All About Probiotics

Probiotic is the “in” word now. It is not only associated with food and supplements, but is starting to appear in skincare, too. What are probiotics, and what is the big deal about them, you ask? This article will provide you with all that you need to know!

Table of Contents

What are probiotics?

Probiotics, as defined by the World Health Organisation, are ‘live microorganisms which when administered in adequate amounts confer a health benefit on the host’. These probiotics include bacteria and a particular yeast strain, but the majority of these probiotics are bacteria. That is why probiotics are sometimes referred to as “friendly bacteria”. Most of these live microorganisms are found in the colon (large intestine) which is the last part of the gastrointestinal system.

How do they work?

Probiotics restore good microorganisms in the body. This is especially important after a period of antibiotics, as antibiotics kill off all bacteria, both the good and the bad, in our gut. If these good microorganisms are not replaced, the patient’s gut will have an imbalanced ratio of good to potentially bad microorganisms. This could lead to opportunistic gastrointestinal infections.

What are probiotics and how do they work?

Why are probiotics important?

Basic roles of probiotics

1. Gut health

Mention the word, bacteria, and most people would associate it with bad things or germ. But guess what? Our body is full of good and bad bacteria, and probiotics are the good guys. In fact, probiotics are important for our gut health and overall well-being. They ensure that there is a good balance between the good and bad bacteria.

Probiotics line our digestive tract, thus are involved in maintaining healthy digestion, helping our body to absorb nutrients; make important vitamins, and fight against numerous infections that could damage our internal systems. The last point is because probiotics can help maintain the integrity of our intestinal lining, thereby preventing against leaky gut.

Leaky gut happens when the lining of our intestine gets damaged, allowing substances which it does not normally allow to pass through, to enter the bloodstream. Examples of these substances are proteins, toxins or undigested food particles. Our immune system recognises these substances as foreign, thereby mounting an immune response, which is known as “inflammator”. Probiotics can help dampen this inflammatory response by producing anti-inflammatory substances.

2. Managing digestive issues

Probiotics have also been shown to be helpful in the management of irritable bowel syndrome (IBS) by alleviating some of the symptoms of IBS. Common symptoms include gas, bloating, constipation and diarrhoea. Probiotics can also be useful in fighting against Helicobacter pylori (H. pylori) infections. H.pylori is said to be the main bacteria causing most gastric and peptic ulcers.

Other studies have shown that probiotics helps in the management of inflammatory bowel disease (IBD). This is only for maintaining remission of ulcerative colitis and pouchitis, as concluded by current evidence. One thing to note though, IBS and IBD are not the same. IBS is a functional disorder, meaning the gastrointestinal system looks normal, but it does not work as it should. Typical symptoms include gas, bloating, crampy pain, mucus in stools, constipation and diarrhoea. IBD, on the other hand, is more serious – there is usually inflammation, ulcers, and/or other damages to the bowel.

Scientists are unable to put a finger on what is/are the actual cause(s) of IBD.  However, it is proposed that IBD “may be due to inappropriate immunological response to intestinal bacteria. It may also be due to a disruption in the balance of the gastrointestinal microbiota in genetically-susceptible individuals”. Environmental factors including resident and transient microorganisms in the gastrointestinal tract and dietary components play a role in IBD. Examples of IBD include ulcerative Colitis, Crohn’s Disease and pouchitis.Your mood and gut bacteria.

3. Production of important nutrients

As mentioned earlier, the production of some important vitamins – B12, B1, B2 and K, and short-chain fatty acids (SCFAs) involve probiotics. The functions of  Vitamins B1, B2 and B12 include proper metabolism of carbohydrates, proteins and fats in our food, whilst Vitamin K helps in blood clotting. Vitamin B12 is also important for the manufacture of red blood cells and proper nerve function. When gut bacteria ferment dietary fibre (prebiotics) in our colon, it produces SCFAs. This leads to the absorption of the fatty acids into our bloodstream which then perform many metabolic functions. Besides, as the main source of energy for cells that line the colon (colonocytes), SCFAs support proper growth and differentiation of these colonocytes. The last two reasons are why SCFAs are vital to colonic health as SCFAs ensure the colonocytes are healthy.

