Last week we we discussed how we assess or monitor the food supply, using food balance sheets to assess food available for use and consumption, as well as food purchasing and acquisition data. This week we will investigate how we measure actual food intake and consumption.
So how do we measure the diets of individuals?Measuring food intake is one of the most difficult tasks undertaken by health professionals for several reasons. Food supply is extremely variedIndividuals eat widely varying amounts and combinations from day to dayVariations exist in recipes and nutrient content of different versions of the same foodTask of recording foods in detail is time consuming and requires a lot of co-operation from respondents
There are two overarching categories under which dietary data collection methods fall, prospective and retrospective. Prospective methods investigate current intakes, so they essentially look at the ‘here and now’. These strategies include food diaries or journals, duplicate meals, and novel approaches such as photographic dietary records.Retrospective methods investigate previous, or past, dietary intakes. Retrospective diet methodologies may include 24-hour recalls (in which people are asked what they ate or drank in the last 24 hours), food frequency questionnaires, and ‘diet histories’ which may include a variety of data collection methods and aim to ascertain what people ‘usually’ eat.
Diet histories are most commonly used in clinical dietetic practice. There are multiple variations of the ‘diet history’. Undertaking a typical diet history traditionally involves a ‘usual’ 24-recall, in which participants reported on the previous days intake and whether this represents their typical diet, a checklist to jog the clients memory, and further validation through the inclusion of a 3 day food diary.
The national health survey is a 3 yearly survey of approximately 26,000 participants, and assesses a wide range of health conditions, as well as a small number of dietary intakes via short-answer questions. These include ‘how many servings of fruits or vegetables do you consume per day’ and ‘what type of milk do you usually consume’ which is used as a proxy measure for fat.The NNS 1995 was a more detailed investigation of diet undertaken among 13 858 Australians > 2 years of age who participated in the NHSConducted using 24hr recalls in the homeThis method allowed a large number of people to be included The decision was made to use this method to allow comparison with other studies (1983 & 1986 NNS(Most recent National Nutrition Survey to date
XNB151 Week 3 Measuring dietary intake
Food and Food Food Physical NutritionalSupply purchasing & Activity Status acquisition Behaviours
Food Diaries Using household measures Set time period for recording (minimum 3 days) Record all food consumed & drink over there days in diary Include a non-working day Using weights Similar recording to above but use a set procedure for weighing using scales & measuring utensils What are the advantages? What are the limitations? Musicians Daily Diet Credit: PETER MENZEL/SCIENCE PHOTO LIBRARY
Page from a food diary example http://www.srl.cam.ac.uk/epic/images/7dfd.jpg
Chemical analysis (duplicatemeals) Collection of an identical meal/food from client for analysis useful for analysing food composition Limitations expensive & time consuming impractical outside confined setting
24-hour recall (current intake) Ask individual to remember what food & drinks they have consumed in previous 24 hours or day usually performed by trained interviewer What are the advantages? What are the limitations? Tea farmers daily diet, Kenya
24-hr Recall example http://www.srl.cam.ac.uk/epic/images/7dfd.jpg
Food frequency questionnaire (current intake) Qualitative & semi-quantitative survey of: how often foods are eaten +/- how much usually self administered, can be interview general or specific FFQ What are the advantages? What are the limitations?
Diet history Assess typical intake Bakers Daily Diet, Iran Original Adaptation - 3 components1. a usual 24-hour recall usual takes away atypical errors food amounts enhanced by using food models2. a checklist3. a short (3 days) diary
Construction WorkersDiet History Daily Diet, USA An investigation of habitual intake over aspecified period of time – usually 1 mo to 1 yr 24 hour recall + variations Details on types (e.g. low fat), quantities, brands) Indicates patterns of eating Able to estimate energy, macro & micro nutrients Able to estimate food groups Can be targeted to particular nutrients e.g. carbohydrate in diabetes Administered by a trained health professional
Limitations of food intake data – diet history honesty, memory & frankness of client need highly skilled interviewer expensive & time consuming may underestimate intake Most useful information for assessment
Photographic dietary records Relatively novel method of assessing intake. Require the individual to photograph food before eating (prospective method). Any food left over is also photographed. A reference object (e.g. card, coin) is often included in the photograph. Additional information to indentify items (i.e. description) is often necessary. Analysis of records can be either manual (by dietitian or other trained person) or automatic using image analysis software. Manual analysis should include the use of aids to reduce portion size estimation error. Stand-alone camera or mobile phone with camera function can be used.Megan Rollo, QUT PhD Student
Example: recording intake using Nutricam 1. Mobile phone with Nutricam software. 2. Capturing an image of items for consumption. “At home...black coffee,one sugar... orange juice… cornflakes, reduced fat milk.” 4. Image and voice file sent to website for analysis. 3. Describing items in image (recording voice file). Megan Rollo, QUT PhD Student
How do we investigate food intakes over time?Reliable trends in food intake over time can only be established from data collected using the same survey design & food intake methodology. Can achieve this via the aid of national dietary surveys (of intakes)– to provide information on average intake of population 1995 National Nutrition National Health Survey Survey
2007 Australian National ChildrensNutrition & Physical Activity Survey More than 4000 children across Australia Collected data on food and nutrient intake, physical activity levels and physical measurements (height, weight and waist measurements) of children aged 2-16 years. 24-hr recall + follow-up survey Purpose: “to provide the information needed for public and private sectors to work together to develop targeted strategies to address a range of health concerns in children”http://www.health.gov.au/internet/main/publis hing.nsf/Content/health-pubhlth-strateg- food-monitoring.htm
2011/13 Australian Health Survey Australian Bureau of Statistics and Department of Ageing Expands upon previous surveys Involves ~ 50,000 adults and children across Australia. Will be conducted in homes Topics include demographics, risk factors, health status, medications, chronic diseases, use of health services, and nutrition and physical activity habits. Voluntary blood and urine sample
Purpose of Dietary SurveysProvide information on: Likely impact of changes to food regulation Levels of additives & contaminants in the food supply Proportion of population complying with recommendations Need for targeted population level interventions Need for, & impact of, fortification of foodsAustralian Health Survey 2011/13 Objectives assess the level and distribution of the health of populations measure the level, distribution and influence of health determinants quantify the inputs to the health system monitor and appraise health interventions increase knowledge through research and statistics evaluate the performance of the health system understand the interrelationships of all the above.
References Cont Commonwealth Scientific Industrial Research Organisation (CSIRO ) Preventative Health National Research Flagship, and the University of South Australia, 2007 Australian National Children’s Nutrition and Physical Activity Survey Main Findings, Commonwealth of Australia, Canberra.