Accurate Measurements of Nutritional Status are Needed to Guide Us
Underreporting of dietary intake undermines efforts to elucidate the role of nutrition (food patterns and nutrient intake) on health and disease outcomes. The most accurate tool to measure energy intake is using doubly labeled water (DLW) with isotopic tracers so total carbon dioxide production can be measured.
Using DLW data from 2 studies involving >200 adolescents, Stice and colleagues compare DLW data with food frequency questionnaire (FFQ) results and other behaviorial/self-perception measures. The mean underreporting scores for the two studies were 1,270 and 668 kcal per day. That is a lot of calories! FFQ had a weak correlation (r = 0.14) with DLW. Underreporting was more closely correlated with BMI (r=0.26 and 0.20) and sex (r=0.24, P<0.01). Although these relationships were statistically significant, the relationships aren’t very useful.
The reality is that self-reported dietary intake data does not provide a reliable measure of energy intake. Given the variability of vitamin content in different foods (think about natural/non-enriched versus fortified breads, ready-to-eat cereals, dairy and meat products), dietary intake estimates for vitamins from FFQs will be even worse.
Just as people have blood samples taken to diagnose iron deficiency, diabetes, or hyperlipidemia, and use scales to monitor energy balance and body weight, biological measures are the only accurate means to assess and monitor nutrient status of vitamins, select minerals, and omega-3 fatty acids. Biological measurements do not need to be sophisticated as those used to determine optimal serum vitamin D concentration for bone health, but knowing one’s blood vitamin D or vitamin E concentration will help individuals, and their health care professionals, know if nutrient intake is adequate to maintain the normal structure and function of the body.
Stice E, Palmrose CA, Burger KS. Elevated BMI and male sex are associated with greater underreporting of caloric intake as assessed by doubly labeled water. 2015 J Nutr doi: 10.3945/jn.115.216366
Trabulsi J, Schoeller DA. Evaluation of dietary assessment instruments against doubly labeled water, a biomarker of habitual energy intake. 2011 Am J Physiol: Endocrinol Metab 281(5):E891-E899
Schild A, Herter-Aeberli I, Fattinger K, Anderegg S, Schulze-Konig T, Vockenhuber C, Synal H-A, Bischoff-Ferrari H, Weber P, von Eckardstein A, Zimmerman MB. Oral vitamin D supplements increase serum 25-hydroxyvitamin D in postmenopausal women and reduce bone calcium flux measured by 41Ca skeletal labeling. 2015 J Nutr doi: 10.3945/jn.115.215004
McBurney MI, Yu EA, Ciappio ED, Bird JK, Eggersdorfer M, Mehta S. Suboptimal serum α-tocopherol concentrations observed among younger adults and those depending exclusively upon food sources, NHANES 2003-2006. 2015 PLoS ONE doi: 10.1371/journal.pone.0135510