Basic nutritional investigation New Quantitative Index for Dietary Diversity (QUANTIDD) and its annual changes in the Japanese Kota Katanoda, Ph.D. a, *, Hee-Seon Kim, Ph.D. b , and Yasuhiro Matsumura, Ph.D. a a Division of Health Informatics and Education, National Institute of Health and Nutrition, Tokyo, Japan b Department of Food Science and Nutrition, Soonchunhyang University, Asan, Republic of Korea Manuscript received April 26, 2005; accepted June 8, 2005. Abstract Objective: A diverse diet is recommended in many dietary guidelines. However, because there are no unified standards for measurement methods, objective comparisons across different populations or time points is difficult. This report proposes a new dietary diversity index based on quantitative distribution of consumed foods to allow objective measurement of dietary diversity. Methods: A Quantitative Index for Dietary Diversity (QUANTIDD) is proposed: QUANTIDD = (1 -  j n prop[j] 2 )/(1 - 1/n), where prop(j) is the proportion of food group(s) j that contributes to total energy or nutrient intake, n is the number of food groups, and j = 1,2,. . .,n. The numerator is the probability that the two foods taken out of an aggregation of consumed foods belong to different food groups. The denominator is its maximum value. The index ranges from 0 to 1. By using the officially released average data from the National Nutrition Survey in Japan from 1957 to 2000, we investigated annual changes in the QUANTIDD. We also investigated the distribution of the index by using individual data from the National Nutrition Survey in Japan in 1996. Results: The QUANTIDD increased from the 1960s to the 1970s. This was the era of rapid economic growth in Japan, during which the dietary habits of the Japanese underwent rapid changes. The distribution of the QUANTIDD was skewed to the left, but logit-transformation decreased this asymmetry and made it similar to a normal distribution. Conclusion: Because this index can measure dietary diversity objectively and is suitable for statistical handling, it is useful as a method to compare dietary patterns across different populations or time points. © 2006 Elsevier Inc. All rights reserved. Keywords: Dietary diversity; Dietary variety; Quantitative index; National Nutrition Survey in Japan; Nutritional transition Introduction A diverse diet is recommended by many dietary guide- lines [1]. Scientific evidence that a diverse diet provides a suitable intake of required nutrients is being accumu- lated [2–5]. However, there is no unity among the in- dexes by which dietary diversity is evaluated [6]. Many previous studies have used the number of foods (food groups) consumed during a given period or some other similar measurement as an index. Because there is no uniformity as to what types of foods are counted and by what method, objective comparison across different pop- ulations or time points is difficult. Further, the number of consumed foods (food groups) is not suitable for describ- ing quantitative variations of consumed foods. Therefore, this report proposes a new index that takes into consid- eration the quantitative aspect of consumed foods for objective evaluation of dietary diversity. We applied the new index to data obtained from the National Nutrition Survey in Japan (J-NNS; although its name was changed This study was supported by 2004 DIJ Research Grant from the Danone Institute of Japan, a Grant-in-Aid for Young Scientists (B) from the Japan Society for the Promotion of Science (16790355), and a Health and Labour Sciences Research Grant for Research on Children and Fam- ilies from the Ministry of Health Labour and Welfare, Japan. * Corresponding author: Tel.: +81-3-3203-5722; fax: +81-3-3203- 5605. E-mail address: katanoda-tky@umin.ac.jp (K. Katanoda). Nutrition 22 (2006) 283–287 www.elsevier.com/locate/nut 0899-9007/06/$ – see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.nut.2005.06.014