May 1st, 2019, marked the official launch date for the International Dysphagia Diet Standardization Initiative (IDDSI) in the United States.
IDDSI is a global standardized way of describing foods and drinks that are safest for people with feeding, chewing, or swallowing problems.
This article serves as a beginner’s guide to the IDDSI framework with information on the IDDSI food and drink levels and testing methods.
What is the International Dysphagia Diet Standardization Initiative (IDDSI)?
IDDSI was founded with the goal of developing a globally standardized language for texture-modified foods and liquids for people with dysphagia of all ages, in all care settings, and all cultures.
Dysphagia refers to difficulty or trouble swallowing and is estimated to affect 8% of the world’s population (1).
It’s commonly associated with certain diseases such as strokes, amyotrophic lateral sclerosis (ALS), and forms of dementia such as Parkinson’s disease (2).
Although dysphagia can affect anyone irrespective of age, it’s highly prevalent among older adults living in assisted living or skilled nursing facilities, where up to 40-60% of residents are reported to have swallowing difficulties (3).
To promote safe and efficient swallowing, the texture of foods and the thickness of liquids are commonly modified.
The IDDSI framework consists of a continuum of 8 levels (0-7), where drinks are measured from levels 0-4, and foods are measured from levels 3-7 (4).
Levels are identified by text labels, numbers, and colors to improve safety and identification.
The IDDSI framework is pictured below.
Level 0 (thin)
Thin (or regular) liquids flow easily and are most often used when there are no issues with swallowing liquids.
Thin liquids include water, milk, tea, coffee, and juice.
Level 1 (slightly thick)
Slightly thick liquids are thicker than water but can still flow through a straw and are used if there is a problem swallowing thin liquids.
Some drinks may be slightly thick like some fruit nectars or milk, but other thin liquids will have to be thickened.
Level 2 (mildly thick)
Mildly (or nectar) thick liquids may be used if thin and slightly thick drinks flow too quickly to be consumed safely.
Mildly thick liquids pour quickly from a spoon but slower than slightly thick drinks and require some effort to drink through a straw.
Level 3 (moderately thick or liquidized)
Moderately (or honey) thick liquids overlap with the consistency of liquidized foods and must be smooth with no lumps, fibers, or seeds.
Moderately thick liquids and liquidized foods allow more time for the mouth to control and are best taken from a cup using a spoon.
Level 4 (extremely thick or pureed)
Extremely (or spoon) thick liquids overlap with the consistency of pureed foods and are usually eaten with a spoon. While they do not require chewing, they hold their shape on a spoon but are not sticky.
Level 5 (minced and moist)
Minced and moist foods (formally known as ground) require biting but minimal chewing. Foods should be soft, moist, and minced into pieces less than 4 mm in length by 4 mm width in size, or small enough to fit between the prongs of a fork.
Level 6 (soft and bite-sized)
Soft and bite-sized foods (formally known as advanced) require the ability to chew pieces no bigger than 1.5 cm in length by 1.5 cm width in size. This is about the width of a standard dinner fork.
The food can be mashed with the pressure from a fork but does not require a knife for cutting.
Level 7 (easy to chew and regular)
Level seven is divided into two subcategories: easy to chew and regular.
Easy-to-chew foods may be used if there is a strong enough chewing ability to break down soft and tender foods without help. These are normal, everyday foods of soft and tender texture.
Regular foods may be used if there are no problems with chewing or swallowing safely.
Transitional foods are not a level but are typically used together with levels 5-7. These foods start as one texture and change into another with moisture or temperature.
Transitional foods are often used in the developmental teaching rehabilitation of chewing skills. Wafers, potato chips, and ice cream are examples of transitional foods.
IDDSI testing methods
The IDDSI framework includes testing methods to confirm the level to which a food or drink belongs.
The flow test reliably classifies levels 0-3 based on their flow rate using a 10 mL syringe.
Here are the steps to perform the flow test:
- Remove plunger
- Cover the nozzle with a finger and fill the 10 mL syringe using another 10 mL syringe
- Concurrently release the nozzle and start the timer
- Recover the nozzle after 10 seconds
The amount of liquid remaining after 10 seconds identifies the level.
- 8-10 mL of liquid remaining indicates Level 3
- 4-8 mL of liquid remaining indicates Level 2
- 1-4 mL of liquid remaining indicates level 1
- 0 mL of liquid remaining indicates level 0
Fork drip test
The fork drip test — used for levels 3 and 4 — can be tested by assessing whether thick drinks or fluid foods flow through the prongs of a fork.
If the fluid drips slowly or in dollops through the prongs of the fork it is classified as a level 3, whereas if only a small amount flows through the fork and does not drip slowly or in dollops, it is a level 4.
Spoon tilt test
The spoon tilt test is for measuring foods in levels 4-5 and assesses the food’s stickiness and ability to hold together.
The food should hold its shape on the spoon and slide off easily when tilted.
Fork pressure test
The fork pressure assesses foods in levels 4-7 and determines whether a food’s texture is soft, firm, or hard.
To perform the test, press the fork onto the food by placing your thumb onto the bowl of the fork until the thumbnail balances noticeably to white.
Transitional food test
The transitional food test assesses whether a food fits the definition of a transitional food.
To perform the test, place 1 mL of water on the food and wait one minute. Apply fork pressure using the bowl of fork until your thumbnail blanches to white.
The food is a transitional food texture if after removing the fork pressure the food no longer looks like its original state or has melted significantly.
The IDDSI framework standardizes the language of thickened drinks and modified food textures for people with dysphagia.
The framework is a continuum of 8 levels (0-7), each with 3 identifiers to improve safety and identification.
The food and drink testing methods are reliable and valid ways to assess the level of foods and drinks.