Center's Unconventional Services Provide Unique Approach to Nutrition Research

Twenty years after being created, the Diet Assessment Center continues to play an integral role in many collaborative applied nutritional sciences research projects

Researchers in Penn State’s Diet Assessment Center (DAC) have an unusual approach to conducting research: they like to surprise their participants. They’ve taken this approach since the DAC was created, and it’s one of the center’s main assets.

When people enroll in a study on which the DAC collaborates, they provide general times of availability during the day. After that, they go about their normal lives. One day, they will receive a call from the center—whether they are at work, stuck in traffic, or in front of the TV at home—and they will be asked to recall every morsel of food or drink they’ve consumed in the previous twenty-four hours, or what the researchers call a dietary recall.

portion of food chart used by researchers in the Diet Assessment Center

Participants in Diet Assessment Center studies are given charts that help them estimate the volume of food they have eaten in the past twenty-four hours. Above, a bowl found on a chart used in some DAC studies (the full chart contains bowls, wedges, and other shapes of various sizes).

Image courtesy: Nutrition Consulting Enterprises, P.O.Box 1255, Rt. 30 Station, Framingham, MA 01701

Some people, faced with the prospect of recalling a day’s worth of food, might feel uncomfortable, self-conscious, or embarrassed. If given the chance to plan for a dietary recall, they might eat healthier foods than they normally eat—which would skew the results of research. By using a candid calling approach, DAC researchers, led by Diane Mitchell, coordinator of the DAC, and Dr. Terry Hartman, associate professor of nutritional sciences, aim to catch people off guard and get a realistic look at diets.

Recalling exactly how much you ate in the last day may sound challenging, but the center provides helpful ways to remember. Each participant is given a food chart (see image), which contains estimated volumes for different shapes of food. Participants can say, “I had three oatmeal raisin cookies, size B4.”

To maximize the accuracy of results, the Diet Assessment Center uses a dynamic food database that contains 18,000 foods and over 7,000 brand-name products that are updated by researchers at the University of Minnesota. This database automatically calculates how many vitamins and essential minerals participants are consuming, as well as other nutritional data: fat, calories, protein, etc. What they track varies for each study.

The center typically calls each participant on three days in a given two-week period. Those days are randomized, too, which adds another layer of candidness to the recalls. “We follow a standard protocol that is widely accepted,” says Mitchell.

Dr. Tanja Kral ’01g, ’03g NUTR, assistant professor of nutrition and psychiatry at the University of Pennsylvania School of Medicine, has worked with the DAC on several projects. "The Diet Assessment Center has provided us with an outstanding service. The collection of self-reported dietary intake data can be a challenging task. Their team uses highly trained interviewers and standardized techniques to enhance the accuracy of self-reported data," she says. In addition to collecting data efficiently, the center provides expert analysis and detailed instructions for interpreting the outputted data from the dietary recalls, says Kral.

When the center’s ability to create detailed lists of participants’ eating habits and nutritional intake is paired with other types of data collection, the potential for understanding links between eating and health outcomes becomes vast.

One ongoing project in the center is looking at how oxidative stress (an imbalance in certain chemicals in the body that contain oxygen) can affect pregnancy outcomes. The researchers aim to determine whether certain dietary factors put women at risk for delayed conception or loss of pregnancy. Increased oxidative stress has been linked to DNA and tissue damage, which can lead to reproductive problems in men and women. However, some research indicates that consuming certain antioxidant vitamins (C and E) and carotenoids (pigments naturally found in certain foods) can reduce oxidative stress. In this study, dietary recalls estimate how much of these and other antioxidants pre-pregnancy men and women are consuming. Paired with blood and urinary sample measures of biomarkers of oxidative stress, the dietary recall is invaluable and will help to advance the understanding of how diet contributes to reproductive health.

image of Diet Assessment Center

Not only is the Diet Assessment Center important for research, but it serves as a training ground for aspiring dietitians.

Other ongoing projects examine different populations, and each project has a different aim. One project is testing a method for improving nutritional status in older adults who have been diagnosed with cancer. Another is looking at whether or not consuming fruits and vegetables combined with exercise will improve weight status in 10- and 12-year-old children. Another project is focused on nutrition risk screening in older adults living in rural areas.

While phones are the main medium for assessments, the Diet Assessment Center also uses online diet assessments in some studies, which give participants round-the-clock access to log food they’ve eaten.

Not only is the Diet Assessment Center important for research, but it serves as a training ground for aspiring dietitians. As a student, Jessica Burgland ’10 NUTR worked for several semesters in the center, conducting dietary assessments. “My involvement in these research projects gave me an idea of what our culture is eating. It’s interesting to see how different age groups eat different things,” she says.

Current Projects

A selection of ongoing projects in the Diet Assessment Center includes:

Geisinger Rural Aging Study (GRAS)
Funded by the U.S. Department of Agriculture, Agricultural Research Service (Principal Investigator: Dr. Chris Still, Geisinger Health System; Investigators: Dr. Terry Hartman and Dr. Gordon Jensen, professor and head of the Department of Nutritional Sciences). The overall study involves ongoing nutrition risk screening in 20,000 older adults living in Pennsylvania. The DAC in collaboration with Tufts University has developed a food frequency questionnaire that is currently being validated in a subset of 225 of these older adults. This study will compare questionnaire data with dietary recalls and other selected biochemical measures of nutritional status.
Antioxidant Status, Diet and Early Pregnancy (ISIS)
Funded by the National Institutes of Health (Principal Investigators: Dr. Marlene Goldman, Dartmouth College and Dr. Terry Hartman). The DAC is collecting telephone dietary recalls in 500 healthy women and their partners who are planning pregnancy. This is a prospective cohort study to evaluate the effects of antioxidant intakes on pregnancy outcomes.
RENEW (Reach Out to Enhance Wellness in Older Survivors)
Funded by the National Institutes of Health (Principal Investigator: Dr. Wendy Demark-Wahnefried, University of Alabama at Birmingham). The DAC is collecting dietary recalls and a variety of other telephone interviews that will be used to assess nutritional status, physical activity, functional status, demographics, and other health status information from 680 older adults who have been diagnosed with colorectal, breast, or prostate cancer five or more years prior to their enrollment. The purpose of the study is to improve functional and nutritional status through a personally tailored program of telephone counseling and mailed materials.
Obesity Prevention Tailored for Health II (OPTII)
Funded by the National Institutes of Health (Principal Investigators: Dr. Kim Reynolds, University of Southern California and Dr. Terry Hartman). The purpose of the study is to evaluate an innovative nutrition intervention targeting children age 10-11 and their parents to prevent obesity and increase fruit and vegetable intakes of these families. The DAC will collect dietary recalls in 400 children at baseline, six months, and one year.
Northeast Pennsylvania Colorectal Cancer Study
Funded by the Pennsylvania Department of Health (Investigators: Dr. Philip Lazarus, Penn State Hershey Center Institute and Dr. Terry Hartman. The study is being conducted in approximately 2,000 participants in Northeastern Pennsylvania where the incidence of colorectal cancer is high. The DAC is collecting dietary data using a modified food frequency questionnaire data to examine the effects of red and processed meat consumption, meat cooking methods, and dietary carcinogens on the risk for colorectal cancer.


Editors: Diane Mitchell can be reached at or 814-863-5955. For additional information, please contact the College of Health and Human Development Office of College Relations at 814-865-3831 or