FROM THE WDDS TO THE MDD-W: GET TO KNOW THE NEW INDICATOR FOR MEASURING WOMEN’S DIETARY DIVERSITY

As FANTA notes, “One of the most important factors responsible for maternal micronutrient deficiency is poor diets lacking diversity; however, accurate information on women’s diets and micronutrient intake is lacking.” In July 2014, a meeting of academics, international research institutes, and UN and donor agencies unanimously endorsed a new global dietary diversity indicator for assessing the quality of women’s diets. This new indicator, the Minimum Dietary Diversity-Women (MDD-W), replaces the Women’s Dietary Diversity Score (WDDS) as the standard for assessing women’s diets. In this month’s blogpost, A4NH interviews Dr. Marie Ruel, director of the International Food Policy Research Institute's Poverty, Health, and Nutrition Division about the new MDD-W.

Smiling mother with child waiting for nutrition course in Cambodia. Photo: Yifei Liu. Source: Flickr (IFPRI Images)

A4NH: Why was there a need for the new Minimum Dietary Diversity Indicator for Women (MDD-W)?

Dr. Marie Ruel: A team of researchers and development practitioners had previously worked on developing and validating an indicator of dietary diversity for women. The goal was to identify a simple proxy indicator that could help assess women’s dietary quality. Dietary diversity is one of several dimensions of dietary quality – more diverse diets are associated with greater nutrient intakes and are thus important to help individuals meet their daily nutrient requirements, a key component of dietary quality.

The result of this work led to an indicator called the Women’s Dietary Diversity Score (WDDS), which includes 9 food groups and was found to be strongly associated with micronutrient adequacy for 11 micronutrients (Arimond et al 2010; FAO 2013).

This work was a major step because for the first time, it equipped us with a simple, yet valid, indicator to assess the quality of women’s diets. Other indicators such as those that measure the intake or probability of adequacy of intake of different micronutrients require costly and time-consuming detailed 24-hour recalls, which are not feasible in large data collection exercises or for use by non-governmental institutions or other program implementers to track progress.

While useful, the WDDS had one major drawback: it failed to identify a single, universal cut-off point that would allow us to accurately classify women into those with low dietary diversity (who would be highly unlikely to meet their micronutrient requirements) and those with minimum dietary diversity (who would be more likely to meet their micronutrient requirements) across different contexts. The indicator was to be used as a continuous variable (ranging from 0-9 food groups consumed) and averaged to generate a mean value for populations. It did not allow for example to assess the percentage of the population with low or adequate dietary diversity.

For this reason, and because new data sets had become available, the team expanded the original analysis to test and validate alternative dietary diversity indicators new data sets from a variety of countries. The result of this analysis, which was followed by a consensus meeting convened by FANTA/FHI360 and FAO, was the development of the Minimum Dietary Diversity in Women (MDD-W) indicator in 2014 (FANTA 2014).

A4NH: How is this indicator different from previous indicators or measurements used?

MR: The new indicator (the MDD-W) is slightly different from the previous indicator, WDDS. WDDS had 9 food groups and the MDD-W has 10 food groups. The differences between the two indicators are: 1) in the 9-food group indicator, non-vitamin A-rich vegetables and fruits were combined and they are now separated (vegetables and fruits are now 2 different categories) in the MDD-W; similarly, beans/peas and nuts and seeds were combined in the previous indicator and they are now separated in the MDD-W; and organ meats were separated from other flesh food in the first index, whereas they are now combined in the MDD-W.

The main difference between the two indicators, however, is the fact that the new indicator has identified 5 out of the total of 10 food groups as indicating minimum dietary diversity across contexts, and < 5 groups as indicating low dietary diversity. This means that data can now be reported as percentages (or prevalences) – such as the percentage of women in a given population that do not consume minimum dietary diversity (corresponding to the % who reported having consumed less than 5 out of 10 food groups in the previous day).

A4NH: What does the WDD tell us about women’s nutrition? What does it NOT tell us?

