3 Things You Should Know About The National Dysphagia Diet
For years, a movement toward dietary standardization as related to dysphagia patients has stimulated considerable interest and discussion among health care providers, dietitians and speech language pathologists (SLPs). The comprehensive nature and intrinsic implications of this topic have created a wealth of suggestions and opinions from experts in the field, all with the ultimate goal of helping to effectively determine standardized dietary options that can then be further customized for each dysphagia patient.1
One approach that has garnered substantial attention is the National Dysphagia Diet (NDD). First published in 2002 by the American Dietetic Association, the NDD was designed as a first step to establish standard terminology and practice applications of dietary texture modification in dysphagia management. The NDD was developed through consensus by a panel of dietitians, SLPs, and food scientists.2 Based on data included in NDD content, there are three key categories of NDD data to consider that may help you better understand and manage dysphagic dietary options in the future.
1. NDD Diet Level Categories
The NDD diet levels were identified through a mix of science and experienced clinician consensus. This categorical approach used a method of classifying foods according to eight textural properties. Commonly served dysphagia diet foods were identified to represent each diet category across the continuum of the eight textures. According to the NDD, over 100 foods were tested with the utilization of an instrumental texture analyzer. The diet levels were expanded, with inclusion and exclusion of items at each level based on subjective comparison with the main anchor foods. As a result of this analysis four levels of semisolid/solid foods are proposed in the NDD:
- NDD Level 1: Dysphagia-Pureed (homogenous, very cohesive, pudding-like, requiring very little chewing ability)
- NDD Level 2: Dysphagia-Mechanical Altered (cohesive, moist, semisolid foods, requiring some chewing)
- NDD Level 3: Dysphagia-Advanced (soft foods that require more chewing ability).
- Regular (all foods allowed)3
Using the NDD suggested allowed/avoided foods for each diet level creates a starting point and consistency across care settings. By linking a diet level to each dysphagia patient, health care professionals and caretakers can evaluate acceptance of foods identified within that category, before further individualization for each patient’s situation.4
2. Liquid Viscosity Labeling Levels
In a similar manner to the dietary classification of foods, the NDD applies four frequently used terms to label levels of liquid viscosity (i.e., thickness or resistance-to-flow). The NDD proposed the following terms for liquids and correlating viscosity ranges:
- Thin: 1-50 centiPoise (cP)
- Nectar-like: 51-350 cP
- Honey-like: 351-1,750 cP
- Spoon-thick: >1,750 cP 5
Regarding these categories, the NDD task force acknowledges that that these ranges are “a commonsense approach” and “a catalyst for more research.”6 Research has demonstrated that clinicians, including speech-language pathologists (SLPs), show significant variation in the amount of thickening powder they feel is necessary to mix a liquid to “nectar-thick” or “honey-thick” consistency.7 Since the publication of the NDD; research has expanded to study liquid viscosity in the context of type of thickener, bolus size and specific medical conditions.8, 9
3. Analysis of the National Dysphagia Diet – Where do we go from Here?
The NDD authors stressed that the categorization process is a work in progress and far from a perfect science, especially as applied to the individualized needs of each dysphagia patient. While establishing liquid and food-related categorical protocols may help to create a standardized “starting point” to evaluate the specific needs of each patient, both the NDD task force and ASHA experts acknowledge that there is much research to be conducted and it should never be applied as a “one-size-fits-all” approach. As the NDD states, “Further study and peer-reviewed, scientific data will be needed to truly quantify the management parameters surrounding the complex diagnosis of dysphagia.”10
The International Dysphagia Diet Standardization Initiative (IDDSI) work group has taken up the challenge to relook at the dysphagia diet from a global perspective. They are a group of people from diverse professions including nutrition & dietetics, medicine, speech pathology, occupational therapy, nursing, patient safety, engineering, food science & technology from around the world who have come together to establish an international standardized terminology and definitions for texture modified foods and thickened liquids for persons with dysphagia. In the next several years clinicians just might see the next evolution of a NDD.11
- National Dysphagia Diet Task Force (2002). National Dysphagia Diet: Standardization for Optimal Care. Chicago, IL: American Dietetic Association.
- O`Neil, K. H., Purdy, M., Falk, J. & Gallo, L. (1999): The Dysphagia Outcome and Severity Scale. Dysphagia, 14, 139-145.
- Cichero, J. A., Jackson, O., Halley, P. J., & Murdoch, B. E. (2000). How thick is thick? Multicenter study of the rheological and material property characteristics of mealtime fluids and videofluoroscopy fluids. Dysphagia, 15, 188-200.
- Glassburn, D. L., & Deem, J. F. (1998). Thickener viscosity in dysphagia management: variability among speech-language pathologists. Dysphagia, 13, 218-222.
- Steele, C. M., Van Lieshout, P. H. H. M., & Goff, H. D. (2003). The flow properties of liquids: How do clinicians’ interpretations of labeled consistency compare with objective rheological measurement? Dysphagia, 18(2), 1-14.
- Clave P, et al. (2004) Approaching oropharyngeal Dysphagia. Rev Esp Enferm Dig 96,119-131.
- Robbins J et al. (2008) Comparison of 2 interventions for liquid aspiration on pneumonia incidence. Ann Intern Med 148, 509-518.
- International Dysphagia Diet Standardization Initiative (IDDSI) accessed on-line at www.ISSDI.fatcow.com