dietary assessment

• Food and nutrition are important components of health at both at the individual and population levels
• Nutrient intake is a major factor in health and nutritional status
• Dietary intake normally includes all foods and beverages consumed via the oral cavity
• Relationship between diet and disease is examined through various study designs (observational and experimental)
• Dietary assessment


  Involves the measurement of the quantity of foods and beverages consumed by individuals and groups
• Information obtained from dietary assessment can predict possible nutrient deficiencies when used in conjunction with anthropometric, biochemical, and clinical data
• Food consumption can be assessed at the national, community, household, and individual levels, throughout various life stages
• Dietary assessment can also be applied in hospital and emergency settings
• Four Levels of Objectives in Measuring Dietary Intake

  • Mean Intake of a Group
  • Proportion at risk to Inadequate Intake
  • Rank Intakes of Subjects Within the Distribution
  • Usual Intakes for Correlations or Counseling
• Level 1: Mean Intake of a Group


  • Measure food intake of each subject for one day only
  • Ensure all days of the week are proportionately represented in final sample
• Level 1 objectives


  • To describe usual mean nutrient intake of preschool children (or any other group)
  • To demonstrate a significant difference in mean or median intakes between two groups
  • To demonstrate a significant change in group mean intakes, based on paired measurements (before and after intervention)
• Level 2: Proportion at risk to Inadequate Intake


  • Measure food intake for at least two days on sub-sample (30-40 subjects)
  • Non-consecutive days should be used when using two repeats
  • If non-consecutive days not possible, then three consecutive days are needed
• Level 2 objectives


  • To determine distribution of intakes within group to assess proportion at risk of inadequate intakes
  • To determine a significant change in proportion at risk of inadequate intakes before and after intervention
  • To determine a significant change in proportion at risk of inadequate intakes between groups
• Level 3: Rank Intakes of Subjects Within the Distribution


  • Multiple replicates of 24-hour recalls/diet records/diet history
  • Alternately, semi-quantitative FFQ can be used
• Level 3 objectives


  To assess the relationship between frequency of food groups (e.g., frequency of consumption of green leafy vegetables versus mean level of biomarker
• Level 4: Usual Intakes for Correlations or Counseling


  • Larger number of replicates required
  • Alternatively, semi-FFQ or diet history can be used
  • Replicates depends on the objective (whether correlation or ranking) and on within-subject variation
• Level 4 objectives


  To assess inter-relationship between nutrient intakes of individuals to other indices of nutritional status measured in the same persons
• Uses of dietary assessment

  • Assess the first sign of any nutritional deficiency, i.e., dietary inadequacy
  • Assess and monitor food and nutrient intake of population groups and individuals
  • Formulate and evaluate health and food/agricultural policies and programs
  • Complement epidemiologic research
  • Assist in product formulation by food industry
• Dietary assessment principles

  • Adequacy
  • Balance
  • Variety
  • Nutrient density
  • Moderation
• Adequacy


  a diet that provides enough energy and nutrients to meet the needs according to the recommended dietary intakes/allowances (for healthy and active life)
• Balance


  a diet that provides enough, but not too much of each type of food (adequacy of basic food groups)
• Variety


  a diet that includes a wide selection of foods within each food group (dietary diversity/ includes biodiversity – species, varieties, cultivars)
• Nutrient density


  • a ratio of nutrient content (in grams) to the total energy content (in kilocalories or joules); fruits and vegetables are nutrient-dense foods, while products containing added sugars, processed cereals, and alcohol are not
  • a ratio of the nutrient composition of a given food to the nutrient requirements of the human body; therefore, a nutrient-dense food is the food that delivers a complete nutritional package
  • a ratio of food energy from carbohydrate, protein or fat to the total food energy
• Moderation


  • A diet that limits intake of foods high in sugar and fat (nutrient intake goals/guidelines)
  • Not eating to the extremes, neither too much nor too little
• People do not eat the same foods every day and nutrient intake varies from day to day
• If only one day's intake is determined, the true long-term nutrient intake may be misrepresented
• Intra-individual variation


  Individual's day-to-day variation
• Inter-individual variation


  Degree to which various individuals differ from one another in their nutrient intake
• Usual food intake


  The long-term average intake of a food or nutrient or habitual daily intake
• Actual food intake


  The amount of food that one actually consume
• The concept of usual food intake is important because dietary recommendations are intended to be met over time and diet-health hypotheses are based on dietary intakes over the long term
• Policymakers want to know the proportion of the population at or below a certain level of intake
• Researchers want to examine relationships between diet and health
• Methods for Measuring Food Consumption

  • Qualitative
  • Quantitative
• Quantitative methods


  • Recalls or records designed to measure the quantity of food consumed over a one-day period
  • By increasing the number of measurement days, quantitative estimates of recent food intakes, or—for longer time periods—habitual food intake of individuals can be obtained
• Qualitative methods


  • Dietary history and FFQ
  • Used most frequently to assess habitual intake of foods or specific classes of foods rather than intakes of nutrients
  • With some modification, they can provide data on habitual nutrient intakes
• Methods of dietary assessment

  • Retrospective
  • Prospective
• Retrospective methods


  • 24 Hour food recall
  • Food frequency questionnaire
  • Diet History
• Prospective methods


  • Estimated food records
  • Weighed food records
• Choice of Methods to Assess Food Intakes of Individuals/Groups depends on the level of study objectives, validity and reproducibility of the dietary assessment method, characteristics of the target group, respondent burden, and availability of equipment and resources