Case Study: Measuring texture to prevent choking

Dr Ben Hanson's work to create mechanical tests to form a set of international standards to define the texture of food and drink.

Some people find it difficult to physically eat or drink – a condition known as dysphagia. It is a common problem among those who are recovering from a stroke, as well as those suffering from Alzheimer’s disease, Parkinson’s disease, cerebral palsy and certain cancers. It can also affect babies as they learn how to drink milk. To help people affected by dysphagia, it is necessary to know about the thickness and texture of the food and drink they are trying to consume. However, there were previously no international standards to define this.

In response to this issue, Dr Ben Hanson from UCL Mechanical Engineering worked with the International Dysphagia Diet Standardisation Initiative (IDDSI), to explore practical ways of measuring the softness of food and the thickness of liquids. Image shows a wrap that has been modified to have different textures, ranging from 'regular' on the left to 'Level 3 Liquidised' on the right.

Defining the texture of food and drink

“I've always loved food and drink, but I was never aware that some people had challenges with the mechanics of that,” says Dr Hanson. “It’s just one of those things that you take for granted, like walking. But it's actually a really complicated process to swallow anything.” He explains that there are 26 pairs of muscles that are involved in taking a sip of drink: “in moving, holding it as a little pool on your tongue and then squeezing and propelling that pool of water back.” Dr Hanson first became aware of the difficulties some people have with swallowing at a biomedical conference in 2005, which led him towards his research to define the texture and thickness of food and drink.

Having created a device to measure thickness for an entirely different piece of research, Dr Hanson thought he could add something to the field of dysphagia. He went on to collaborate with an international and interdisciplinary team through IDDSI. The group includes doctors, a physiotherapist, speech and language therapists, dietitians, a food scientist and Dr Hanson as the engineer. 

Although the group could access and use numerous machines to measure texture and thickness in UCL’s labs, they needed to create a solution that could be used in kitchens and on hospital wards. “The engineering part was a challenge to create scientific, mechanical tests that anybody could do in the real world,” Dr Hanson explains. “We came up with a fluid flow test using a small plastic syringe, which is internationally standardised and very low cost, as well as food tests which use standard cutlery items – forks and spoons!”

Making a difference to people suffering from dysphagia

Prior to Dr Hanson’s research, the terminology around the texture and thickness of food and drink was vague and misleading. For example, soup would be defined as being “honey thick” or food would be defined as “soft”. This type of classification was not adequate for patients with dysphagia, resulting in people not being able to consume enough, or risking death through choking.

The new IDDSI standards created by Dr Hanson and his colleagues through this research have standardised the way different foods and drinks are referred to. “It's a sort of handbook of set levels for the thickness of drinks, sauces, smoothies and soups, and for the softness of foods,” explains Dr Hanson. “The whole thing is a spectrum, from water on one side to hard, crunchy and large pieces of food on the other side. We defined all those levels.”

The standards have been adopted by countries around the world, by both professional bodies and the food and drink industry. In the UK, the standards have been formally adopted by the NHS, the Royal College of GPs, the Royal College of Speech and Language Therapists and the British Dietetic Association. In the USA, the standards have been adopted by the medical professional bodies, and in Israel, it has been mandated by law.

“The international community can communicate with one language to benefit people with swallowing disorders, or dysphagia,” Dr Hanson says. “Different products around the world are now standardised to each other, and patient diagnoses and treatments are much more precise.”

The IDDSI standards are being regularly communicated in webinars and conferences, including the European Society for Swallowing Disorders, and the IDDSI Festival taking place in September 2022, which will be attended by clinicians, the food industry, scientists and patients.

Dr Hanson hopes there will be fewer incidents of choking and infection due to food and drink going into the lungs. “That happens quite often,” Dr Hanson says, “but it becomes a problem if you don’t have the strength to cough and clear your lungs, or if you have a reduced immune system.” He says the IDDSI standards should mean there are “fewer cases of pneumonia and choking, but also greater enjoyment of food and society.”