This report on a study about the links between calcium intake and cancer risk does several important things well:
The story’s biggest shortcoming is a failure to put the relative risk reductions in the context of absolute risk. It’s hard to tell how meaningful a 20 percent risk reduction of head and neck cancer is. One suspects the 7-year risk of those cancers in this population is very small, but we don’t know.
There’s also an issue that isn’t captured by the criteria in this review but is worth mentioning nonetheless. It appears that most dietary calcium came from dairy products. If that’s true, do the researchers know whether something in the dairy products other than the calcium that is responsible for the risk reduction? The fact that calcium supplementation didn’t have the same protective effects as calcium-rich foods raises the question. The reporter should have too.
It’s not necessary to compute the marginal extra costs, if there are any, of a diet high in calcium.
The study cites a few benefits linked to supplements, but they are not central enough to the story to require discussion of costs.
The reporter generally does a good job explaining which levels of calcium intake showed benefits against which cancers in both men and women. It names the cancers that were reduced the most and least by calcium intake. It mentions those that appeared to be linked to supplements rather than food.
But the report fails to put the risk reduction numbers in the context of absolute risk.
The study shows men with high calcium intake were 16 percent less likely than those with the lowest calcium intake to get colon cancer over 7 years. But it fails to tell us how big the underlying colon cancer risk is for these men. If that risk is 1 percent, a 16 percent drop in that risk is of little significance. If the risk is 40 percent, that’s very different.
The story fails to mention the risks of excessive calcium intake, which include kidney problems and malabsorption of other minerals. As a matter of course, such risks should be mentioned at least briefly.
Having said that, the reporter gets points for stating that intake levels above 1,200 milligrams per day did not show addiitonal benefits. This should be sufficient to prevent people from taking reckless action to boost their calcium intakes to very high levels.
The report does a commendable job of describing the strengths and weaknesses of the study, as well as its methodology and study population, without using jargon.
The reader comes away understanding that the study was big but not as rigorous as some smaller trials. The reader understands that the results are not conclusive. The comment at the end, indicating that the study group is likely healthier than the population as a whole, is particularly useful.
The story does not exaggerate the severity or prevalence of the 10 types of cancer studied. Nor does it dramatize the potential of calcium to prevent cancer.
For such a short story, the reporter does a good job of sourcing. The story includes the thoughts of the lead researcher and three independent experts.
It’s worth pointing out that none of the experts is quoted directly; their viewpoints are paraphrased. Other reporters might have made only two calls and included live quotes. Those stories likely would have less credibility, not more.
The study is about the benefits of higher calcium intakes, and it distinguishes properly between calcium from diet and supplements.
There are certainly other ways to reduce cancer risk in the studied population, but the story is framed in a way that makes it unncessary to get into that.
The availability of calcium-rich foods and calcium supplements is not in question.
The story makes no claims for the novelty of a calcium-rich diet or the study’s general findings.
There is no evidence that the reporter drew excessively on the press release linked to the study.
Systematic, Criteria-Driven
Monday at #ADA2021, an infectious disease epidemiologist, a journalist, and a researcher shared perspectives on communication of risk in the era of COVID-19: http://ow.ly/ROfR30rMeE7 @AstleyCM @garyschwitzer @berthahidalgo @ADA_DiabetesPro
Shoutouts to @susan_bewley @drkevinknopf @MichaelBaum11 in this call for more than fawning coverage from press releases for these kinds of stories.
Also, linked history inside goes back 5 years just on Grail apparently trying to become Holy Grail. https://twitter.com/garyschwitzer/status/1408849696416841731
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