Factors Associated with Iron Status in a Hutterite Population

Several factors are known to influence the absorption of dietary iron. The type of dietary iron consumed, what foods or supplements are consumed with dietary iron can all influence iron absorption. Understanding these factors can lead to better knowledge of what may or may not influence iron absorption. Obtaining accurate dietary data is important in nutrition research. Food frequency questionnaires can be used to estimate intake over a year time period, however, validation of a food frequency questionnaire against the 24 hour recall is essential for assessing the accuracy of the food frequency questionnaire. The following chapters of this dissertation present papers that have added to work in the field of iron nutrition. It will also add to the studies of the use of food frequency questionnaires in a rural setting. Factors associated with iron status of a Hutterite population, the contribution of tea to iron status in a rural female population and the validation of a food frequency questionnaire for assessment of calcium and bone related nutrient intake in rural populations are presented

Validation of a food frequency questionnaire for assessment of calcium and bone-related nutrient intake in rural populations.

OBJECTIVE: To assess the ability of a semiquantitative food frequency questionnaire (FFQ) to measure calcium and bone-related nutrient intakes in a rural South Dakota population.DESIGN: Intake estimates from FFQ were compared with four 24-hour recalls obtained quarterly during the preceding year.SUBJECTS: Convenience sample of 100 participants of the South Dakota Rural Bone Health Study were recruited, with 81 completing the FFQ.MAIN OUTCOME MEASURES: Calcium and bone-related nutrient intakes were expressed as milligrams per day, milligrams per 1,000 kcal, or quartiles.STATISTICAL ANALYSES PERFORMED: Intakes by FFQ and 24-hour recalls were compared using paired t test and quartiles were formed to examine cross-classification.RESULTS: Calcium intakes from FFQ and recalls were 1,287 and 1,141 mg/day (P=0.01), but calcium per 1,000 kcal did not differ. Calcium intake by FFQ correlated with intake by recall when expressed as milligrams per day (r=0.49, P\u3c0.001) or milligrams per 1,000 kcal (r=0.59, P\u3c0.001). Bland-Altman graphs indicated fairly good agreement between methods. Seventy-eight percent of subjects fell into the same or within one quartile category when calcium intake was expressed as milligrams per day and 83% when expressed as milligrams per 1,000 kcal. Gross misclassification occurred in 0% to 4% of the nutrients.CONCLUSIONS: Although FFQ may not be a valid indicator of an individual\u27s intake, it does adequately classify rural populations into quartiles of calcium and bone-related nutrient intakes, making it a useful tool for assessing dietary calcium and bone related intake in rural populations