MR: The MDD-W is an indicator that should be used at the population level – the level at which it has been validated. This means that the indicator can be used, as noted above, to derive information on the percentage of the population of women with minimum dietary diversity or their mean dietary diversity, but it should not be used to identify (or screen) individual women who are at risk of low micronutrient adequacy. At the population level, the indicator is a good “proxy” for predicting micronutrient adequacy, but it does not perform well to predict micronutrient adequacy in individual women.

Also, the indicator is derived from data on the number of food groups consumed by a woman in the day prior to the survey, but it does not include any information on amounts consumed. So, the indicator cannot distinguish between women who consumed small amounts (say for dairy, they report having consumed milk, but the amount is only 1 teaspoon added to tea) and those who consumed an average amount (say, they drank one cup of milk).

There are ways to get around this problem by making sure that enumerators are trained to do some checks on foods/food groups that are frequently used in small quantities in a given population – to add flavor or are used as a condiment. As for all data based on recall, there is also a possible memory bias, whereby women do not accurately recall and therefore misreport the food groups they consumed during the previous day (they may report more or less groups than they actually consumed).

So, as with all “proxy indicators” the MDD-W is not a gold standard or a perfect indicator, but the extensive validation studies confirmed that it was a strong predictor of micronutrient adequacy at the population level in all the data sets (from a variety of contexts) that were examined. This, therefore, makes the MDD-W a very solid indicator that we can confidently recommend for widespread use.

A4NH: What are some interesting applications of the new MDD-W indicator?

MR: The MDD-W is a useful tool to characterize and compare the dietary diversity of different populations, and for this reason can be useful to identify and target at-risk populations. The indicator can also be used to track progress and measure impact of programs and policies. It has the advantage that it can be used in large surveys – including nationally representative surveys – because it is relatively simple to use and adds only a modest number of questions to long surveys.

We have seen a lot more researchers, program implementers and large data collection systems measure dietary diversity since the first child and women dietary diversity indicators were developed, and this trend is likely to continue with the new MDD-W which provides even more useful information than the previous women’s dietary diversity indicator (e.g. the dichotomous variable which identifies the percentage of the population with low versus minimum dietary diversity).

A4NH: Are there additional updates you can envision to the indicator in the next 5-10 years, or do you think it will remain the same?

MR: I don’t foresee additional changes or validations of the indicator. It is possible, though, that although the indicator was developed and validated with data on women of reproductive age, it may end up being used more generally for other household members (e.g. adolescent girls, men, etc.). It is hard to tell how the indicator will perform with these other age groups because it has not been tested or validated for this purpose. So, I would not stop people from using it with other age groups, but they should recognize the caveat that the indicator has not been validated for this purpose.

Further reading on the new indicator: Minimum Dietary Diversity – Women

• FANTA: New Dietary Indicator to Measure Women’s Dietary Diversity
• Introducing the Minimum Dietary Diversity: Women (MDD-W) Global Dietary Diversity Indicator for Women. FANTA 2014.
• Leroy JL, Ruel M, Frongillo EA, Harris J, Ballard TJ. Measuring the food access dimension of food security: a critical review and mapping of indicators. Food Nutrition Bulletin 2015; 36(2):167-95.
• Ruel M, Ballard TJ, Deitchler M. Measuring and tracking the access dimension of food security: available indicators and recommendations for future investments. Global Nutrition Report, Technical Note 6.

Background on the old indicator: Women’s Dietary Diversity Score (WDDS)

• Arimond M, Wiesmann D, Becquey E, Carriquiry A, Daniels MC, Deitchler M, Fanou-fogny N, Joseph ML, Kennedy G, Martin-Prevel Y. Simple food group diversity indicators predict micronutrient adequacy of women’s diets in 5 diverse, resource-poor settings. J Nutr 2010; 140:2059S-69 S.
• FAO 2013. Guidelines for measuring household and individual dietary diversity.

This post is part of a blog, the Gender-Nutrition Idea Exchange, maintained by the CRP on Agriculture for Nutrition and Health. To add your comments below, please register with Disqus or log-in using your Facebook, Twitter, or Google accounts. You must be signed-in or registered in order to leave a comment.