Examples of SCFAs include acetate, propionate, and butyrate. Of the three SCFAs, butyrate is the most preferred fuel source of colonocytes.

Emerging role of probiotics

1. Emotional and mental health

There are some researchers suggesting a close relationship exists between our gut microbiome and our emotional and mental health. In the last decade, neuro-gastroenterology research has shown that there exists a lot of “communication” between the gut and the central nervous system. Alternative terms include the “gut-brain axis” or “microbiota-gut-brain axis”. This is a two-way communication network, and it takes place between the gut microbiome and brain function.

This communication pathway involves the central nervous system (CNS), the autonomic nervous system (ANS), neuroendocrine system, and immune system. The CNS includes the nerves in the brain and spinal cord, while the responsibility of regulating some body processes which we do not have much control over (i.e. is involuntary) falls to the ANS. Such body processes include blood pressure, breathing and heart rate, digestion, metabolism, urination and defecation. Always active, the ANS works by receiving signals from the CNS and passing onto other parts of the body, and vice versa. The nerves that make up the ANS include nerves of our internal organs like the blood vessels, heart, stomach, intestines, liver, and bladder.

The relationship between our gut microbiome and our emotional and mental health is known as the “gut-brain axis” or “microbiota-gut-brain axis”.

The role of probiotics in emotional and mental health

A study involving 40 healthy females found women with a higher percentage of the Prevotella species of bacteria in their stools more likely to experience negative emotions after having shown negative images compared to women with a higher percentage of the bacteroides species of bacteria in their stools.

In addition, a systematic review by Wallace and Milev have found that there is a possibility that probiotic supplementation could have a positive effect in improving symptoms of major depressive disorder (MDD), which include low mood, anxiety and cognitive symptoms, with no serious side effects reported. A systematic review “summarises the results of available carefully designed healthcare studies (controlled trials) and provides a high level of evidence on the effectiveness of healthcare interventions. Judgments may be made about the evidence and inform recommendations for healthcare”. Of all the MDD symptoms mentioned, anxiety appeared to have the most improvement with probiotic supplementation.

Whilst these findings seem promising, the authors of the study concluded by saying that there is a need to conduct more studies before using probiotics as a front-line treatment for reducing symptoms of MDD, including determining the exact mechanism(s) of the effects of probiotics. This is because characteristics of the participants involved in the studies reviewed were varied, and it is not clear how differences in age and gender could impact on probiotic effects. Furthermore, researchers have yet to identify what is the most effective dose, strain and duration of probiotic supplementation in improving mental health. Hence medical therapy is still the chosen line for treatment of MDD, at least for now.

2. Skin health

Another new discovery is the relationship between probiotics and skin, especially in terms of how probiotics (oral or topical application) can benefit the management of skin conditions such as eczema, acne and rosacea. Here are some of the possible ways in which probiotics can benefit our skin.

a. Topical application
  • When applied to the skin, probiotics form a protective layer on our skin. This (protective) layer protects our skin cells from invasion by bad bacteria and parasites, hence stopping an immune system response from happening.
  • Substances produced by probiotics sometimes possess antimicrobial effects – this means that probiotics can help kill off those bad bacteria lurking around on the skin.
  • The calming effect of some strains of probiotics, when applied on the skin, stops skin cells from producing substances that trigger the immune system to result in acne or rosacea flare-ups.
b. Oral consumption

Just like how probiotics benefit our emotional and mental wellbeing, oral consumption of probiotics, too, benefits our skin through positively impacting the “gut-brain-skin axis”. When consumed, probiotics strengthen our intestinal lining (in other words, probiotics can help prevent against leaky gut), thereby preventing harmful toxins from escaping our gastrointestinal tract and into our bloodstream to trigger an immune response. This immune response can then trigger an acne or rosacea episode.

