12 January - 20 June 2016

Review of resistant starch health benefits published

A review of the health effects of resistant starch (RS) by researchers from the British Nutrition Foundation and University College Dublin, published in Nutrition Bulletin, has sought to summarise the reported effects of RS and mechanisms by which these are underpinned.

A review of the health effects of resistant starch (RS) by researchers from the British Nutrition Foundation and University College Dublin, published in Nutrition Bulletin, has sought to summarise the reported effects of RS and mechanisms by which these are underpinned.

The benefits of adequate dietary fibre have been well documented over many years. RS is defined as the fraction of starch that resists digestion in the small intestine and so reaches the large intestine intact. RS is therefore considered to be a type of dietary fibre. The authors of the current review, Lockyer and Nugent, note that an “array of health benefits have been attributed to RS” and seek to examine these by considering human studies published between January 2005 and July 2016.

The review notes that there are 5 types of RS, RS1- RS5, and details food sources of RS, such as bananas, pasta, pulses and potatoes. It notes that commercially purified forms are available which can be added to food products and states that RS is an “established” ingredient, used in a wide range of products as well as for “the microencapsulation of components such as probiotics”. The review briefly discusses how the challenges of developing food products with added RS are often dependant on RS type and food processing methods.  It states that RS intake in the UK is estimated to be around 3g/day and notes that there is no current official recommended intake for RS.

Lockyer and Nugent discuss studies which have investigated colorectal health benefits of RS. They indicate a number of key points including that RS increases the production of short chain fatty acids (SCFA) in the gut and that evidence suggests RS influences gut microbes which, if shown to be selective in favour of health-promoting bacteria, could lead to RS being classified as a prebiotic. The review notes that while there is no evidence that RS has any effect on colorectal cancer occurrence in those at high risk, there is to suggest a reduction in disease markers and that “RS can counteract the detrimental effect of high red meat intake on colorectal cancer risk”.

The review then discusses studies investigating RS’s role in metabolic responses and appetite regulation. While it is now accepted that the glycaemic responses to RS are lower than for digestible starches, it indicates that longer-term studies are needed to prove the benefits of consumption on blood lipids. Some studies suggest there is evidence that “RS can decrease appetite and sort-term food intake” and states this may be due to “an increase in the release of gut hormones that promote feelings of satiety, stimulated by SCFAs”.  Lockyer and Nugent indicate some studies suggest a role for RS in the treatment of chronic kidney disease but also that there is little evidence RS can help decrease adiposity.

The review highlights an EFSA approved health claim for RS using the wording “replacing digestible starch with resistant starch induces a lower blood glucose rise after a meal” that can be used for high carbohydrate baked foods where at least 14% of total starch is RS.

Concluding, Lockyer and Nugent state that many of the health benefits of RS may yet to be uncovered and list a variety of RS-related trials currently registered investigating its effects on many factors including gut health, insulin sensitivity and CVD risk markers. They note finally that much research still only relates to RS-2 and suggest that “wider evidence relating to all RS types, via the testing of whole foods” would prove useful and might lead to a recommended intake value for RS.

RSSL's Product and Ingredient Innovation Team, has considerable experience in formulating products containing prebiotics and probiotics. For more information please contact Customer Services on +44 (0) 118 918 4076 or email enquiries@rssl.com

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