The validation of a suitable nutrient profiling model for South Africa
Aim Nutrient profiling is defined as “the science of classifying or ranking food items according to their nutritional composition for reasons related to preventing disease and promoting health, and can be used to govern the criteria under which nutrient and/or health claims may be made”. The validation of a nutrient profiling model (NPM) is an essential part of the model development process, and is extremely important for the model to meet basic scientific criteria. This mini-dissertation investigated the content and convergent validity of a suitable NPM for South Africa. Method Content validity was tested for by comparing the NPM classification of 131 “indicator” foods with the classification of the “indicator” foods by the Food Based Dietary Guidelines (FBDGs). Convergent validity was tested for by comparing the standard ranking of a representative data set of food items (n = 128) by nutrition experts with the classification of the food items by the NPM. The questionnaire asked respondents to rank 40 foods (electronically generated from a master list of 128 foods) according to the nutritional information provided from “more healthy” to “less healthy” using a six point Likert scale. The 128 foods were selected to be representative of the South African diet. These questionnaires were sent via e-mail to all full members (n = 1105) of the Association of Dietetics in South Africa. The draft “Guiding principles and framework manual for the development or adaptation of nutrient profile models” dated 22 February 2011 (WHO, 2011), was used as a guide in the validation process of the NPM. Results The NPM showed good content validity: the way that the NPM categorises foods correspond well with that of the FBDGs (kappa statistic = 0.73). Two hundred and ninety two responses were received (26.4%) from the nutrition experts, these responses were used to rank the 128 foods by the average score which they received from the nutrition experts. The NPM also showed good convergent validity: the NPM classification of foods had a good correlation with the standard ranking of foods by dietitians (r = 0.853; p = 0.0001). Conclusion The NPM demonstrated good content validity by classifying food items in way that supports the FBDGs with the exception of a few processed food items and combined food items. The NPM also demonstrated good convergent validity by classifying food items in accordance with the views of nutrition experts in South Africa.
- Health Sciences