Clever Diets: Smart ingredients that change their structure could fight obesity

According to the World Health Organisation, worldwide obesity has nearly doubled since 1980 and this growing health problem is affecting millions of adults and children. In 2008, over around 1.4 billion adults were classified as overweight – including 500 million obese adults- and the problem is increasing. Childhood obesity is now considered one of the most serious public health challenges with more than 42 million children under the age of five reportedly overweight.

Obesity is preventable, but in this modern age where a high rate of food intake involves the consumption of soft, textured foods, which can be high in fat and sugars, the feeling of being full and satisfied after eating is become more and more unobtainable. One way of preventing people from becoming overweight is to reduce snacking between meals, but how is this possible if people are feeling less satisfied by what they eat?

Research and development by chemical engineers show that it is possible to develop ingredients that change their structure once in the stomach. This has recently been proven by a research team at the UK’s University of Birmingham,who have been able to manipulate the control of gel formation inside the stomach.

The research has been carried out over the last three years as part of research fellow Jenni Bradbeer’s PhD project and was funded by the BBSRC (Biotechnology and Biological Sciences Research Council). The results have been published in research paper,Food Hydrocolloids (authored by Bradbeer), and shows, through the use of gellan gum (a food ingredient found in sweets and soft drinks), that factors such as bulk and texture could be changed once in contact with stomach acid to create a greater feeling of fullness and satisfaction after eating.

Frances Marcellin: What kind of impact could this research have on obesity in the future?

Jenni Bradbeer: Reinforcing the idea of three square meals a day appears to be one of many potential routes to trying to overcome obesity within the population. If the urge to snack between meals can be reduced or eliminated using this approach, then the calorie intake, especially in the form of high fat or sugar products, can be reduced. Achieving this would have profound consequences for the individuals but also to the nations as a reduction in obesity levels nationally will have a profound and positive knock-on effect to the NHS.The self-structuring materials could be delivered in existing liquid or soft solid food products (such as porridge, soups, energy drinks and meal replacement drinks) without an adverse effect on consumer response.

FM: Why and how are certain ingredients able to alter their structure once digested?

JB: The systems investigated incorporate hydrocolloids (colloid systems wherein the colloid particles are hydrophilic polymers dispersed in water), which are derived mainly from natural sources (seaweed, agar, carrageenan, gellan), cellulose derivatives (alginate, starch), citrus peel (pectin), protein hydrolysis of bovine and fish origins (gelatin) and are used in existing foods to influence texture or viscosity.

The hydrocolloids used are acid-sensitive and respond to the pH conditions experienced inside the stomach. Once in contact with low pH conditions these hydrocolloids self-structure to form gels,gelling the stomach’s food contents also.

The gel mass and its interaction with stomach gastric motility would then give the consumer a sense of fullness, prolonging satiety and helping the consumer to resist the desire to snack.

FM: How would the gels be designed?

JB: The gels would be designed so that subsequent gel destructuring occurs naturally (through acid breakdown and gastric mechanical damage), so that the need or desire to re-eat can re-exert itself appropriately.This approach will prevent the stomach from emptying its contents too quickly, and reinforce good eating habits such as eating three square meals a day.

FM: Why were low acyl and high acyl gellan gums chosen for this study?

JB: Previous studies have investigated the ability of alginate to structure the stomach contents (Hoad et al., 2004; Norton, Frith &Ablett, 2006). These studies showed that some structuring occurred within the stomachand that satiation was prolonged as a result.

Gellan gum was thus chosen as an alternative hydrocolloid that forms acid gels. Acid gelation of low acyl gellan gum systems by direct addition of acid was first investigated by my co-workers (Norton, Cox &Spyropoulos, 2011). Using mixed gellan systems of low acyl and high acyl gellan gum was a natural progression of this work to see if the gelling kinetics could be controlled to a greater extent, preventing structuring occurring too quickly.

FM: Can you explain what analyses the gels went through during this research?

JB: The aim of the work focused on investigating the acid gelation of gellan in order to gain an insight into the gel structures that could be produced by the direct addition of acid, as well as investigating the effect of mixing the two variants of gellan to control the mechanical properties of the acid gel.

The structure of the produced acidified mixed gels were studied by means of texture analysis (via compression tests) to assess their hardness (rigidity and brittleness, and so on) and deformation properties, which could be translated to their deformation in the stomach and levels of fullness based on how hard the gel mass to be formed is.

Rheology and dynamic scanning calorimetry techniques were also used and the mixed gellan gels were also assessed post-production in terms of their response to a prolonged exposure to an acidic environment (HClacid bath) that simulated the conditions found in the stomach after ingestion.

FM: What is the next step to proving that this can actually occur from within the human body?

JB: With this approach, simple filling of the stomach with gel is not enough to provide a complete solution to the difficult problem of self-structuring foods with slow burn for control of satiety. The use of gel alone is more than capable of providing prolonged satiety but leads to unpleasant sensations for the consumer if there is no delivery of energy to the body to compliment the sensation of satiety.

A key next step to this project (currently in progress) is to look at ways to encapsulate either sugars or starches that can be slowly released and metabolised and provide a satisfactory, but low, level of nutrition and maintain consumer contentment over time.

A new collaboration with my co-workers (Jennifer Norton, Tom Mills, Department of Chemical Engineering, University of Birmingham) and Gareth Wallis (Lecturer in Sport and Health Nutrition, Department of Sports and Exercise Sciences, University of Birmingham) is currently in action, where they are looking at translating this concept into effects in people.

In terms of this context of energy release, they have some promising data involving human volunteers consuming self-structuring beverages with glucose and measuring blood glucose release through the collection of blood samples. Questionnaires were also administered to subjectively measure appetite and product acceptability.

Obviously the satiety issue is less clear in people, so at this stage we are keeping this theoretical until we investigate further under optimal study conditions.

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