[url=http://www.en-net.org.uk/question/1066.aspx]Here[/url] is the original post and responses on the IYCF forum.

Nicki, Firstly, it would be important to differentiate the usage and purpose of the 12 food groups to the 7 food groups. As already mentioned, the 12 food groups is used for the Household Dietary Diversity Score (HDDS) while the 7 food groups is used for Individual Dietary Diversity Score (IDDS) specifically for Infant and Young Child Feeding (IYCF). While the IDDS is used as a proxy measure of the nutritional quality of an individual’s diet, the HDDS is used as a proxy measure of the socio-economic level of the household. The differences in the list of food groups used to construct the HDDS and IDDS (e.g. for women or children) reflect these different objectives. In the HDDS 12 food group list, one can notice that there is more emphasis on the quantity of the food diversity as compared to the IDDS (e.g. 7 food groups for children). Cereals are counted separately from roots and tubers, fruits separate from vegetables, and fish separate from meat and poultry. Also, food items such as oils / fats, sugar / honey, miscellaneous items such as condiments and sauces count separately in the 12 food group list while in the 7 food group list, these three items are just dropped from the analysis (except in contexts when oil is a food group of interest when it is a vehicle of fortification or when it is naturally rich in vitamin A such as red palm oil). Again, this is consistent with the emphasis on quantity for HDDS as reflected by the 12 food groups. Recent evidence from a 10-country analysis shows a strong association between HDDS and per capita consumption and energy availability. This suggests that household dietary diversity could be a useful indicator of food security (Ruel, Marie. “Is Dietary Diversity an Indicator of Food Security or Dietary Quality? A Review of Measurement Issues and Research Needs” IFPRI FCND Discussion Paper 140, November 2002). From this perspective, it can be said that the additional items of oil / fat, sugar / honey and miscellaneous items such as condiments and sauces and the disaggregation of fruits from vegetables and cereals from roots / tubers measure more the household's ability to purchase these items separately hence potentially indicate the household's socioeconomic status / position. On the other hand, individual dietary diversity specifically the child dietary diversity based on a 7 food group dietary diversity score was shown to have an association to child nutrition status independent of socioeconomic factors which seem to point to individual dietary diversity as reflective of diet quality (Arimond, M.M. & Ruel, M.T.M., 2004. Dietary diversity is associated with child nutritional status: evidence from 11 demographic and health surveys. The Journal of nutrition, 134(10), pp.2579–2585.) I hope this helps.

Thanks to all for your contributions - it is much clearer now which tools are used in which circumstances.