Study: Are Scientists Overstating the Diet-Cancer Link?

A study published in the American Journal of Clinical Nutrition highlights why studying the link between diet and cancer is such a complex and often confusing prospect. It also illustrates why results from any individual study must always be examined in the wider context of the research that has gone before. (Which is, let’s just note here, precisely what AICR/WCRF’s expert reports and Continuous Update Project [CUP] do.)

Researchers at California’s Stanford Prevention Research picked 50 foods at random from a cookbook and entered them into a research database to see how many had been associated with cancer risk — either raising or lowering it — by individual studies. For 40 out of the 50 foods, their searches turned up studies that suggested some effect on cancer risk. Upon closer examination, the researchers concluded that many of these reported associations were weak — certainly too weak to justify someone concerned about cancer risk changing her/his diet to include or exclude the foods in question.

Here at AICR, we fund a lot of studies that find associations between specific foods or food components and cancer risk. But we know that finding an association, in and of itself, is only the first step.

Preparation of AICR/WCRF experts report and CUP reports begin with a similar process of database searches. But it’s what comes next that counts — years of refining our searches by eliminating studies that do not meet our rigorous, systematic criteria for consideration, looking for agreement among studies of different types. This is the real work that allows us to distinguish consistent patterns in the data from the noise — patterns that lead, eventually, to our evidence-based advice.

We agree with the authors of the AJCN paper that the findings of individual studies can confuse and mislead. It’s only by looking at the totality of evidence in a systematic way that meaningful conclusions can be drawn. And a clear conclusion is that our diet can reduce the risk of cancer. There is a strong link, for example, between eating foods high in fiber and reduced colorectal cancer risk.

In our Foods That Fight Cancer web resource, we are always careful to place emerging data in the greater context of what previous research has shown.

And that’s why you can trust AICR’s Recommendations for Cancer Prevention, which distill thousands of studies into 10 simple statements for living healthier and longer.


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