"Sorry, apple lovers (and doctor haters). An apple a day does not keep the doctor away, at least according to a new study. The study, published Monday in an April Fools edition of the journal JAMA Internal Medicine, was done for fun and "is very tongue in cheek," says lead researcher Matthew A. Davis, an assistant professor at the University of Michigan's school of nursing."The study involved 8,728 U.S. adults who participated in the National Health and Nutrition Examination Survey. Based on the survey responses, the participants were divided into two groups: 1) those who ate an apple a day, and 2) those who did not. The measured outcome was whether or not the participants made more than one visit (self-reported) to a physician over the past year (i.e. more visits than an annual physical exam).
Interestingly 753 (9%) subjects ate an apple a day compared to 7646 (91%) who did not. Those who did eat an apple a day "had higher educational attainment, were more likely to be from a racial or ethnic minority, and were less likely to smoke," and so there was selection bias with the apple-eaters tending to adopt healthier behaviors overall.
The initial analysis showed that apple eaters were more likely to keep the doctor away: "39.0% of apple eaters avoided physician visits vs 33.9% of non–apple eaters (P = .03)." This difference was deemed to be statistically significant, but the next step was to control for the selection bias and try to eliminate the effects of confounding factors (i.e. other associated healthy behaviors in the apple-eaters):
"After adjusting for sociodemographic and health-related characteristics, however, the association was no longer statistically significant (OR, 1.19; 95% CI, 0.93-1.53; P = .15)."Note that the odds-ratio (OR) is still greater than 1 indicating that apple-eaters do avoid doctor visits more than the non-apple-eaters even after adjusting for confounding variables, but the difference is no longer statistically significant with the p-value greater than 0.05.
However, how do these results jibe with what we know about the healthful benefits of eating fruits and vegetables? To recap, fruits and vegetables have a number of long-term health benefits. Most notably, they help to prevent obesity "when consumed in place of more energy-dense foods." In other words, they possess fewer calories than foods like junk food that are often eaten as an alternative to fruits and vegetables. In addition, fruits and vegetables contain many valuable nutrients including potassium, dietary fiber, folate (folic acid), vitamin A, and vitamin C. Moreover, they are low in harmful content such as trans/saturated fat, sugar, and salt (sodium chloride).
For example, "[r]esearchers found that people in the study who left fruit on their countertops weighed an average of 13 lbs. (6 kg) less than those who didn't have this healthy snacking option within arm's reach." In other words, eating an apple a day may substitute for eating a bag of chips a day.
Indeed, there are other studies that "have found numerous possible health benefits associated with apple consumption, including weight loss, reduced cancer risk and improved cardiovascular health." Moreover, one should not ignore that in this study, that apples did indeed seem to (slightly) keep the doctor away even although the difference was not statistically significant and could have been due to chance. A bigger study could resolve this question more definitively.
The moral of the story is that in the short run for a relatively healthy person an apple a day may not significantly impact one's health. In the long run, increased fruit and vegetable consumption including apples can lower the risk of obesity resulting in numerous health benefits that may indeed keep the doctor away.
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