Sugar and cancer: A surprise connection or 50-year cover-up?

Can sugar cause cancer? It seems that evidence pointing this way was discovered in a study funded by the sugar industry nearly 50 years ago—but the work was never published.

An industry-funded research project found higher levels of a cancer-causing enzyme in rats fed a diet high in table sugar.

Most of us—me included—are partial to the occasional sweet treat. But we all know that large amounts of sugar aren’t good for our health. In fact, there are plenty of studies showing links between sugar and diabetes, heart disease, and even mental health.

Cancer only entered the mix relatively recently. Last year, Medical News Today reported on a study that showed that over half of mice fed a sucrose-rich diet developed breast cancer.

However, an article published this week in the journal PLOS Biology cites internal documents by the Sugar Research Foundation (SRF), suggesting that knowledge of a possible link between sugar and cancer goes back as far as the 1960s.

Was it a cover-up? And what evidence is there to say that the odd donut might leave me with cancer?

Sugar and the microbiome: ‘Project 259’

Back in the 1960s, the debate was all about heart disease. Who is the culprit: sugar or fat?

A 1967 review article in The New England Journal of Medicine concluded that dietary fats were to blame. What wasn’t clear at the time, though, was that the authors received funding from the SRF equivalent to roughly $50,000 in today’s money to publish their review.

Disclosure of conflict of interest wasn’t mandatory until the 1980s, so technically, this wasn’t wrong. But what it did do was set the scene for more clandestine research to follow.

The review revealed that rats fed a high-sucrose diet had higher serum cholesterol levels than those on a starch-based diet. The authors speculated that gut bacteria were to blame.

And so ‘Project 259’ was born in 1968. This was a study to compare “the nutritional effects of [bacterial] organisms in the intestinal tract” in rats fed sucrose versus those fed starch.

A substantial funding grant—the equivalent of $187,583 in today’s money—went to W.F.R. Pover, from the Department of Clinical Biochemistry at the University of Birmingham in the United Kingdom, to get to the bottom of this phenomenon.

Stanton A. Glantz is the senior author of the paper published in the journal PLOS Biology and a professor at the University of California, San Francisco.

He cites an SRF internal report, which explains that “[a]mong [Project 259’s] observations was […] that the urine from rats on the basic diet contained an inhibitor of beta-glucuronidase activity in a quantity greater than that from sucrose-fed animals. This is one of the first demonstrations of a biological difference between sucrose and starch-fed rats.”

So, there was a difference. But what does this have to do with cancer?

Beta-glucuronidase and cancer

Beta-glucuronidase is an enzyme that helps to break down large molecules. It also plays a role in cancer. At the time of Project 259, a link between beta-glucuronidase and bladder cancer had already been implied.

Of course, Pover’s findings were only preliminary, and he was running behind schedule to finish his work. When he asked for a 3-month extension to conclude his experiments, the SRF—which had, by now, become the International Sugar Research Foundation (ISRF)—stopped the funding.

“Based on ISRF’s interpretation of preliminary results,” explains Professor Glantz in the paper, “extending Project 259’s funding would have been unfavorable to the sugar industry’s commercial interests.”

“In addition,” he goes on to say, “publication of results suggesting an association between sucrose consumption and bladder cancer would likely have had further adverse regulatory implications to the sugar industry.”

He suggests that the FDA may have taken a close look at sucrose and its possible link to cancer.

“Had ISRF disclosed Project 259’s findings, it is likely that sucrose would have received scrutiny as a potential carcinogen.”

Professor Stanton Glantz

In a press release, the Sugar Association—a United States trade association—explain their own viewpoint on why the study wasn’t funded to completion. “[T]he study was significantly delayed; it was consequently over budget; and the delay overlapped with an organizational restructuring […].”

Whether the ISRF withheld the results of the study on purpose is hard to say with certainty. Yet the evidence supporting a link between sugar and cancer is mounting.

Sucrose and cancer today

Sugar and sugar-sweetened foods and drinks have been increasingly scrutinized for their role in promoting cancer development and cancer spread.

In an editorial in Nutrition, Dr. Undurti N. Das highlighted the fact that fructose, a constituent of table sugar, or sucrose, changes cell metabolism and raises the activity of cancer-promoting proteins.

In an accompanying article, Ashutosh Kumar, PhD, and his colleagues—from the Department of Pharmacology and Toxicology at the National Institute of Pharmaceutical Education and Research in Hyderabad in India—echo this sentiment.

But Kumar also highlights that “[t]here are many published reports with conflicting results regarding the role of carbohydrates (mainly fructose) and cancer prevalence.”

For instance, several studies have found an increased risk of endometrial cancer in women who consumed high levels of sucrose, yet when it comes to other types of cancer, the data are less clear.

While some studies have linked sugar intake to colon cancer—particularly in men—a 2014 study failed to find a clear-cut association.

As mentioned earlier, we have previously reported on a study that revealed that sucrose increases breast cancer rates. Over half of mice fed a sucrose-rich diet developed breast cancer, while only 30% of mice that consumed a starch-based diet did. While a number of population studies concur with this finding, others refute such a link.

Whether and how sugar contributes to the many different types of cancer that are plaguing the human race is not entirely clear at this point. Perhaps we should all be cutting down our sugar consumption.

The question is, how easy is it to get away from the sweet temptation that is sugar?

Sugar lurks everywhere

It makes sense that food and drinks that taste sweet contain sugar. However, hidden sugars are increasingly being unearthed in a plethora of foods—there is no getting away from the stuff.

To my own surprise, I found that sugar was listed as one of the ingredients in a jar of roasted bell peppers in the grocery store last week. Luckily, few things pass my scrutinizing eyes, otherwise my supposedly healthful salad may have been anything but.

For more information on the what lurks in our food, check out our article on “Added sugar: What you need to know.” I was particularly surprised to read that sugar makes its way into our food hidden as fruit juice concentrates.

So, what does it all mean? There is clearly plenty of evidence that too much sugar is bad for our health. Whether we can rely on industry-funded research to get to the bottom of this is a contentious issue and is perhaps best left to personal choice.

A healthful diet is one of the key ingredients to personal health, and there are countless studies supporting this claim. Taking a measured look at the amount of sugar that we put into our bodies, whether consciously or hidden in plain sight by the food industry, is certainly not going to do us any harm. If anything, it’s going to sweeten up our health.

—Yella Hewings-Martin, PhD

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