With all that is being said, dermatologists from the American Academy of Dermatology advised that more research studies still need to be done to determine whether oral or topical probiotics, or a combination of both, is/are better for treating skin conditions, and the exact mechanisms. However,  you can use probiotics in combination with prescription medications or topical applications, and a healthy diet, to treat acne and rosacea. People suffering from such skin conditions should discuss with their dermatologists regarding the inclusion of probiotics into their daily diet.

The emerging role of probiotics.

What can upset this good balance of gut microflora?

  • Stress, especially if it is chronic.
    • Chronic stress is a risk factor for prolonged inflammation.
    • Because inflammation is an immune response, hence prolonged immune changes may alter the gut environment, which subsequently affects the gut microbiota population.
  • Poor quality diet.
    • i.e. diet that is high in processed foods (aka “junk foods”) AND low in dietary fibre
  • Imbalance of gut microbiota (dysbiosis).
    • The main culprit: prolonged intake of antibiotics

Where can I find probiotics?

  • Fermented foods such as yoghurt, kefir, miso, kimchi, tempeh and sauerkraut.
  • Probiotic supplements, either in capsules or powder form. The exact dose, strain(s), means of delivery, and/or the period of viability are still unclear, and will most probably vary with the strain(s) and the type of condition(s) that is to be treated.

Kefir Probiotics for health and skin


Types of probiotics


One of the most common probiotic strain, you can find the Lactobacillus family in yoghurts and other fermented foods. This probiotic species produces lactase, the enzyme that is in-charge of digesting the milk sugar, lactose, as well as lactic acid. Lactic acid helps fight against pathogenic bacteria in our body. Lactobacillus is commonly found in the mouth, small intestine and vagina.

Each strain of Lactobacillus probiotic performs a different function in the body. The species name (followed by the strain name) helps in the identifying of each strain – e.g. You can write Lactobacillus acidophilus as that or simplify it to “L.acidophilus”. Regardless of how the name is written on food or supplement labels, it should always be in italics.

Let us now go through the various roles each lactobacillus strain has in the body.

L. acidophilus

A probiotic strain highly resistant to breakdown by digestive enzymes and usually found in the small intestine and vagina. It plays a part in the digestion of lactose and other polysaccharides (long chains of carbohydrates), preventing growth of bad bacteria and reducing the concentrations of carcinogenic (cancer-causing) enzymes in our intestines. You can find L. acidophilus in yoghurt and fermented soy products (e.g. miso).

L. bulgaricus

A probiotic closely related to L. acidophilus and usually used in yoghurt and cheese production. L. bulgaricus mainly lives in our gastrointestinal tract, and as such, it helps keep our gut healthy.

L. rhamnosus

A probiotic strain with gut-protective functions. One particular strain and the most widely used probiotic strain, the L. rhamnosus GG (LGG) has many well-documented clinical benefits such as preventing and treating gut infections and diarrhoea caused by pathogens like Escherichia coli, rotavirus, Clostridium difficile, and Candida species in the young and the old. This is due to its exceptional ability to adhere to gastrointestinal epithelial cell surfaces.

LGG is said to inhibit the production of pro-inflammatory compounds (aka cytokines) and enhance the actions of our innate and acquired immunity.

LGG and allergies

Due to its potential immunomodulatory function, LGG inhibits the production of pro-inflammatory compounds (aka cytokines). It also enhances the actions of our innate and acquired immunity. As the body’s first line of defence against common microorganisms, it helps to maintain the level of infection in our body. Acquired immunity, on the other hand, mounts a specific response to a specific pathogen. This usually comes into play when the innate immunity is unable to fight the pathogen. The acquired immunity is responsible for recognising and killing specific infectious pathogen. This ensures that the pathogen does not cause disease later. Sometimes known as the “adaptive immunity system”, the acquired immunity system usually requires 4-7 days to take effect. Hence, the innate immunity is important within this period to control the level of infection in our body.

