Diverse Diet for a Healthy Microbiome


Different fibres support the growth of different species of bacteria therefore ingesting a wide variety of prebiotic fibres will support many species and strains of bacteria.  At present, there are approximately 300 species of bacteria identified in the colon of healthy western populations and 400-500 species identified in the colon of non-western healthy populations.  Why the greater amount of species in non-western populations you ask? It could largely be to do with their wider intake of prebiotic fibres.


What do I mean by prebiotic? A prebiotic is a fermentable portion of a carbohydrate.  Meaning that the sugars are accessible and a source of food for beneficial gut bacteria which in turn produce short chain fatty acids (SCFA) that are of benefit to the host aka you and me.  SCFA’s have multiple roles in the body including ordering the death of unhealthy colon cells, increasing cell division of healthy colon cells, regulating the immune system, playing a role in the metabolism of fats, improving the body’s metabolic rate and being a source of food for the cells of the colon, heart, brain and muscles.


There are different classifications of fermentable fibres such as fructo-oligosacchardies (FOS), galacto-oligosaccharides (GOS), resistant starch, gums, pectins and several more soluble fibres.


Diets high in prebiotic fibres offer protection from many chronic diseases including metabolic syndrome, diabetes, colon cancer and irritable bowel disease (IBD) by supporting your beneficial bacteria.  In fact there is a correlation between high fermentable fibre intake and lower levels of inflammation associated with metabolic, immune and gastrointestinal conditions.  Ancestral hunter-gatherer populations are proposed to consume approximately 70-120gm of fermentable fibres daily.  Western diets have been reported to average out at 10-20gm with a large percentage of the western population being closer to the 10gm.  Due to the lack of fermentable fibres in the western diet, fermentation of the fibres decreases as it moves around the colon.  This results in the bacteria switching to fermenting proteins (as they are trying to survive) producing different compounds that are toxic to cells, DNA and increase the risk of developing cancer or eating more of the mucin that makes up the protective mucosal lining.  In comparison populations that consume high levels of fermentable fibres have high levels of beneficial SCFA’s found in their stools therefore having a healthy colon, immune system and less systemic inflammation.


Beneficial bacteria species Bifidobacterium numbers was increased with prebiotic supplementation using FOS, resistant-based starch, glucose based soluble fibre and GOS.  A combination of FOS and GOS fibres were given during the first 6 months to babies with hereditary atopy and they had fewer allergic manifestations during the first 2 years of life.


Fibre from beans has demonstrated an increase in Bifidobacteria and Actinobacteria species including Fecalibacterium prausnitzii.  F.prausnitzii, a butyrate producing bacteria, has been found in low concentrations in metabolic conditions such as diabetes and obesity and chronic immune conditions such as Ulcerative colitis and Crohn’s disease.  Fibre from fruits, vegetables and beans lead to increases in beneficial Clostridia and Actinobacteria species.


FOS fibres are fermented at different rates depending on the composition of the fibre.  Examples of food high in FOS are onions, chickpeas, watermelon, asparagus, sugar beet, Jerusalem artichoke, wheat, yacon syrup, honey and banana.


Fifteen grams of FOS supplementation daily reduced levels of inflammatory proteins and increased anti-inflammatory proteins in patients with active Crohn’s disease.


Supplementation with inulin, a type of FOS found in garlic, onions, leeks and chicory root, increased F.prausnitzii and several species of Bifidobacterium including bifidum, longum and adolescentis.  Supplementation with B.adolescentis in rats reduced body fat and increased insulin sensitivity.


Resistant starch e.g.  cooked and cooled tubers (potatoes), squashes, beetroot, turnip and parsnip, cooked and cooled legumes e.g.  chickpeas and lentils has demonstrated an ability to increase numbers of beneficial Bacteroidetes and Actinobacteria species.  Resistant starch when combined with probiotic supplementation reduced the incidence of colon cancer.


Arabinogalactans is a complex fibre that is found in the cell wall of carrots, radishes, pears, corn, maize, sorghum, black gram beans and fresh turmeric.  Supplementation with larch arabinogalactabn resulted in an increase in Lactobaccilus and Bifidobacterium species.  Arabinogalactan and acemanan, the fibre found in aloe vera leaves, increased species belonging to the bacteroidetes phyla, which are found to be low in obese subjects.


Acacia gum from the Senegal Acacia tree is a complex polysaccharide meaning it is not able to be broken down in the small intestine and it is reported that 95 percent of its fibre content is fermented by the bacteria in the large intestine.  Acacia gum is fermented at a slower rate than FOS making it better tolerated.  In fact, compared with FOS, when administered for 10-15 days at a dosage less than 30gms/day it did not cause any cramping or loose stools that were associated with the FOS supplement at the same dosage.


Acacia gum contains high levels of galacto-oligosaccharides (also found in mother’s milk) in addition to other fibres.   Lactic acid producing bacteria such as Lactobacillus species where also increased with the resulting fermentation of Acacia gum producing a lower pH in the colon supporting additional beneficial bacterial species.  Certain species of Lactobacillus have demonstrated anticarcinogenic properties.


Acacia gum when combined with a probiotic yoghurt and administered to diarrhoea dominant IBS (IBS-D) patients resulted in less abdominal pain, cramping and less frequency compared with the control IBS-D receiving just the probiotic yoghurt.  Acacia gum has demonstrated the ability to bulk up the stool reducing diarrhoea in several studies.


Daily supplementation with 10-15gms/day of Acacia increased butyrate producing species of bacteria from the Bifidobacterium family such as B.longum and B.adolescentis.   B.longum supplementation for 30 days in humans resulted in lower anxiety scores and other longum strains reduced anxiety-like behaviour in colitis induced mice.   It enhanced the immune system response and reduced inflammatory markers associated with liver disease possibly from the SCFA’s it produces.


So what to take away from all of this information?


‘Diversity on the plate equals diversity in the gut’ – Glenn Taylor


According to Tim Spector, Professor of genetic epidemiology and author of “The Diet Myth” ‘you are never eating alone’ so always make sure you have something on your plate for your beneficial friends.

If you are new to these fibres be sure to start slowly and work up to your tolerance.  Also be aware that if you have some bad bugs some of these fibers can also feed them so important to clear up any dysbiosis and always take a good probiotic and eat your fermented foods along with these prebiotics.


You can chart how many different types of healthy unprocessed foods you can consume in a week to support your symbiotic community by making up a 50 – 100 food grid.  It’s not that hard, follow Alex and Edie Elliott’s example as these girls nailed 100 foods in 6 days quite a buffet for the gut bugs.

Super star 3 year old Lilly Maskell is another terrific example eating a whopping 50 different healthy foods in just 4 days!


Nicola Callan
Clinical Nutritionist (Bsc Health Science) Naturopathy (Adv. Dip.) Colonic and FMT Therapist

kasia burke photography