With the ever-growing interest in gut health, consumers are becoming more astute when it comes to meeting their microbiome needs and are actively seeking out products and ingredients that may help them achieve the holy grail of optimal digestive health. Prebiotics are riding this wave of high interest in gut health, and whilst these gut-feeding fibres are poorly understood, the market is not showing any signs of abating, with a forecasted value of more than 64 billion dollars by 2022.1
Prebiotics are a fairly new term in the area of nutrition science, having been first discovered and named in 1995. 2.3 In 2016, following growing interest and as a result of research suggesting that prebiotics could impact microorganisms outside of the colon, the International Scientific Association for Probiotics and Prebiotics (ISAPP) produced the following definition of prebiotics “a substrate that is selectively used by a host microorganism to produce a benefit”. Put another way, Prebiotics act as a fuel to enhance the growth or activity of beneficial bacteria in the digestive system such as Bifidobacteria and Lactobacillus to improve health.
There are a number of different types of prebiotics, including fermentable carbohydrates, enodegenous prebiotics (e.g. breast milk) and exogenous food sources. With every food marketer wanting to make sure they stay on top of the wave of gut health popularity, we are seeing more and more functional foods containing prebiotic ingredients. Despite many products being touted to offer gut-health prebiotic benefits, often the actual prebiotic content is so low that it would make it difficult to consume enough to gain any real benefit. This does not necessarily deter the health-conscious consumer’s willingness to spend more on functional food products with the promise of prebiotic ingredients.
Resistant starch – the leader of the pack
The exogenous food sources of prebiotics are numerous (think whole grains, artichokes, garlic, leek, Jerusalem artichokes, legumes and green bananas). These foods are often associated with one of the more well-known prebiotics, being resistant starch. Resistant starch is the most common fermentable fibre that is talked about, partly because there is a good body of evidence to show that eating foods containing resistant starch can lead to positive changes in the gut and could protect against the genetic damage that precedes bowel cancer. In fact, resistant starch has become so sought after, that one can now purchase this specific prebiotic as a functional food supplement.
Beyond Resistant Starch
There are a number of other fermentable prebiotic fibres found in food, yet many of these don’t get the same media attention as does resistant starch.
The other common dietary prebiotic fibres include inulin, fructo-oligosaccharides (fructans, FOS), galacto-oligosaccharides (GOS), arabinoxylans and beta glucan. Whilst many consumers will be aware of these fibre types and the associated benefits, not many would group classify these as prebiotics. Therefore, as consumers become more aware that the type of fibre as well as the amount is important to achieve overall gut health, it is necessary for health professionals to educate and communicate the other often-forgotten types of prebiotic fibres, rather than allowing a single fibre (i.e. resistant starch) to become the focus.
Different foods contain varying amounts of these other types of prebiotic fibres. The BARLEYmax® grain is unique in that it contains quite a few of these prebiotic fibres, including fructans, resistant starch, beta-glucan, arabinoxylans and neutral non-starch polysaccharides.
Fructans, the less known, yet very important prebiotic fibre
It is actually fructans (not resistant starch) that have received the most research attention regarding their beneficial health effects in humans, particularly in the area of digestive health.
Fructans are polymers of fructose and serve as the naturally occurring storage carbohydrates of a variety of foods including onions and garlic, cereals including barley and wheat, agave, artichokes, asparagus and leeks.
Fructans are selective substrates for probiotic bacteria in stimulating probiotic bacterial growth, which can confer health benefits to the host through several mechanisms, including immunomodulation 4,5. Dietary fibre, of which fructans are a component, has well-known beneficial effects on human regularity (laxation), increasing faecal weight and transit time. 6 Both faecal weight and transit time are key indicators of intestinal and digestive health. 7
Fructans escape digestion in the small intestine because digestive enzymes are unable to hydrolyse the β-linked fructose units. In the colon, fructans are rapidly fermented by specific bacterial species, particularly Bifidobacteria and Lactobacillus. These aforementioned bacteria are preferentially stimulated to grow, thus causing significant changes in the composition of the gut microbiota by increasing the proportion of health-promoting bacteria or reducing the number of potentially harmful species. Fructans may also act as scavengers of reactive oxygen species, thereby decreasing inflammation.
So should we recommend greater consumption of fructans?
Ironically, whilst there has been a rise in consumer interest and desire to eat more prebiotics, at the same time we have also seen a rise in the uptake of the low FODMAP diet. Fructans, are one of the key dietary components that need to be avoided when commencing a low FODMAP diet. A low FODMAP diet can certainly be beneficial for reducing symptoms of IBS, but reduction of potential prebiotic and fermentative effects has been shown to adversely affect the colonic microenvironment. 8
The low FODMAP diet is not meant to be for life. It is actually a relatively short period of total elimination, after which FODMAP groups are systematically reintroduced, using carefully selected foods and doses. In a recent post, dietitian Marnie Nitschke talks about how whole grain foods containing FODMAPS can be re-introduced when following a low FODMAP diet.
Fructans are certainly a novel food ingredient with prebiotic and immunomodulatory properties. Fructans and their fermentation products (short chain fatty acids and hydrogen gas) can lead to a modulation of the immune system, aiming at disease prevention. Evidence is also emerging that fructans may alleviate inflammatory symptoms in diseased subjects. So when it comes to prebiotics, resistant starch needs to move out of the limelight, so that we can give these all-important fructans a chance to shine on the gut health stage.
Yours in good health,
Teri Lichtenstein APD
The Healthy Grain Nutrition Ambassador
- Hutkins RW; Krumbeck JA; Bindels LB; Cani PD; Fahey G Jr.; Goh YJ; Hamaker B; Martens EC; Mills DA; Rastal RA; Vaughan E; Sanders ME (2016).“Prebiotics: why definitions matter”. Curr Opin Biotechnol. 37: 1–7. doi:1016/j.copbio.2015.09.001. PMC 4744122. PMID 26431716.
- Gibson GR, Roberfroid MB (Jun 1995). “Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics”. Nutr. 125 (6): 1401–1412. doi:10.1093/jn/125.6.1401. PMID 7782892.
- Roberfroid MB. Inulin-type fructans: functional food ingredients. J Nutr 2007;137:2493s-502s.
- Franco-Robles E, López MG. Implication of Fructans in Health: Immunomodulatory and Antioxidant Mechanisms. Sci World J 2015;2015:289267.
- Food Standards Australia New Zealand. Standard 1.2.8 – Australia New Zealand Food Standards Code. Available from: http://www.foodstandards.gov.au/code/Pages/default.aspx
- de Vries J, Miller PE, Verbeke K. Effects of cereal fiber on bowel function: A systematic review of intervention trials. World J Gastroenterol 2015;21:8952-63.
- Halmos EP, et al. Diets that differ in their FODMAP content alter the colonic luminal microenvironment