This news article reports on a published study that, according to its Harvard authors, establishes a fairly strong link between “Western” diets rich in red meat, sugar and fat and an increased risk of death not only from all causes (such as heart disease), but also specifically from prostate cancer in men diagnosed with prostate cancer and treated before the cancers had spread. The researchers assessed the dietary habits of 926 physicians with such prostate tumors, all of them participants in a longstanding and ongoing Physicians Health Study, and who filled out a yearly series of questionnaires about their health status. The researchers cautiously conclude that although the study was “observational” and had a number of shortcomings, it adds evidence that prostate cancer patients may be more likely to survive and thrive by adopting healthier plant-based diets.
The article does a pretty good job of noting that implementing these healthy dietary recommendations may reduce the risk of death from other diseases as well as prostate cancer. But the story goes too far in its attempt to create urgency around the results. It resorts to a fear-mongering headline and glosses over all of the extensive limitations discussed by the investigators themselves in the study. It also never cautions that such a study can’t show a cause-and-effect relationship between diet and death, and thus it overstates the strength of the evidence for a diet-death or diet-protective link.
Several aspects of this study make it newsworthy, including the fact that very little has been proven about the impact of diet on the quantity and quality of life in men diagnosed with non-metastatic prostate cancer, even though there have been tantalizing suggestions that plant, fish, and grain-based diets have real (and positive) impact on the biology and progression of prostate tumors. Because prostate cancer is the most prevalent cancer and the second biggest cancer killer in American men, serious evidence for the impact of a prudent diet already likely to decrease risk for heart disease, Alzheimer’s Disease, obesity-related illness, and other cancers, is potentially of enormous value to overall public health. Long-term observational studies designed to identify the scope and strength of risk factors have proven their worth over time, and the Physicians Health Study is an exemplar. So men, and the people who care about and for them, will understandably latch on to any evidence perceived as “proven” to increase prospects for a longer, healthier life after prostate cancer.
We’ll rule this Not Applicable. The article could have noted that a Mediterranean-style diet heavy with fish, olive oil, fresh vegetables, fruit, and whole grains is almost always more expensive than the typical fast, french-fried, and burgered Western diet. But we won’t penalize the story for not mentioning this fact. The report does notes that it “doesn’t take a whole lot of adjustment” to lower risks with a better diet, and it takes some pains to note that a prudent diet already is widely recommended to ward off other disorders.
The story reports relative risks and not absolute risks, which is one of our concerns with the coverage. It mentions, for example, that the researchers studied 926 men who had prostate cancer that had not spread and that those who ate the Western diet were 2.5 times more likely to die of their cancer than men on a prudent diet. But our question in this situation is: 2.5 times more likely than what? Reporting the absolute rates of death would give readers a better grasp on the scope of the problem and potential benefits.
We won’t flag the story for not discussing the potential harms a Mediterranean style of eating — which don’t really merit much discussion.
There were several problems with the story’s presentation of the evidence. As noted above, some comment was needed about the fact that this is observational research and not a clinical trial. Therefore, the research cannot prove that any type of diet will “kill” anyone. And while the story says the “average” American diet is to blame, it never clarifies that the researchers were comparing those with the worst “American diet” scores to those with the best scores. What these men were actually eating is not reported in the study, so it’s difficult for any individual to say how their own diet might stack up against these results. But for those somewhere in the middle, the findings are clearly not as worrisome, and the story could have pointed this out. Lastly, the story talks about the thousands of doctors that are enrolled in this giant research project, but it never cautions that these findings are based on a very small number of deaths. For example, only 9 men died in the group that had the best “American diet” score compared with 21 in the group with the worst score — that’s where the story gets the “2.5 times as likely to die” figure. As the researchers point out, the small number of deaths suggest “caution in the interpretation of the results.”
The fear-mongering headline of this story was out of step with the strength of the findings. We’d note that journalists often have no control over the headlines of their stories, but it’s a problem that can’t be overlooked here.
News articles always come out stronger when sources other than those with a stake in a study’s findings are sought out and quoted. In this case, an additional comment from a nutritional epidemiologist not involved in this study would have provided context.
The story doesn’t address anything, beyond diet, that prostate cancer survivors might do to reduce their risk of recurrence and death. But since there aren’t necessarily any interventions that are proven to reduce recurrence, we’ll give the story the benefit of the doubt here and call it Not Applicable. To meet this criterion, the story could have mentioned androgen deprivation therapy, which is used in some cases to prevent recurrence. Other lifestyle interventions that are associated with reduced risk for all-cause mortality (eg, exercise) also could have been mentioned.
With some notable exceptions, such as “food deserts” in areas of high poverty, prudent diets are widely accessible and the article spells this out pretty well.
The article does a good job of noting that hard data are scarce for the impact of diet on this population of men with cancer, and of the unexpected finding of increased (risk of) prostate cancer- specific deaths. And we liked the way it presented the study results as “yet another piece” of evidence for the benefits of a healthy diet, rather than something entirely “new.”
A news release was issued by Harvard’s school of public health about these findings. The story includes quotes from the same Harvard researcher who is quoted in the news release, but the quotes are different, suggesting that original reporting was done. This makes the grade for Satisfactory.