Nutrition Science and Everyday Application - beta v 0.1

98 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
CHALLENGES IN NUTRITION RESEARCH
How does the food we eat affect our health? This question is exceedingly difficult to answer
with certainty. We all need to eat every day, but we can choose from a huge array of
possible foods in different combinations. And it’s probably not what we eat on any given day
that matters, but what we eat over months and years and decades—our long-term eating
patterns—that matter to our long-term health.
Imagine that you’re a nutrition researcher, and you’ve made the observation that over
the last 50 years in the U.S., people have been consuming more and more processed foods
(foods made with refined ingredients and industrial processes, usually with the addition of
sugar, fat, and/or salt). You hypothesize that processed foods are contributing to obesity,
which has also increased over the last 50 years. You might first test your hypothesis in
animal studies by feeding mice and rats a buffet of potato chips, soda, and Twinkies, and
measuring changes in their body weight. You might find that the animals do, in fact, gain
weight on this diet. However, you know that what is true in rodents isn’t always true in
humans, and you’ll need to study humans in order to understand the role of processed foods
in the obesity epidemic.
Your next step might be to conduct an observational study, the most common type of
study design in human nutrition research. For example, you might do a cross-sectional
study where you compare groups of people who eat a lot of processed foods with those who
eat very little. Or you might conduct a prospective cohort study in which you ask people