These are 3 steps in estimating an individual's intake:

  1. Collect amount of all the different foods/drinks this person takes in on an average day.
  2. Using food tables software, compute that person's intake of the different nutrients per day
  3. Compare these nutrient intakes against a reference for each nutrient, the estimated average requirement (EAR). This is lower than the recommended nutrient intake (RNI, RDI, RDA).

Methods to collect information

For step ONE there are 4 methods:

  1. 24 hour recall
      Write down everything you ate or drank yesterday and estimate the amounts of each
  2. Food intake record
      Record everything you eat or drink, and the amount for one or more days. Write it down throughout the day (don't try and remember later on, and what type of bread, what type of milk etc.).
  3. Diet history
      On a typical day what do you eat and drink. This needs prompts 'what about in the evening, watching TV', etc.
  4. Food frequency questionnaire

      Booklet with list of foods/drinks provided - usually over 100. (They have to be food groups rather than individual products, e.g. breakfast cereals). Do you usually eat: more than once a day, daily, several times a week, weekly, occasionally, rarely or never?

    5. 24 hour recall

    The 24 hour recall (method) is used usually for national nutrition surveys because the exact individual foods should be captured.

     

    Food intake record

    The food intake record (method) is a useful technique in helping overweight people modify their food habits.

     

    Diet history

    The diet history (method) is probably most used by a doctor who want to screen a patient for inadequate or unhealthy food habits.

    Food frequency questionnaire

    The food frequency questionnaire (method) is used for large epidemiological studies.

All estimates of food intake depend on the cooperation, honesty and memory of the individual and estimates of usual intake are very difficult in people with an irregular lifestyle (lots of travelling, changing shifts, etc).

When computing nutrients from the foods, the Australian nutrient databases are often based on analyses done in UK or USA, not on Australian foods. It is very difficult to be sure of the nutrients in mixed dishes because this depends on the recipe, which the consumer never knew.

The above 4 methods would usually be done by a dietitian or nutritionist, often in a research setting.

For the busy clinician

A short checklist about this patient's eating habits is a useful screening method:

An examination (clinical, anthropometric and/or biochemical) is required to confirm a diagnosis of malnutrition suggested by the food intake history.

National Food Consumption Figures

In Australia national surveys of food intakes of representative samples of people (national nutrition surveys) by the federal Department of Health happen when the government is persuaded to provide the funds. The last NNS was done in 1995/6 on over 13,000 people (range of ages, males and females, urban and rural, all States) published by the ABS and Department of Health. Another NNS is overdue! The only other one in this country was in 1944.

We also have regular annual publication of Apparent Consumption of Foodstuffs and Nutrients Australia, by the Australian Bureau of Statistics. For this, national food production plus imports minus exports is divided by the estimated population. The numbers for food and nutrient consumption are larger than individual intakes because a significant percentage is wasted or fed to tourists.

References

Truswell, A. Stewart, (2003), ABC of nutrition, 4th edn., BMJ Books/Blackwells, London.