The answer to obesity is functional

13 March 2013

We don’t need functional foods to survive, but they do provide huge health benefits, and may be instrumental in the prevention of obesity and other chronic diseases. Dr Miriam Clegg, of the Functional Food Centre, Oxford Brookes University, explains all.

There are many functional food ingredients that can increase satiety - feelings of fullness that follow a meal - and they come in a wide variety of different forms, such as proteins, fats and fibres, for example.

Not only does satiety indicate how full we are after eating, it also indicates how long a person will remain full following a meal, impacting the timing of their next meal and how much they will consume. Satiety is often confused with satiation, which refers to feelings of meal fullness and will dictate how much food is eaten in a single meal sitting. Functional food ingredients may have both satiety and satiation effects, depending on how and where they act in the body.

Why are functional food ingredients necessary?

Functional foods aren't nutritionally essential in the diet, but they do have many health benefits. They tend not to confer one single benefit to health, but multiple benefits. For example, glucans, soluble fibre found in barley, are known to increase satiety, reduce cholesterol and decrease glycaemic response. Green tea is known to increase energy expenditure and decrease cancer progression. So although functional foods aren't required by the body, the benefits associated with them may be instrumental in the prevention of chronic diseases. For this reason, continued research and investment in functional foods is necessary so that these benefits can be delivered to the consumer.

Novel functional foods

There are many functional foods for satiety available, some more unusual than others. This is a selection of slightly more fascinating examples of functional ingredients, one from each
of the three major food groups.

Baobab fruit powder: This is a pale powder that forms naturally inside the fruits of the baobab tree (Adansonia digitata). The baobab fruit is traditionally grown in Africa and is known there as the 'tree of life' due to its high levels of antioxidants, calcium, vitamin C, iron and potassium, as well as having a high level of soluble fibre. The high soluble fibre content and high antioxidant content means that the fruit may have the ability to reduce glycaemic response and increase satiety. This is one of the reasons it is consumed in Africa. Research examining the glycaemia-lowering and satiating properties of baobab is currently being undertaken in the Functional Food Centre at Oxford Brookes University - so watch this space as the story emerges. Although an abundance of baobab fruit powders are available on the market, the number of food products containing baobab fruit on the UK market is as yet quite limited.

Fatty acids: Much research has been carried out on different fatty acids, such as medium-chain fatty acids, diacyglycerols and conjugated fatty acids among others. Short-chain fatty acids (SCFAs) are an emerging area of research in relation to satiety. SCFAs can be derived from two sources: they can be generated in the large intestine from the fermentation of non-digestible carbohydrates and they are obtained directly from dietary sources. SCFAs comprise between one and seven carbon units in length. Food sources consist primarily of foods that have been fermented; for example sourdough bread, vinegar and vinegar-containing products, such as pickles, and some dairy products such as cheese, butter, crème fraîche and soured cream.

"Functional food ingredients may have both satiety and satiation effects, depending on how and where they act in the body."

Due to the volatility of SCFAs, SCFA-containing products have a distinctive odour and taste associated with them. SCFAs are believed to influence satiety via two orphan G-protein-coupled receptors, FFA2 and FFA3, believed to be activated by SCFAs. FFA2 and FFA3 are co-localised with the anorexigenic 'ileal brake' gut hormone peptide YY (PYY) in enteroendocrine L-cells. Hence SCFA solutions have been shown to significantly increase blood PYY concentration and reduce upper gastrointestinal motility. SCFA are believed to up-regulate leptin expression. Research into SCFA effects on satiety has however been mixed. One aspect that makes it difficult to study SCFAs and satiety is the fact that SCFAs have such a strong taste that this may be the factor influencing the food intake rather than the physiological effect of the SCFA itself. Research is ongoing both in terms of foods containing SCFA and foods that result in their production in the large intestine.

Protein: Research into the effect protein has on satiety has been ongoing for some time. It is well known that protein increases satiety to a greater extent than carbohydrate or fat, and high-protein meals cause greater acute appetite suppression than normal-protein meals. There is very little evidence to show which types of protein are the most satiating, due to the fact only a limited number of studies compare natural forms of proteins, and also because their use leads to standardisation problems involving the types of proteins and other macronutrients present in the foods. Among different protein types, whey proteins appear to have the most satiating effect. Consumption of whey protein leads to appetite suppression by several causes: whey proteins due to their satiety hormone release, bioactive peptides (primarily glycomacropeptide [GMP]), the release of amino acids especially branched-chain amino acids, such as L-leucine after digestion, or a combined action of all of these components. Research is ongoing into the sole effects on satiety of GMP with mixed results.

Consumer impact

The concept of functional foods worldwide is not a new one. Research into functional foods began in Japan in the early 1980s. By 1991, the Japanese Ministry for Health, Labour and Welfare established labelling regulations for Foods for Specific Health Use (FOSHU), making Japan the first country to introduce legislation. However, in Europe, functional-food recognition has been much slower. Here, applications for nutrition and health claims are submitted to the European Food Safety Authority (EFSA).

For a statement to be made that a food ingredient increases satiety, it needs to meet a 'general function' claim under Article 13.1 of the European Commission Regulation on nutrition and health claims. These refer to the role of a nutrient or substance in growth, development and body functions; psychological and behavioural functions; slimming and weight control, satiety or reduction of available energy from the diet.

With a growing number of functional foods available to the consumer, it is becoming increasingly daunting for them to know if food products offer their claimed benefits. The aim of the EFSA in regulated health claims is to make this information safe and reliable for the consumer. However, with regulations making it increasingly difficult for producers of these products to comply with and attend to, they may be put off developing beneficial functional foods for the European consumer market. The future of the European functional food market therefore hangs in the balance.

Green tea is thought to boost metabolic rates.
Dr Miriam Clegg is senior research fellow at the Functional Food Centre, Oxford Brookes University, UK.
Dairy products contain short-chain fatty acids.

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