Prebiotics & Health
Prebiotic and probiotics may sound the same but their roles in the digestive system are entirely different. Prebiotics are promising but less understood compared to probiotics. In this article, probiotics will briefly be mentioned but prebiotics will be the primary focus.
These are live, friendly bacteria that line that intestinal tract. There are over thousands of bacterial species in the gut that promote good digestion, some good and some bad depending on our eating habits and lifestyle (1). Different foods can induce growth of both detrimental and beneficial bacteria in the gut microbiome. The two probiotic bacteria, Lactobacillus and bifidobacteria, are commonly found in probiotic supplements and food.
Sources: yoghurt, sauerkraut, kefir, kimchi, and supplements
Prebiotic acts like a fertiliser that enriches the beneficial bacteria that is present. Prebiotics are non-digestible oligosaccharides (special types of fermentable fibre) that benefit the body through increasing the levels of friendly bacteria in our intestine.
Synbiotics are typically sold as supplements are synergistic combinations of pro- and prebiotics.
Possible Health Benefits
By promoting the growth of friendly bacteria, these bacteria can perform important health functions including:
Prebiotics play an integral role in digestion and gut health. When harmful bacteria are present in high numbers, also known as dysbiosis, has been observed in certain diseases such as coeliac disease, inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), GI infections, antibiotic-associated diarrhoea (AAD) (2).
According to a report published in The Journal of Nutrition, prebiotics has shown promising benefits in people struggling with digestive disorders including (3):
inflammatory bowel disease (IBD)
irritable bowel syndrome (IBS)
NOTE: Please see a doctor or dietitian if you have any of these conditions before following any of the advice. A dietitian may provide first-line advice with IBS or recommend a short-term low FODMAP diet if necessary. Dietary advice would vary depending on the individual!
The overgrowth of unhealthy bacteria, dysbiosis, can cause inflammation in the body. Inflammation is closely linked to chronic diseases such as type 2 diabetes, obesity, heart disease and allergies.
Prebiotics are fermented into short-chain fatty acids (SCFA) like acetate, propionate, and butyrate. Of which, butyrate is considered the most beneficial in terms of colonic health (4).
A healthy microbial balance, then, promotes an anti-inflammatory effect in the intestinal tract and across the body’s systemic organ systems which can be protective against these diseases (5).
Strengthens the immune system
Nearly 70% of the immune system is located in the gut (6). The production of SCFAs by prebiotics may also play a role in improving immune function. In animal studies, SCFAs increases T helper cells, macrophages, and neutrophils, and natural killer cells which of all are involved in immune function (7). By strengthening your immune system, your body can defend you against disease-causing organisms.
Numerous experimental studies have reported a reduction in the incidence of tumours and cancers after feeding specific food products with a prebiotic effect (8). Butyrate produced by the microbiota has been shown to reduce the incidence of colon cancer by inhibiting cancer cell proliferation via histone deacetylases (HDACs) (9).
Supplementation of Inulin, a prebiotic, led to a reduction in LDL cholesterol (bad cholesterol), triglycerides, and blood sugar levels in multiple studies all of which are predictors of cardiovascular disease (10, 11, 12).
Improved calcium absorption and bone density
Daily consumption of 8 g/day of prebiotic short- and long-chain inulin-type fructans in combination with calcium in pubertal adolescents significantly increases calcium absorption and enhances bone mineralisation (14).
This could be quite important in postmenopausal women, adolescents, athletes.
Controls appetite and aids weight loss
Oligofructose has prebiotic effects and the supplementation of 21 grams per day for 12 weeks in healthy adults led to a reduction in body weight and improvement in glucose regulation. Alterations in hormone production such as ghrelin, the hunger hormone, and PYY, the satiety hormone may contribute to a reduction in energy intake (15).
Our gut acts as our “second brain” as it contains around 100 million nerves. Through this, the gut microbiota affects both our physical and psychological health (16). Studies have shown that when we are experiencing troubles in our gut such as irritable bowel syndrome (IBS), bloating, and diarrhoea, these are all related to depression and anxiety (17).
