Probiotics Explained: 8 Questions Answered | Purolabs

Gut health has moved from niche nutrition science to mainstream health conversation in a remarkably short time, and for good reason. The evidence linking the gut microbiome to immune function, mental health, skin health, metabolic health, and even sleep quality has grown from promising to genuinely compelling over the past decade.

Probiotics sit at the centre of that conversation. But as with anything that becomes popular quickly, the market is now saturated with products of wildly varying quality, and the questions people have about them are becoming more sophisticated. Here are the eight questions that come up most often, answered with the clarity they deserve.

1. What are probiotics, and how do they work?

Probiotics are live microorganisms (primarily bacteria, but sometimes yeasts) that, when consumed in adequate amounts, confer a health benefit on the host. They work through several mechanisms: they colonise the gut (even temporarily), compete with harmful bacteria for resources, produce short-chain fatty acids that nourish the gut lining, modulate immune responses, and communicate with the nervous system via the gut-brain axis.

The key phrase in the definition is 'in adequate amounts'. A probiotic supplement that does not deliver sufficient live bacteria to the intestines, either because the CFU count is too low, the bacteria are not acid-resistant, or the capsule releases its contents in the stomach rather than the gut, which is not going to produce the benefits the research describes.

2. What does CFU count mean and how much do you need?

CFU stands for Colony Forming Units, essentially, the number of viable bacteria in each dose. Higher CFU counts do not automatically mean better results, but they matter in the context of a well-designed formula. To have a meaningful impact on the gut microbiome, research generally supports a minimum of 10 billion CFU per dose for general gut health maintenance, with higher counts appropriate for specific therapeutic applications.

What matters alongside CFU count is delivery. Bacteria need to reach the intestine alive to be effective, which means surviving the acidic environment of the stomach. Delayed-release capsules, which are designed to pass through the stomach intact and dissolve in the intestine, are significantly more effective at delivering live cultures to where they need to be.

3. Does the number of strains matter?

Yes, and this is one of the most important quality indicators to look for. A diverse gut microbiome is a healthy gut microbiome. Multi-strain probiotic formulas, those containing multiple species and subspecies of beneficial bacteria, which have consistently outperformed single-strain products in research, because different strains have different effects and colonise different areas of the gut.

Research from the University of Oxford found that diverse gut bacterial communities offer significantly stronger protection against harmful pathogens than less diverse ones, through a mechanism called nutrient blocking. When multiple beneficial strains are present and competing for resources, there is less ecological space for harmful bacteria to establish themselves.

The most clinically studied strains to look for in a probiotic are Lactobacillus acidophilus, Lactobacillus rhamnosus, Bifidobacterium bifidum, and Bifidobacterium longum. Lactobacillus rhamnosus is notable for its antibiotic-resistant properties and its well-researched role in IBS symptom management.

4. Are probiotics only for digestive problems?

This is a misconception worth addressing directly. Because 70% of the immune system resides in the gut-associated lymphoid tissue, and because the gut produces around 90% of the body's serotonin, the effects of a healthy microbiome extend far beyond digestion. Research has linked probiotic supplementation with improvements in:

•    Immune function, multiple studies show probiotics reduce the frequency and duration of upper respiratory tract infections

•    Mental health, a growing body of psychobiotic research suggests specific strains may help reduce anxiety and depressive symptoms by modulating the gut-brain axis

•    Skin health, the gut microbiome influences the skin microbiome, and probiotics have shown benefit for inflammatory skin conditions including acne, eczema, and rosacea

•    Vaginal health, probiotics help maintain a healthy vaginal microbiome, reducing the risk of recurrent thrush and bacterial vaginosis

•    Sleep quality, the gut microbiome is involved in the production of melatonin precursors and the regulation of circadian rhythms

"Cured my IBS symptoms. I can now eat anything since taking your biotic complex daily."

– Howard W., verified Purolabs customer

"I call biotic complex my miracle tablets. Suffered for years with irritable bowel. Within a few days of taking them the change was amazing."

– Lynda C., verified Purolabs customer

Gut Health | IBS | Digestion | Immunity

Biotic Complex

4.4

Rated 4.4 out of 5 stars

550 Reviews

A daily boost of friendly bacteria to support a healthy gut microbiome - the key to digestive health, immunity and daily wellbeing.

