1) WDDS uses 9 food groups whereas a more recent indicator, the Minimum Dietary Diversity for Women (MDD-W), uses 10 groups (it counts vegetables and fruits as two different groups). If you need to determine both WDDS and MDD-W, use 10 food groups and when analysing WDDS, merge "vegetable" and "fruit" groups into one group (gaining 9 groups, as required for WDDS).
2) The main difference between WDDS and MDD-W is that while WDDS shows us the extent to which the target population changed the average diversity of its diet (for example, from an average of 3.5 to 4.3 food groups), MDD-W tells us the proportion of the target population whose diet is sufficiently varied (i.e. meet the requirement of including at least 5 food groups).
3) WDDS is prone to seasonal differences. Do your best to collect baseline and endline data in the same period of a year; otherwise it is very likely that they will not be comparable. Do not collect data during the fasting periods, such as pre-Easter time or Ramadan.
4) Record food groups in the questionnaire only after all meals were listed in the Recording Meals Form – never record them straightaway as it is very likely that the number of food groups consumed will be underreported.
5) When training the data collectors, practice extensively which meals belong to which food group (allocate at least 3 hours full of examples and exercises). For example, while pumpkin flesh belongs to Vitamin A Rich Foods, pumkin leaves belong to Dark Green Leafy Vegetables (see more examples in the FAO Guidelines below). If your questionnaire includes examples of different foods per each group, adjust them to the local context.
6) Do not record foods in quantities lower than one tea spoon (for example, a small amount of fish powder added for flavouring). Do not count breast milk.
7) You can also use WDDS for measuring the dietary diversity of a very specific age group, such as adolescent girls aged 15 - 19 years.
8) Well-designed, long-term (3 years or more) projects have a chance to increase the average WDDS by 1 score; for short-term projects, an increase by 0.5 score is a realistic maximum you can achieve.