The reporter discusses this study, which was published online today in the journal Pediatrics, on dietary fiber and breast cancer risk. The data come from the Nurses Health Study II which is investigating the relationship between oral contraceptives, diet and lifestyle risk factors and overall health in 116,686 women. The researchers started following these women in 1989, when they were between the ages of 25 and 42.
In 1998, 44 263 of these women were asked questions about their diet during high school; since then, 1118 of these women have developed breast cancer. Based on their analysis the researchers conclude,”Among all women, early adulthood total dietary fiber intake was associated (my emphasis) with significantly lower breast cancer risk.”
Note the words I emphasized: “was associated.” That’s precisely what this study showed. Why use the word “associated?” Because this is an epidemiology study. This type of study can show a correlation, but it cannot prove causation. It’s possible that the women who said they ate more fiber as teens had other aspects of their life–a good diet, exercise, not smoking, etc.–that also played a role in reducing their breast cancer risk. It’s also possible that many of these women misreported what they ate as adolescents, since they were answering questions about what they ate as teens when they were between the ages of 35 and 52.
Before discussing their own research, the study’s authors explain, “Previous studies of fiber intake and breast cancer have almost all been nonsignificant, but none of them examined diet during adolescence or early adulthood, a period when breast cancer risk factors appear to be particularly important.” Yet, what’s the NPR headline: A Diet High in Fiber May Help Protect Against Breast Cancer.” Umm, not really.
And what does the NPR reporter say about the study: “… if you’re skimping on fiber, the health stakes are high, especially if you’re a teenage girl. A study published Monday in the journal Pediatrics concludes that eating lots of fiber-rich foods during high school years may significantly reduce a woman’s risk of developing breast cancer.” Umm, not really, either.
As you now know from what I explained earlier, the study did not conclude “eating lots of fiber rich food may significantly reduce” breast cancer risk. It concluded, “a higher fiber intake was associated with lower breast cancer risk and suggests that intake during adolescence and early adulthood may be particularly important.”
We should all–adults and adolescents alike–eat a high fiber diet. It helps maintain a healthy weight and helps decrease risk for heart disease and diabetes.
We should all also pay close attention to the types of studies journalists report, and how they report them. Here’s what the researchers conclude:
The findings in this large prospective study support the hypothesis that consumption of foods high in fiber reduce breast cancer risk. These results also suggest that dietary fiber intake during adolescence and early adulthood may be particularly important. Our findings are in line with the American Cancer Society guidelines to consume foods rich in fiber such as fruits, vegetables, and whole grains, and indicate the importance of adopting these food choices during childhood and early adult life.
The reporter should have reached the same conclusion too.
Tip of the hat to MR for getting me to write about this by suggesting the headline.