps of sugar a day.

Given the possible health implications of high sugar intake, a spotlight story from Medical News Today last year investigated whether we should eliminate sugar from out diet.