This news release, issued by Edelman, a public relations firm, on behalf of the Pear Bureau Northwest, a pear marketing group, is a textbook example of how to conflate “correlation” with “cause and effect,” and confuse consumers all the way to the fruit aisle. The release describes results of an “analytic,” observational, data-mining study of some subset (readers never learn what subset, exactly) of pear-eating people among participants in the 2001-10 National Health and Nutritional Examination Survey of adult Americans. The data suggested that people who reported eating pears had a “lower” body weight than non-pear eaters and were “35 percent less likely to be obese.” From there it leaps to the idea that there are health benefits to eating a “pear a day,” attributing the benefits to the relatively high fiber content of the fruit. Although the release notes that the data suggest eating fresh pears “should be encouraged” as part of an “overall healthy diet;” and the lead investigator acknowledges in a quote that this is an “association” or “correlational” study, the body of the release offers no data to support the notion that pears are more likely than any other fiber source or food to actually reduce weight or obesity. It offers no information (as did the study, published in the journal Nutrition and Food Science) about the participants or the strengths/weaknesses of the correlation. And above all it fails to note that those who reported eating pears were older and seemed to be more health-conscious — they drank less alcohol and smoked less — all of which could have contributed to or even accounted for the lower body weight and lower risk of obesity. Most of the release is a predictable promotional piece for the wonders of Barletts and Boscs, noting of course that they are “cholesterol-free,” “fat-free” and potassium-rich.
The release is likely to have some readers believing that pears potentially play a key role in stopping the obesity epidemic; oh, that it were so. Predictably, a couple of online news articles got the (wrong) message, including this one: “A Pear a Day Keeps the Pounds Away” (UK’s Daily Mail). Consumers already have a big problem figuring out healthy diets and healthy weight loss programs. The hope is that the agricultural marketing industry will help educate consumers, not mislead them.
If consumers are encouraged to eat a pear a day it would be helpful to include even a ballpark cost. Fresh pears may be available in all markets year-round but the cost rises substantially when they have to be shipped long distances.
The release, as noted above, says pear consumers had a lower body weight and were “35 percent less likely” to be obese compared to non-pear consumers, but there is no hint of context. Was this over time? Did the correlation vary according to age groups? (The age ranged from 19 years old to senior status.) What were the absolute numbers? The release does state that the study found no differences in calories (energy) intake and physical activity between the pear eating and non-pear eating group. And while it mentioned that the analysis looked at cardiovascular risk factors, it was silent about any differences (or lack thereof) in cardiovascular disease (CVD) or CVD risk in pear eating and non-pear eating subjects.
Aside from the poorly quantified main point about the association between pear consumption and body weight, the release did mention some of the dietary benefits of pears: “Pears are an excellent source of fiber and a good source of vitamin C. One medium pear provides about 24 percent of daily fiber needs for only 100 calories. They are sodium-free, cholesterol-free, fat-free and contain 190 mg of potassium.”
The study looked at a possible association between pear eating and obesity but the protocol did not have a way to determine harms of eating or not eating the fruit. In any case, it’s hard to imagine any.
The release sorely needed details about the make-up of the data set that was analyzed, along with information about the limitations of epidemiological correlation studies. The study was based on a survey of a group of people deemed representative of the nation, but we aren’t even told how many people were surveyed.
The release didn’t list any of the limitations to the study, including the many variables that could have affected the outcome. The only common factors among the groups was that they either ate pears or they didn’t. What else was different? Was age taken into account as a variable in making the association since metabolism may slow down? Was gender taken into account due to weight gain during pregnancy or menopause? What about education and economic status? Although these variables are mentioned in the published study, the release could have mentioned briefly that other factors were taken into account.
The published study also described the number of participants (24,808 respondents) as small for a national epidemiological study and stated that it is an observational study of a subset whose “data cannot be used to draw causal relationships.”
It’s not “mongering” to acknowledge the obesity epidemic in the United States so we give this a Satisfactory.
The release is transparent in acknowledging that the Pear Bureau is the source of its pear promotion and the “commissioning” of studies, in this case at the Louisiana State University Agricultural Center.
Like Macy’s and Gimbel’s, commercial competitiveness is unlikely to lead the Pear Bureau to carry water for, say, the Banana Bureau, or the Peach Bureau. But the release would have been strengthened by more explicitly noting the potential role of other high-fiber fruits and foods in a good diet.
There was no mention of other alternatives to weight loss on a dietary or any other level. This article almost makes it seem that pears are the greatest solution. But when we compare the 4 grams of dietary fiber in pears with other fruit we find that a large apple contains 4.5 grams and 3 dried figs have 10.5 grams.
The release goes into some detail about the wide availability of pears in the United States.
With or without pear eating. it is not exactly news that higher consumption of fruits (and vegetables) have long been associated with better overall diets, nutritional status, and healthy weight.
The quoted lines from the lead investigator are carefully phrased, but the overall release is misleading to suggest pears alone are a solution to the obesity problem. But since we’ve already raised that concern elsewhere in the release we’ll give the benefit of the doubt here.