Davis et al. (2015) set out to empirically test the popular saying "an apple a day
keeps the doctor away." Apples are often used to represent a healthy lifestyle, and
research has shown their nutritional properties could be beneficial for various
aspects of health. The authors' unique approach is to take the saying literally and
ask: do people who eat apples use healthcare services less frequently? If there is
indeed such a relationship, they suggest, promoting apple consumption could help
reduce healthcare costs. The study used publicly available cross-sectional data from
the National Health and Nutrition Examination Survey. Participants were
categorized as either apple eaters or non-apple eaters based on their self-reported
apple consumption in an average 24-hour period. They were also categorized as
either avoiding or not avoiding the use of healthcare services in the past year. The
data was statistically analyzed to test whether there was an association between apple
consumption and several dependent variables: physician visits, hospital stays, use of
mental health services, and use of prescription medication. Although apple eaters
were slightly more likely to have avoided physician visits, this relationship was not
statistically significant after adjusting for various relevant factors. No association
was found between apple consumption and hospital stays or mental health service
use. However, apple eaters were found to be slightly more likely to have avoided
using prescription medication. Based on these results, the authors conclude that an
apple a day does not keep the doctor away, but it may keep the pharmacist away.
They suggest that this finding could have implications for reducing healthcare costs,
considering the high annual costs of prescription medication and the inexpensiveness
of apples. However, the authors also note several limitations of the study: most
importantly, that apple eaters are likely to differ from non-apple eaters in ways that
may have confounded the results (for example, apple eaters may be more likely to
be health-conscious). To establish any causal relationship between apple
consumption and avoidance of medication, they recommend experimental research.