Carbs and Pancreatic Cancer: Why “Null Findings” Matter

Say you’re a researcher. You’ve spent months collecting and analyzing data, crunching numbers and composing tables, but it’s all been for naught. That hypothesis you set out to test (say, that a link exists between a specific food and a known indicator of cancer risk) didn’t pan out. In your investigation at least, you found no such link.

You have achieved what in scientific circles is called a “null finding.” And, in a very real sense, that’s not nothing.

Null findings don’t make headlines, and often don’t even get published. (The tendency of journal editors to publish results that seem “new” over those that find no association — or that simply accord with previously published results — is a source of publication bias, which over time can distort the general scientific opinion on a given subject.)

But there is an important difference between a null finding capable of closing the book on a given question — that says, essentially “There’s no there there, move along.” — and a null finding that says simply “We need more and better data before we can make a judgment.”

On those rare occasions when the media do pick up on a null finding, there is a tendency to mistake one kind for another. Let’s take a look at a recent null finding and see what it really has to say.

Carbs and Pancreatic Cancer: No Link?

A new review of the research now suggests that the amount of total carbohydrates consumed does not affect the development of pancreatic cancer.

The study is part of AICR/WCRF’s Continuous Update Project (CUP).

For the analysis, researchers looked at 10 relevant population studies. All studies were prospective, asking participants about their dietary habits and then tracking incidence of pancreatic cancer over time.

The analysis found no link between pancreatic caner risk and total carbohydrates, sucrose, and glycemic index. You can read more here.

This null finding for a link between carbohydrates and cancer risk is not the final word on the subject. The paper’s authors note the small number of studies that exist, the differences in the way these studies classify food and food components, and the fact that most took place in the US, where the diet is relatively homogenous, making it more difficult to pinpoint associations.

In this case, this null finding is a clear signal to researchers that more and better studies are needed.

Coffee and Cancer: No Link!

For decades, the science on coffee and cancer risk pinged back and forth. Some 1960s animal studies threw suspicion on caffeine as a possible cause of certain cancers. Throughout the 1970s and 80s, some research suggested that the popular beverage increased risk of bladder and pancreatic cancers.

As researchers continued to study coffee’s health effects using more rigorous methods and with larger groups of people, those links reported in earlier studies failed to turn up.

AICR/WCRF’s 2007 expert report looked at all the collected evidence, and judged that coffee neither increases nor decreases the risk of pancreatic or kidney cancer – the two cancers with enough evidence to make a conclusion.

This null finding is fundamentally different in nature than the null finding in the carbohydrates-pancreatic cancer study above. Here, the evidence is ample, consistent and of high quality.  It’s enough for AICR to urge scientists to focus their precious time, effort and resources on other areas of research that remain under-studied — like the question of carbohydrates, sugar and cancer.


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