Nutrition and Diet Flashcards
Define ‘diet’.
The type and amount of food and drinks that a person consumes regularly.
What are individual dietary recommendations based on?
Age
* Gender
* Physiological status (such as pregnancy)
* Weight/Height
* Physical activity
* Health status etc.
What are dietary reference values (DRVs)?
A set of estimated nutrient requirements for healthy populations in the UK.
What are DRVs used for?
To inform public health policies, food labelling, and
dietary advice given by healthcare professionals.
Define Reference Nutrient Intakes (RNI).
Levels of nutrients that are sufficient to meet the needs of almost all (97.5%) individuals in the population.
Define Estimated Average Requirements (EAR).
Levels of nutrients that are estimated to meet the needs of half of the population.
Define Lower Reference Nutrient Intakes (LRNI).
Levels of nutrients that are sufficient for only a small
percentage of the population (2.5%).
Define ‘Safe Intake’.
Level of nutrients that is considered safe for most people to consume.
What are the public health reasons for measuring people’s diets?
- To evaluate/monitor the adequacy of people’s diets (nationally or locally)
- To evaluate/monitor a dietary improvement programme
What are the research reasons for measuring people’s diets?
To identify any relationships between diet and health, wellbeing or disease using large population
studies.
What are the clinical reasons for measuring people’s diets?
To help diagnose a diet-related condition.
What are the commercial/economic reasons for measuring people’s diets?
To assess consumer choice of foods
List the 2 approaches to measuring diet and nutrition.
- Measure dietary intake
- Measure nutritional status
How do you measure nutritional status ?
Using biomarkers via blood, urine etc.
What is the purpose of measuring dietary intake?
Evaluate type and quantity of foods consumed and
identify levels of nutrient intakes.
What is the purpose of measuring nutritional status?
To identify the levels of a nutrient in a person’s body.
Give an example of a direct method of measuring diet and nutrition.
Directly measure food intake by individuals (can be
households).
Give an example of an indirect method of measuring diet and nutrition.
Estimate intake by using information on food
availability (can be at national, regional or household level (not individual).
Define ‘biomarker’.
Substance found in the body that can be used to measure physiological processes and reflect changes in a person’s health status.
Give two examples of biomarkers.
- Blood levels of vitamin D
- Urine to measure sodium
Give examples of objective methods to assess dietary intakes.
Direct observation, duplicated diets (biomarkers)
Give examples of subjective methods to assess dietary intakes.
- Weighed food diaries
- 24 hour recall
- Food frequency questionnaire
List a few strengths of prospective food diaries.
- Provides detailed descriptions of all foods and drinks.
- Food / drink recorded at time of consumption, so no recall error.
- If weighed, portion sizes exact.
- All eating occasions covered.
- Good for capturing foods eaten frequently
- Excellent estimates multiple levels; for energy, nutrients, food and food groups and overall diet.
List a few weaknesses of prospective food diaries.
- Can be time consuming and labour intensive. Very costly in staff time.
- Large respondent burden - individuals must be
motivated, compliant, numerate and literate. - The individual may alter his/her diet to make it easier to record. Intake recorded may not be ‘typical’ diet.
- Weighing food eaten away from home can be difficult
- Foods eaten less than once or twice a week may not be
captured. - If 7 days, recording can become less accurate towards
the end of the period because of study fatigue.
List a few strengths of 24 hour recall method.
- Provides detailed descriptions of all foods and drinks.
- Can estimates multiple levels; for energy, nutrients, food and food groups and overall diet for a large group.
- Respondent burden is relatively low.
- Can be relatively quick.
- Recall does not alter food intake pattern but may introduce recall bias.
- Literacy not required if interviewer administered.
- Can be repeated e.g. 3 separate 24h recalls to give better idea of habitual intake
List a few weaknesses of 24 hour recall method.
- Single 24 hour recall not representative of habitual individual intake but may be useful for group means.
- Method is reliant on memory and developed cognitive skills.
- Recall bias
- Conscious: recall healthier foods, ignore unhealthy snacks
- Expensive to administer due to high interviewer burden
- Repeat 24-hour recalls increase time and cost of analysis.
List a few strengths of food frequency questionnaires.
- Assess habitual consumption over an extended period of time
- Comparatively easy to administer
- Low cost
- May be self administered via mail or phone/online.
- Can gather information on a range of foods or be shorter and focus on specific foods / nutrients.
- Portion size estimates can be used to obtain absolute nutrient intakes.
- Data can be analysed relatively quickly.
- Computer-readable forms can be scanned into computers reducing data-entry errors.
List a few weaknesses of food frequency questionnaires.
- The list can never include all foods.
- Accurate reporting relies on respondent’s memory.
- May be bias due to differential under- or over- reporting.
- Requires literacy and numeracy skills.
- Estimating portion sizes accurately can be difficult.
- May not be completed fully.
- Food list may not reflect eating habits of all sub-populationq
List a few examples of new technologies that are used for dietary assessments.
- Wearable devices
- Smartphones apps
- Digital photography
List a few advantages of new technologies that are used for dietary assessments.
- Can be used irrespective of time or location.
✓ More opportunity for real time data collection.
✓ Possibility to reduce measurement error – larger food databases or pictures to aid portion size calculations.
✓ Lower participant burden (often faster to complete).
✓ Reduced data processing – some opportunity for automated nutrient assessment.
✓ Some participants report preference for innovative techniques.
List a few disadvantages of new technologies that are used for dietary assessments.
- Recall Bias – many techniques still rely on individuals to remember their intake correctly.
- Performance Bias – Individuals are still likely to change their diet over assessment period using methods that rely on real time data collection.
- Social Desirability Bias – Individuals may misreport their intake to be more desirable.
- Measurement Error – although this can be greatly improved, there is likely to be some measurement error, and this is likely to vary between technologies.
- Have not always been validated.
Write the formula for estimated value.
Estimated Value = True Value + Total Error
What type of study design is the National Diet and Nutrition Survey (NDNS)?
Continuous cross-sectional survey
When did the NDNS begin?
Began in 1992 but became a continuous program in 2008.
What is the purpose of the NDNS?
To collect detailed information about food consumption, nutrient intake and nutritional status of the general population aged 1.5 years and older living in private households in the UK.
What was the dietary assessment method used in the NDNS?
- Up to 2008: Weighted 7-day diet diary / 24-hour recall
- Between 2008-2018: Paper based 4-day estimated diary
- 2019 onwards: online 24-hour recall (Intake24)
- Biomarkers also collected
What type of study design is the National Survey of Health and Development (NSHD)?
Longitudinal birth cohort
What kind of participants were used in the NSHD?
All participants born in the same week of 1946.
What were the dietary assessment methods used in the NSHD?
- 24-hour recall in 1950, 1982 and 1989
- 5-day estimated food diary in 1982, 1989, 1999, 2006-2009