When prebiotics FOS and GOS were administered in mice, it led to a reduction in the stress hormone, corticosterone, and depression-like and anxiety-like behaviour (18). Hence, by improving gut health with prebiotics, you may experience a better sense of emotional well-being.
Since our beneficial bacteria work so hard to take care of us, we need to make sure we are returning the favour. Do yourself and your gut bacteria a favour by eating plenty of these prebiotic foods.
Types of Prebiotics
A fibre is considered to be prebiotic if it fits the following criteria (19):
Resists digestion and absorption in the upper gastrointestinal tract
Is fermented by the intestinal microflora
Selectively stimulates the growth or activity of good intestinal bacteria
There are various types of potentially prebiotic fibres that come in the form of oligosaccharides, resistant starches, and disaccharides.
Common examples of prebiotic fibres that cause remarkable changes in the gut microbiota found in food and supplements include:
The different types of prebiotics. * - the groups that will be discussed. (20).
More and more substances are being recognised as prebiotics (21).
Different fibres produce various amounts and ratios of short-chain fatty acids (SCFA), some of which fermented quicker than others which may lead to excessive gas production.
Shorter chain molecules like fructo-oligosaccharide (FOS) are fermented more rapidly than longer chain molecules like inulin (22).
Fructooligosaccharides (FOS) are fermented and metabolised to form short-chain carboxylic acids such as acetate and lactate. Due to their prebiotic effect, FOS are increasingly added to food products and infant formulas to improve microbiota health (23).
Inulin is one of the most well-known prebiotic that travels through our bodies from the small to large intestine. It is made up of chains of fructose, also termed as a fructan. Once this insoluble fibre reaches the colon, it is fermented by the healthy microflora into butyrate (24).
In each gram of inulin, there are only 1.5 calories making it relatively low in calories (25).
Inulin in 100 grams of the following foods (26):
Chicory root inulin-derived (FOS) Inulin is often written on product ingredients lists as chicory root fibre.
Note: It’s good to ease into eating Jerusalem artichokes, as they may cause distress to people with sensitive digestive tracts.
These are chains of galactose units that are indigestible by the intestine and fermented by the gut bacteria. Total amount and speed of SCFAs production increase with GOS administration (27). Experiments have shown that GOS is likely the most efficient type of prebiotic to stimulate the growth of bifidobacteria (28, 29).
Resistant starch reaches the colon largely intact and encourages the growth of friendly bacteria. Resistant starch carries many health benefits with one of the most promising aspects is its ability to improve insulin sensitivity and is less likely to cause a spike in glucose levels after meals (30, 31, 32).
In one study, overweight and obese men who consumed 15 or 30 grams of resistant starch per day has been shown to improve insulin sensitivity (33).
Remember to start with small doses and gradually increase the amount as tolerated. As your gut flora changes and adapts, it is typical to see increases in gas production and bloating.
These are found in grains, seeds, and legumes. Surprisingly it is also found in pasta or rise that has been cooked and cooled.
High (> 10 grams)
Red beans (cooked)
Brown rice (cooled)
Medium (1~10 grams)
Low (<1 gram)
Grams of resistant starch per 100 grams. A full list can be found at Free the Animal.
The centres for disease control and Prevention (CDC) points out that the use of commercial prebiotics is generally safe but there are rare cases where a person can become sick after ingesting too much prebiotics (36).
As everyone has significantly different varieties of bacteria living in our body, the amount recommended differs in everyone (37). Those with autoimmune conditions and digestive disorders may benefit from increased prebiotic consumption.
Prebiotics are indigestible and hence, too much can make you feel bloated. Remember to start by taking small doses and gradually increase your intake. Other common side effects include gas, constipation, loose stool and loss of appetite that occurs when you start this regimen.
In addition, many prebiotic foods are also considered high in FODMAPs and studies on whether increasing prebiotic intake can be of help in reducing irritable bowel syndrome (IBS) are mixed (38, 39). Without enough evidence, it is not recommended to take high doses in those with IBS. Instead, consider asking help from your GP or dietitian!