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HUNT242 > Lecture 18: Dietary Assessment Challenges > Flashcards

Lecture 18: Dietary Assessment Challenges Flashcards

1
Q

What is low energy reporting?

A

When people report very low energy intakes
- May be under-reporting or under-eating

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2
Q

What is under-reporting?

A

Deliberate or unintentional omission or underestimation of foods

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3
Q

What is under-eating?

A

Process of diet reporting can make people change their eating habits

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4
Q

What are mean adult energy intakes (Adult Nutrition Survey 2008)?

A

Males (19-30y) = 11.9 MJ
Females (19-30y) = 8.4 MJ

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5
Q

How can we identify low energy reporters?

A

Doubly Labeled water (DLW) or Goldberg Equation

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6
Q

What is DLW error?

A

Very accurate (only 1-2% error)

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7
Q

What is energy balance?

A

Energy in = Energy out

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8
Q

What is energy in?

A

Reported energy intake

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9
Q

What is energy out?

A

Energy expenditure

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10
Q

How are carbohydrates metabolised?

A

Use 6 oxygen -> produce 6 carbon dioxide

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11
Q

How is fat metabolised?

A

Use 23 oxygen -> produce 16 carbon dioxide

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12
Q

What are both CHO and Fat equations the basis of?

A

Indirect calorimetry

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13
Q

What is indirect calorimetry?

A

Measuring oxygen going in and carbon dioxide coming out to figure out how much energy was expended and metabolised

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14
Q

What are stable isotopes used for doubly labelled water?

A

Deuterium and oxygen-18

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15
Q

What is deuterium?

A

Stable isotope of hydrogen (added neutron)

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16
Q

What is oxygen-18?

A

Stable isotope of oxygen (2 added neutrons)

17
Q

What does double labelled water estimate?

A

CO2 production without needed breathing apparatus

18
Q

How does doubly labelled water work?

A

Drink a small amount of labelled water with both isotopes on them and collect urine samples to determine how quickly isotopes disappear from the body
- Isotopes weigh a different amount so you can measure them

19
Q

What does deuterium attach to?

A

onto H2

20
Q

What does oxygen-18 attach onto?

A

Oxygen (O)

21
Q

What are advantages of DLW?

A
  • Once know CO2 losses for time period can calculate total energy expenditure
  • If in energy balance then reported energy intake should = energy expenditure
  • Very accurate
  • Relatively simple for participant
22
Q

What are disadvantages of DLW?

A
  • Very expensive
  • Only get average total energy expenditure (not for ind days)
  • Assumes energy balance
23
Q

How do we use DLW to identify LER?

A
  1. Collect dietary data
  2. Measure energy expenditure by DLW at the same time
  3. Calculate difference
24
Q

How can we identify low energy reporters when DLW is inconvenient or too expensive?

A

Equations can be used based on estimated basic energy requirements e.g. Goldberg Equation

25
Q

How does the Goldberg equation allow you to determine?

A

Whether reported intake is high enough to represent the plausible intake for the time period measured

26
Q

Why is cutoff to determine plausible intake lower than it would need to be?

A

To determine whether intake represents habitual intake - varied intake from day to day

27
Q

What are advantages to the Goldberg equation?

A
  • Quick, easy, cheap
  • Can be done retrospectively if have age, sex and weight
  • Non-invasive
28
Q

What are disadvantages of the Goldberg equation?

A
  • Not as accurate as DLW (misses some LERs)
  • Assumes participants are in energy balance
  • Assumes sedentary level PA
29
Q

What are options for dealing with low energy reporting data?

A
  • Delete participants
  • Keep participants but report prevalence
  • Collect data to quantify LER
30
Q

What are biomarkers?

A

Substances in biological specimens such as blood, urine or hair which reflect intake sufficiently closely to act as objective indices of true intake

31
Q

Why use biomarkers?

A

They are independent of many errors associated with dietary methods

32
Q

Biomarkers can be used to…

A
  • Assess measurement error
  • Calibrate measurement error in dietary data
33
Q

Why not use biomarkers instead of dietary assessment?

A
  • Only available for some nutrients
  • Often expensive
  • Invasive
  • Transport and storage issues
34
Q

How are biomarkers invasive?

A
  • Biological specimens
  • Complete collection required
  • Multiple collections may be required
35
Q

What are disadvantages to using biomarkers?

A
  • Many assumptions
  • Don’t necessarily capture total intake
  • Generally reflect recent intake only
  • May be affected by disease status
36
Q

How don’t biomarkers capture total intake?

A
  • LER’s are often under-collectors of biological samples
  • Urine nitrogen will only. show approx. 80% of intake
37
Q

What methods can be used to identify LERs?

A

Doubly labelled water or the Goldberg equation

38
Q

Biomarkers are useful adjuncts to dietary assessment but…

A

Do not replace them

39
Q

LER is not necessarily…

A

Intentional

HUNT242 (24 decks)

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