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World-wide acceptance
Program developed at Iowa State making its way around the world.
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Once the statistical method got accepted in the United States, it was
only a matter of time before other countries began to use it.
That time has come for the ISU Method, a statistical method developed
on campus to analyze dietary intake data. In combination with the Dietary
Reference Intakes (DRIs) established by the National Academy of Sciences,
the method permits assessing, for example, the nutritional status of a
group of individuals.
The DRIs have recently replaced the old Recommended Daily Allowances method
of determining nutritional requirements.
The ISU Method not only gained acceptance from the United States Departments
of Agriculture (USDA) and Health and Human Services (HHS), but by governmental
agencies in New Zealand, Canada and Portugal.
And recently, one of the developers of the ISU Method, Alicia Carriquiry,
professor of statistics, spent four days in Colombia where she advised
the Colombia Department of Family Services on the design and analysis
of the first national dietary intake survey in that country.
"Each country is interested in utilizing the ISU Method for different
things," Carriquiry said. "Because the United States is a developed
country they might be interested in finding out information on excessive
consumption leading to obesity or on the consumption of ‘non-standard’
nutrients such as omega-3 fatty acids.
"Developing countries like Colombia, where 60 percent of the population
is unemployed, are worried about more basic issues including the consumption
of some pretty basic nutrients such as macronutrients and vitamins."
Colombia has a population of 40 million people, some spread out in extremely
remote areas making the capturing of data even more difficult.
It's difficult enough in the United States to get a good handle on the
nutritional intake of its citizens.
Carriquiry says most survey instruments used in dietary surveys just record
what an individual has eaten in the past 24 hours. Individuals are asked
not only to recall the types of food they have eaten, but the amounts
as well.
"It's tough for researchers to analyze that information from a statistical
point of view," she said. "Nutritionists are interested in the
usual, rather than the daily consumption of nutrients."
For instance if you eat carrots or spinach during the day you are surveyed,
then your Vitamin A intake will be very high for that day. But Carriquiry
says if you are surveyed and haven't eaten a carrot or spinach salad in
the previous 24 hours, then your Vitamin A content will appear very low.
"Survey data that capture consumption over one day are not a good
representation of what you are getting over the long-term," she said.
"The ISU Method accounts for the day-to-day variability in intakes
allowing us to estimate a better distribution of dietary intake for a
particular population.
"From a statistical standpoint, it is surprisingly difficult to work
with this type of data," she continued. "The ISU Method is a
complex statistical procedure, but we can deliver pretty good estimations
to nutritionists."
The ISU Method was developed by Carriquiry; Sarah Nusser, professor of
computer science; Wayne Fuller, emeritus Distinguished Professor of statistics;
and former graduate student Kevin Todd, now at the National Cancer Institute.
Carriquiry and the others have worked with a wide variety of governmental
agencies over the years including the National Center for Health Statistics
of the Centers for Disease Control and Prevention, the National Data Laboratory,
the Food and Nutrition Service, the Center for Nutrition Policy and Promotion
of the USDA and the World Health Organization.
Carriquiry has served five years on an Institute of Medicine committee
that established guidelines for analyzing and interpreting dietary intake
data.
Around LAS
December 6-19, 2004
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