L16 - dietary assessment challenges

What is low energy reporting?

people recording or reporting the food they have eaten often report low energy intakes and may be under-eating or under-reporting

What is under-reporting?

deliberate omission/underestimation of foods

What is under-eating?

process of diet reporting can make people change their eating habits

What are the ways we can identify low energy reporters?

look a energy balance and weight, use indirect calorimetry to measure O2 in and CO2 out and metabolism of carbs and fats, doubly labelled water, goldberg equation and biomarkers

What is doubly labelled water (DLW)?

uses stable isotopes of hydrogen (deuterium) and oxygen (oxygen-18), person drinks a small amount of doubly labelled water and observe how quickly they disappear from the body to estimate CO2 production

What disappears from the body first during DLW?

oxygen-18 as expelled in urine and in CO2 in breath

What are the advantages of DLW?

simple for participants and very accurate, once you know CO2 losses for time period can calculate total energy expenditure, if in energy balance then reported energy intake should = energy expenditure

What are the disadvantages of DLW?

is expensive, only produces total energy expenditure not for individual days, assumes energy balance

What are the steps for using DLW?

collect dietary data, measure energy expenditure by DLW at the same time, calculate difference

What equation can be used if not doing DLW?

Goldberg equation - allows you to determine whether reported intake is high enough to represent plausible intake for the time period measured

What are the steps for using the Goldberg equation?

collect data on energy intake, age, sex and weight, calculate estimated BMR, determine cutoff value for person with data collected in n days, low energy reporting indicated of EI:BMR_est ratio<cutoff value

What are the advantages of the Goldberg equation?

quick, easy and cheap, non-invasive, and can be done retrospectively if you have age, sex and weight information

What are the disadvantages of the goldberg equation?

not as accurate as DLW, assumes participants are in energy balance and sedentary level of activity

What to do about low energy reporters in data sets?

delete participants? sample can become biased as LERs have other characteristics and we don’t measure high energy reporters, keep participant data but reporting prevalence may be better, so minimise risk of LER and collect data to quantify it

Why are biomarkers not typically used in dietary assessment?

only biomarkers for some nutrients, are expensive and invasive as biological specimens require complete collection, transport and storage issues, generally reflect recent intake only and may be affected by disease states