Fiber and breast cancer risk: holes in Harvard news release set stage for misleading news coverage

Today we’ve published three reviews that look at media messages related to a Harvard study on fiber consumption and breast cancer risk.

• Harvard news release review: Are we absolutely or relatively sure that increasing dietary fiber reduces breast cancer risk?
• NPR story review: How big is the reduction in breast cancer risk linked to a high-fiber diet? 16 percent or 0.2 percentage point?
• CBS story review: Multiple perspectives elevate CBS coverage of diet-breast cancer link

This is the kind of questionnaire-based diet study that the news media typically do a poor job of communicating about, mainly because journalists don’t give readers a fair sense of the many significant limitations of this type of research.

But as we’ve repeatedly pointed out, there are a host of players who have an opportunity to either pollute the health news stream with misinformation or help keep it running clear with balanced perspectives. Those players include public information officers who write news releases about these types of nutrition studies.

In this case study, we found that many of the deficiencies we identified in news stories about the study were present in the Harvard news release that announced the results to the world. Our reviewers found that the news release and both news stories shared the following shortcomings:

• Reporting only of misleadingly high relative risk reductions (e.g. 16% to 24%) when the absolute difference is cancer rates was a tiny 0.2 percentage point.
• Use of active verbs in the headline to describe the effects of fiber on cancer (e.g. fiber “may cut,” “may help protect”) when this type of study can’t prove a cause-and-effect relationship.
• No discussion of alternative lifestyle approaches that may help reduce breast cancer risk.

Of course, we don’t know to what extent these news stories may have relied on the Harvard news release in their coverage, and it’s clear that both stories did go beyond the news release to include outside perspectives on the research. We applaud both of these stories for touching on the problems inherent in research that asks participants to recall their dietary habits from many years ago.

Nonetheless, the fact that neither of these stories gave readers a sense of the actual cancer rates observed in the high- and low-fiber groups (3.3% vs. 3.1% — a 0.2 percentage point difference) represents a fundamental flaw and overstatement of the results. And this flaw was present not only in the study itself, but also in the Harvard news release that likely served as a starting point for many journalists covering the story.

Harvard is widely regarded as an institution that sets the standard in scientific research, especially with respect to nutrition. We’d love to see their news releases do a better than this one did of elevating the public discussion in this area.

Kevin Lomangino is managing editor of HealthNewsReview.org.