Everything You Need To Know About Probiotics

How probiotic foods and supplements nourish your microbiome and improve your overall health.

Everything You Need To Know About Probiotics photo

What you need to know about probiotics

Probiotics are supplements and foods that contain beneficial bacteria and other microbes to help replenish those found naturally in our body’s microbial environment: the microbiome.

The bugs that make up the microbiome are largely found in the gut - but they also live in the mouth, ears, nose, throat, airways, urinary tract and vagina), as well as on the surface of the skin. This is because they have a largely protective role, working on the frontline of the immune system.

Microbiome, inflammation and health

Unfortunately, modern diets and various medications, including antibiotics, can knock the ecosystem of our microbes out of balance. This can leave us with a microbiome that contributes to disease rather than health.

A depleted and imbalanced microbiome (dysbiosis) – both in the gut and elsewhere in the body – has been linked to many inflammatory conditions, from eczema to arthritis. A key role of the microbiome is to help regulate such inflammation. There is also ongoing research into its relationship with other conditions that feature inflammation, such as dementia and neurological diseases, diabetes, cancer, cardiovascular disease and bipolar disorder.1-7

Probiotics and the immune system

The bacteria and other microbes that make up our microbiome form part of a physical barrier that helps protect us from infection. They also communicate with the rest of the immune system and can influence the production of white blood cells.

In a study using laboratory mice reared with germ-free guts, one group were given probiotics to repopulate them with bacteria and a second group remained microbe-free. Both groups were then infected with listeria, but only those on probiotics were able to produce the white blood cells they needed to fight the infection and survive.8 This suggests an essential role for the microbiome in protection from infection.

Probiotics and digestive health

Dysbiosis (microbial imbalance) in the gut can be caused by poor diet, infection, stress, medication and other factors.9 It has been linked to irritable bowel syndrome (IBS), inflammatory bowel disease (IBD: Crohn’s disease and ulcerative colitis), stomach ulcers, colorectal cancer and other digestive conditions.

Probiotic supplements have now been tested in a number of studies looking at digestive health. The beneficial bacteria L.reuteri and L. plantarum, for example, have both shown potential in helping to manage and prevent IBD. The probiotic yeast S. boulardii can be effective for the prevention and treatment of diarrhoea and also for treating IBS, Crohn’s disease, giardiasis and preventing the recurrence of C. difficile disease.11-13

Probiotics and the skin

The gut-skin connection is now well established and probiotic supplements are often recommended for skin complaints such as atopic dermatitis, psoriasis and acne.14,15

The probiotic supplement B. longum, for example, has been shown to help improve atopic dermatitis. Trials have begun using topical probiotics on affected skin too - one promising study used a lotion containing L. paracasei on mild to moderate acne. It makes sense, however, to address gut health too.16,17

Probiotics, stress and mood

In a double-blind, randomised study (so no one knew what they were given), healthy volunteers took either a probiotic supplement (containing Lactobacillus helveticus and Bifidobacterium longum) or a placebo for a month. Those who had been taking the probiotics had reduced levels of the stress hormone cortisol, which suggests their stress responses had been calmed. The probiotic group also had reduced scores for anxiety, depression and other mental health factors.18

It's also now recognized that a great number of gut microbes, including Lactobacillus and Bifidobaceria strains, produce neurotransmitters that affect mood and behavior, such as serotonin (the “happy chemical”), dopamine (associated with pleasure and reward) and GABA (a calming neurotransmitter).19

Testing for dysbiosis

So how can you test your microbes to see how much biodiversity or imbalance you have? You can choose a classic stool test that cultures (grows) the microbes in your sample and looks for specific pathogenic (disease-causing) microbes. Or there are more sensitive tests that use PCR (Polymerase Chain Reaction) technology to look for DNA evidence of both beneficial and pathogenic microbes. Both have value and pitfalls, so ask an experienced nutritional therapist to refer you for a good quality test and help you interpret the results alongside your current symptoms and case history. They can then help you put a plan together that’s tailored to you and what your body needs right now.

Probiotic foods

Depending on your individual circumstances, you might need to include more probiotic foods in your diet. Probiotic foods are fermented foods that still contain a good level of microbes – examples include kefir, kombucha, raw sauerkraut and apple cider vinegar “with mother” (i.e., unfiltered so it still contains the original ferment). For most people, small, regular helpings of these contribute to a healthy gut, with potential benefits of better digestion and overall health.

Prebiotic foods

These are fiber-rich plant foods that help to feed all the different kinds of microbes in the microbiome. The more different types of plant foods in your diet, the more biodiversity there will be in your microbiome, so it can be beneficial to mix up your vegetable, bean, lentil, grain, nut, seed and fruit intake throughout the week, month and year.

Probiotic supplements

There are a great many probiotic supplements out there these days, so it’s easy to get confused. Some people do very well on high-dose probiotic supplements, or perhaps those with a dozen or more strains, while others would benefit from starting with lower doses or a simpler formula and gradually building up. For most people, it is best to start with a low dose (up to 10 billion CFU) supplement containing at least 8 different strains of Lactobacillus and Bifidobacteria.

If you’re having trouble identifying what would work best for you, look for support from an experienced nutritional therapist.

When to take probiotic foods and supplements

Many people would benefit from a daily intake of probiotic foods and/or supplements. This doesn’t need to be a huge quantity, just a regular, small supply of beneficial microbes to support good microbial balance in the gut.

As antibiotics can lead to imbalance in the gut microbiome, it might be helpful to take probiotics alongside them – just at a different time of day. Probiotic use has been shown to reduce side effects such as diarrhoea in people taking antibiotics.20

Probiotics and histamine

Individuals with a histamine intolerance generally need to avoid probiotic (fermented) foods and certain kinds of bacteria that promote histamine release, such as certain strains of Lactobacillus casei and Lactobacillus bulgaricus.21 This is because histamine is processed in the digestive tract – certain microbes will help or hinder this process and might release additional histamine themselves.

If you find that probiotic foods or supplements give you discomfort or other unpleasant effects, consult a nutritional therapist for tailored support.


Probiotic foods and supplements provide beneficial bacteria and other microbes to help replenish and rebalance our microbiome.

The composition of our microbiome and the use of probiotics to support it are proving to be key factors in the strength of our immunity as well as in other important areas such as digestive health, skin health and mental health.

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