So far, few FFQs have been developed to assess the diets of diabetes patients. Researchers at Taiwan's Kaohsiung Medical University conducted a cross-sectional study to determine the validity of a 45-item FFQ designed to assess macronutrient intake against three 24-hour dietary recalls in Taiwan, comparing fruit and vegetable consumption with carotenoid biomarkers.
They recruited 126 adults with type 2 diabetes to take the FFQ, as well as three 24-hour dietary recalls administered by a licensed dietitian. The FFQ was designed to assess the frequency of food group consumption, serving sizes, and certain eating habits over the previous six months.
Consumption frequencies of certain food groups (such as Chinese staple foods, light- or dark-coloured vegetables, fresh fruits, red or white meats, eggs, soy and dairy products, etc.) were listed as portion sizes consumed per day, week, or month.
They were then converted to weekly equivalents, and each participant's daily energy intake was estimated — dietary assessment details using this FFQ had previously been cited in studies that correlated certain dietary patterns and the risk of renal diseases and metabolic alterations in type 2 diabetes.
Diets and discrepancies
After the FFQ and 24-hour dietary recalls, 71 of the participants were randomly selected to have their plasma carotenoids — α-carotene, β-carotene and lutein — measured. The Bland–Altman method was used to examine agreement between nutrient intake values obtained via two dietary assessment tools.
The researchers then reported that the macronutrient and fibre intake values estimated using the FFQ were found to be "in high agreement with the results of (the) repeated three 24-high dietary recalls"; 71.5% to 81% of subjects were correctly classified into the same or adjacent quartiles for three macronutrients and fibres.
Furthermore, only 1.6% to 8.7% of participants were misclassified. According to the Bland-Altman plots, just 4.8% of the values fell outside the lower and upper 95% limits of agreement for fat and carbohydrates; this figure was 6.3% for protein, fibre and energy.
However, fat and fibre intakes estimated by the FFQ were found to be about 20% higher than those estimated by 24-hour dietary recalls. The researchers said this could be attributed in part to under-recording, a common occurrence in repeated 24-hour dietary recalls, or overestimation.
FFQs often overestimate nutrient and energy intakes, compared to other methods of dietary assessment. This may be linked to FFQ participants having to recall the intake frequency of a much greater number of foods than in an open-ended 24-hour dietary recall.
The high estimation of fibre intake in the study could also be due to fruit and vegetable intake over-reporting as a result of the desire for social approval, a previously reported common bias. At the same time, diabetics eager to show they are following doctor's orders to consume more nutrient-dense foods may over-report their intake of fruit and vegetables.
Nutrients and numbers
The researchers said the study was limited by the small number of participants and listed food items. In addition, they did not test the reproducibility of their FFQ data, saying that an FFQ's long-term reproducibility should be re-evaluated within a year.
The small number of carotenoids assessed as biomarkers may also have limited the confirmed consumption of fruits and vegetables.
They concluded: "Future studies should be performed using other biomarkers to confirm more nutrients or specific food groups, such as urinary urea-N for protein intakes, blood fatty acids for foods containing different classes of fats, or biomarkers for micronutrients.
"This short 45-item FFQ proved to be a valid assessment of energy, macronutrient, and fibre intake from diets usually consumed by patients with type 2 diabetes. "These findings suggest that the FFQ could potentially be used in busy clinical settings treating patients with type 2 diabetes in Asia, or diabetes patients consuming their usual diets."
Source: International Journal of Environmental Research and Public Health
"Validity of a Short Food Frequency Questionnaire Assessing Macronutrient and Fiber Intakes in Patients of Han Chinese Descent with Type 2 Diabetes"
Authors: Meng-Chuan Huang, et al.