Fall 2008

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Statistics Makes Sense of Dietary Data

Statistician Alicia Carriquiry and colleagues developed a new approach to analyzing dietary intake data that has been implemented worldwide.

Alicia Carriquiry has been a member of the Department of Statistics faculty since 1990, and has earned an international reputation for her work.

She also has a secret you won't find on her resume. The one undergraduate course she flunked... statistics.

Carriquiry (MS '86 statistics, PhD '89, DMJ '89 animal science) was born and raised in Uruguay. As an undergraduate, she majored in ag engineering, which in Uruguay is a five-year degree that includes agronomy and animal science.

She completed her master's degree in animal breeding and genetics at the University of Illinois and became interested in statistics after participating in a pig breeding conference at Iowa State in 1984. She completed her master's and doctorate at Iowa State, thanks to the encouragement of David Harville, who was on the statistics faculty at the time.

Much of Carriquiry's work has revolved around nutritional issues. In the early 1990s, the U.S. Department of Agriculture contacted Iowa State's Center for Agricultural and Rural Development (CARD) to see whether a new approach to analyzing dietary intake data could be developed. Carriquiry and colleagues from the statistics department began working with CARD on the issue in a collaboration that continues today.

"Nutrition researchers and policymakers are interested in estimating, for example, the proportion of individuals in a group whose intake of some nutrient does not meet their requirements," Carriquiry says. "To do this, it's necessary to know the distribution of habitual or usual intakes of the nutrient in the group."

Since it's not practical to observe the daily intake of a nutrient over many days for each person, most surveys simply collect information for one or two days. Carriquiry and colleagues developed what became known as the "ISU Method" - a way to estimate the distribution of usual nutrient intake in a group based on daily intake over a small number of days.

Carriquiry has been invited to participate in many international projects with nutrition as the focus. In the past few years, she has collaborated with officials in Canada, New Zealand, Colombia, Philippines, the Netherlands and Bangladesh. She's currently working with policymakers and researchers in Uganda, Chile and Palestine on the design, implementation and analysis of food intake surveys.

About 65 percent of Carriquiry's salary comes from the Iowa Agriculture and Home Economics Experiment Station and her ties to agriculture are strong.

"I do a lot of work related to agriculture," she says. "Currently I am a co-investigator on a grant from the USDA to look at the influence of ethanol on corn prices in Iowa and how that has affected the land-use choices farmers make and the consequent environmental impacts."

Carriquiry says statistics isn't just for academics or scientists, although she knows the general public doesn't share her opinion.

"The comment I get most often from 'normal' folk when they learn I am a statistician is 'icky pooh.' Statistics is critical! It lurks everywhere - from the news about financial markets, to who will win the elections in November, to how many servings of fruit we need to maintain health," she says. "It's too bad such an interesting, challenging, fun and important profession has such a poor reputation. We need to make statistics cool."

ISU Method takes nutritional surveys to the next level

Alicia Carriquiry teamed up with Sarah Nusser, professor of statistics, Wayne Fuller, emeritus distinguished professor of statistics, and former graduate student Kevin Todd, now at the National Cancer Institute to develop the "ISU Method". "The method consists of a series of steps that permit estimating the distribution of usual intakes of a nutrient in a group when all we can observe is daily intake over a small number of days for each person in the group," Carriquiry says. It has been widely accepted in the United States, the European Union and other countries.