Chewing over the numbers

Lea Petersen

An ISU professor is attempting to change the way food is researched. 

Alicia Carriquiry, distinguished professor of statistics, presented her research on measuring dietary intake and nutrient consumption in “Chewing over the Numbers: How Food Consumption Data Are Driving Nutrition Policy.”

“I think it’s probably the most important work that I have done here at Iowa State,” Carriquiry said.

Carriquiry said almost $70 billion is spent on food assistance per year in the United States. This food assistance includes food stamps, school lunches and breakfasts, and women, infant and children programs.

Statistics play a critical role in analyzing the collection of food consumption, monitoring food and nutrient intake, estimation of the prevalence of inadequate or excessive consumptions, and planning interventions to address inadequacies, Carriquiry said.

Previously, large-scale studies were collected using “24-hour recall instrument.” In this process, a researcher calls the participant and asks what he or she ate within the last 24 hours. Participants reported what food they ate, what amounts and on what occasion.

“This is not accurate always because of social pressures. Women tend to underreport ‘sinful’ foods, and men tend to underreport alcohol. Serving sizes are also not uniform,” Carriquiry said.

There was, however, an Achilles’ heel to the 24-hour recall instrument.

“The daily intake of a nutrient is really not that important,” Carriquiry said. “What matters is that you eat enough nutrients on average to maintain a healthy lifestyle. If we could observe the usual intake, we could predict the outcomes of the likelihood of disease on an individual level. ” 

It would be best if participants could be observed for at least 100 days, Carriquiry said.

“Day-to-day variability in intakes is not homogeneous across persons. But you can’t observe people for a long time because of cost and because people get tired of you,” Carriquiry said.

A person may consume something today, but not for two weeks after.

Carriquiry helped develop software that has now become the standard in measuring nutrient consumption. In 2000, the National Academy of Sciences of the United States recommended that Iowa State’s method should be used as the official method in measuring dietary intake, and in 2002 a European consortium of scientist echoed their praise.

“This was an honor for us,” Carriquiry said.

Because of the new software, food assistant programs have been modified to better increase the correct nutrients. The World Health Organization funded a revision of Iowa State’s software to make it more easy to use in 2008.