LGG and infants

One study found that giving infants LGG-fortified milk 2-4 weeks while in the mother’s womb and 1-year post-birth, resulted in a lower occurrence of atopic dermatitis (e.g. eczema). However, the authors concluded a low level of evidence. Another study conducted by Kalliomaki and colleagues also found an inverse relationship between prenatal maternal (2-4 weeks) and postnatal paediatric (6 months) LGG administration and incidence of eczema in infants/children born to families with atopic disease. These kids were followed up at the ages of 2, 4 and 7.

However, the same (good) results proved unrepeatable in another study conducted by Kopp and colleagues when they used this protocol. Kopp and colleagues suggested an attribution in the differences in results to the differences in the ethnicity – Finnish for Kalliomaki and colleagues’ study versus German for Kopp and colleagues’ study. This also includes the age of the participants involved in their research and probiotic formulations. Hence, more research needs to be conducted before considering LGG as the mainstream treatment for atopic eczema.

L. reuteri

Usually found in the mouth and intestine, this probiotic strain may have some benefit in treating acute onset infectious diarrhoea. Acute onset infectious diarrhoea is a type of diarrhoea which occurs suddenly due to a gut infection, e.g. food poisoning. Such diarrhoea usually lasts for a short period of time – a few days. Besides L. reuteri, LGG is another probiotic usually used in the treatment of acute diarrhoea. Between the two (probiotics), LGG is more effective in reducing both the duration and severity of the acute diarrhoea.

L. casei

Another probiotic with gut-protective and immunomodulatory effects. It counteracts the action of H. pylori (therefore this bacterium is unable to stick to our gastric epithelium and invade the stomach). This enhances the effects of innate immunity system and dampens inflammatory response by decreasing the secretion of proinflammatory cytokines. H. pylori is the bacteria responsible for infecting the stomach and may cause gastritis and ulcers in the host. In addition, L. casei can increase the number of secretory immunoglobulin A (SIgA)-producing cells in our intestines. SIgA plays an important role in protecting and regulating intestinal mucosal immunity. For example, it limits access of mucosal pathogens into the bloodstream.



L. plantarum

Like L. caseri, L. plantarum supports gastrointestinal health by preventing alterations in gut microflora populations. It prevents entry of “bugs” from our gut into the bloodstream by ensuring good intestinal barrier function, and inhibits the action of Clostridium difficile, often referred to as C. difficile. C. difficile is a bacterium responsible for causing a range of symptoms ranging from diarrhoea to a more serious condition like colitis (inflammation of the colon). People who are on prolonged periods of antibiotics and the elderly are at a high risk of getting C. difficile infection. This infection can also spread in nursing homes and hospitals. Because of its ability to normalise gut microflora populations, people with irritable bowel syndrome use L. plantarum to support healthy levels of gut bacteria.


Another common probiotic found in dairy products, and present in large numbers in the guts of both breastfed and formula-fed infants. However, there exist slight differences in the types of Bifidobacterium species recovered in the faeces of breast-fed and formula-fed infants – mainly attributed to differences in the diets of these infants. You can find the following Bifidobacterium species common in breast-fed infants.

B. bifidum

Main probiotic found in healthy colons wth low levels usually found in infants with allergies and as age increases. Modulates activity level of adaptive immunity and works alongside with L. acidophilus to support healthy gut microflora levels when on antibiotic treatment.

B. longum

One of the most dominant Bifidobacterium species found in our gastrointestinal tracts and probiotic formulas. Said to be able to decrease inflammation level in people with ulcerative colitis [26]. This probiotic species has two subspecies – Bifidobacterium longum subsp. longum (B. longum), and Bifidobacterium longum subspecies infantis (B. infantis).

B. infantis

Commonly found in intestinal tracts of infants, but seldom in that of older adults. Some research has suggested B. infantis to be beneficial in alleviating IBS symptoms, and reducing levels of inflammation in people with ulcerative colitis (a type of IBD) due to its ability to decrease production of pro-inflammatory compounds.

One other important function of B. infantis is its ability to metabolise human milk oligosaccharides (HMOs), which are long chains of carbohydrates that are high in and unique to breast milk. B. infantis is the only Bifidobacterium with the ability to metabolise HMOs.

