Nutrition Science and Everyday Application - beta v 0.1

100 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
Figure 2.5. A sample page from the NHANES Food Questionnaire.
A third challenge in nutrition research is that diet is just so complex. Stanford
physician and researcher John Ioannidis, a frequent critic of observational nutrition research,
described the complexity of diet in a 2018 editorial published in JAMA: “Individuals consume
thousands of chemicals in millions of possible daily combinations. For instance, there are
more than 250,000 different foods and even more potentially edible items, with 300,000
edible plants alone.” He also points out that how an individual responds to a particular
dietary pattern can be influenced by genetics, age, and the way they metabolize nutrients.
“Disentangling the potential influence on health outcomes of a single dietary component
from these other variable is challenging, if not impossible,” Ioannidis wrote. 3