What are HMOs?

HMOs play various important roles in a growing infant, one of which is for its prebiotic properties, i.e. HMOS stimulates and supports the growth of B. infantis in the infant’s gut, and this is important to establish a gut microflora with health benefits later in life for the breastfed neonate. It is for this reason why probiotics or milk containing B. infantis is given to premature babies.

B. infantis can also help to protect against necrotising enterocolitis. Necrotising enterocolitis is a serious (often fatal) disease affecting the intestines of premature babies. Bacteria attacks the (premature infant’s) intestinal walls, infecting and inflaming the intestines and eventually destroying and perforating the intestines. When that happens, stools will spill into the infant’s abdomen, resulting in infection and death. B. infantis is commonly found in probiotic supplements, used in the making of fermented foods (yoghurt, sauerkraut, and cheese), and added to infant formulas.

Saccharomyces boulardii

A type of non-pathogenic probiotic yeast. Due to its ability to improve the function of our gastrointestinal lining, it protects against or treats various types of diarrhoea (antibiotic-associated diarrhoea, Traveller’s diarrhoea), and other digestive issues such as H.pylori infection, C. difficile infection, IBS, and parasitic infections.

Saccharomyces boulardii improves the function of our gastrointestinal lining.

When’s the best time to take probiotics?

“Should I take probiotics on an empty stomach or with food?” is a commonly-asked question when it comes to probiotics use. Although there is no one right answer, one thing’s for sure – to get the best out of the probiotic supplement, these friendly bacteria would need to survive the acidic gastric environment and reach the lower intestinal tract intact. Proponents of taking probiotics with or immediately after meals mention food protects the probiotics from gastric juice through its buffering effect, hence allowing these probiotics to reach the large intestine intact and exert their beneficial effects. This comes as no surprise as probiotics have always been consumed in the form of fermented foods, e.g. yoghurt, cheese, kimchi, through the whole of evolutionary history.

There are two things to note though when it comes to consuming probiotic supplements:

You should not consume probiotic supplements with hot foods as the high temperatures (of these foods) can kill off these delicate friendly bacteria, and take probiotics separately from antibiotics. Leave at least a 2-hour time gap between probiotics and antibiotics consumption.

Probiotic vs prebiotic

Most people tolerate probiotics well, and probiotics are generally considered safe for these people. In the starting phase of introduction, there may be some slight gastrointestinal discomfort (bloating, gas). These (discomfort) symptoms should subside once the gastrointestinal system has adapted to the probiotics. However, in people with compromised immune systems (e.g. HIV, AIDS), probiotics could lead to dangerous infections. Hence, t5hese individuals should speak with their doctor prior to consuming probiotics.

Unlike probiotics, prebiotics carry little safety concerns. They may lead to gastrointestinal discomfort such as gas and bloating if introduced too quickly into the diet, or excessively consumed in one sitting. To avoid these uncomfortable symptoms, introduce one new prebiotic food into the diet every 1-2 days, or take care to not consume too much (of prebiotics).

Prebiotics vs Probiotics.

Prebiotics – food for probiotics

Do not confuse probiotics with prebiotics, which are dietary fibres that help feed the gut microflora. In other words, prebiotics are food for the probiotics. Prebiotic classification factors in certain conditions – resistance to digestion and absorption, fermented by gut bacteria in the gastrointestinal tract, and selectively stimulating the growth and activity of gut bacteria that eventually contributes to the host’s health and wellbeing. Upon reaching the colon, the fermentation of prebiotics by the probiotics produces carbon dioxide, hydrogen and methane gases, as well as SCFAs.

Good food sources of prebiotics include chicory root, dandelion, Jerusalem artichoke, asparagus, garlic, onions, leeks, banana, barley, oats, apples.

Including both probiotics and prebiotics into our diets ensures our digestive system is in tip-top condition.

References,-spinal-cord,-and-nerve-disorders/autonomic-nervous-system-disorders/overview-of-the-autonomic-nervous-system Accessed 22 January 2018