Learn More

5. What is the difference between probiotics and prebiotics?

These are often confused and frequently used interchangeably, but they are distinct things that work best together.

Probiotics are the live beneficial bacteria themselves. They arrive in your gut, colonise (at least temporarily), and produce beneficial effects directly.

Prebiotics are non-digestible fibres that act as food for the beneficial bacteria already living in your gut. They are not bacteria themselves. They are what the bacteria eat. Common prebiotic sources include garlic, onions, leeks, asparagus, chicory root, and kiwi fruit.

A probiotic supplement that includes a prebiotic (sometimes called a 'symbiotic') is more effective than one that does not, because the prebiotic sustains and amplifies the effect of the probiotic bacteria once they reach the gut. Purolabs Biotic Complex includes 200mg of sugar beet prebiotic fibre for precisely this reason.

Dietary prebiotic sources are equally important. Aim for a variety of prebiotic-rich foods daily alongside supplementation for the strongest effect.

6. Should you take probiotics with antibiotics?

This is one of the most common and important questions around probiotic use. Antibiotics are broad-spectrum. They kill harmful bacteria but also indiscriminately damage the beneficial bacteria in the gut, which can lead to digestive disruption, increased susceptibility to infections, and sometimes antibiotic-associated diarrhoea.

Research supports taking a probiotic during and after a course of antibiotics, with an important caveat on timing. Take the probiotic at least two hours after each antibiotic dose, not at the same time, to reduce the risk of the antibiotic killing the probiotic bacteria before they reach the gut. Continue for at least two to four weeks after the antibiotic course ends, as full microbiome recovery can take several months.

Lactobacillus rhamnosus and Saccharomyces boulardii are the most studied strains for antibiotic-associated recovery.

7. Who should take probiotics every day?

Probiotics are safe and beneficial for most adults as a daily supplement. Those who particularly benefit include:

•    People with IBS, bloating, constipation, or diarrhoea

•    Those who have recently taken antibiotics or have a history of frequent antibiotic use

•    People with inflammatory skin conditions, including acne, eczema, or rosacea

•    Those experiencing frequent colds or infections, suggesting immune vulnerability

•    Women with recurrent thrush or bacterial vaginosis

•    Anyone experiencing anxiety, low mood, or stress-related digestive symptoms

•    Older adults, as microbiome diversity naturally declines with age

•    Pregnant and breastfeeding women, probiotics support both maternal gut health and infant immune development

8. What about probiotic foods versus supplements?

Fermented foods, live yoghurt, kefir, sauerkraut, kimchi, miso, and tempeh, which are genuinely beneficial and should be included in your diet regularly. They provide a variety of live bacteria along with the fibre, protein, vitamins, and other compounds that whole foods uniquely deliver.

However, probiotic supplements and fermented foods serve different purposes and are best thought of as complementary rather than interchangeable. Supplements provide consistent, measurable doses of specific, clinically studied strains in a form designed to survive stomach acid. The CFU count in most fermented foods is unpredictable, the strains are not standardised, and the bacteria are not protected from stomach acid in the way a well-designed capsule is.

The most effective approach is to eat a diverse, fermented-food-rich diet and take a daily multi-strain probiotic supplement. Neither substitutes adequately for the other.

Frequently Asked Questions

How long does it take for a probiotic to work?

Digestive symptoms such as bloating and discomfort often begin to improve within one to two weeks. Effects on immune function, skin, and mood typically take four to eight weeks of consistent daily supplementation to become noticeable. Long-term microbiome changes accumulate over months rather than days.

Can you take too many probiotics?

For most healthy adults, probiotics are very safe even at high CFU counts. Mild digestive symptoms, bloating, wind, or a temporary change in bowel habits, which can occur in the first week as the microbiome adjusts. These typically resolve without any intervention. Very high doses are rarely necessary for general health maintenance.

Do probiotics need to be refrigerated?

Modern freeze-drying techniques and delayed-release encapsulation mean that many high-quality probiotics, including Purolabs Biotic Complex, are stable at room temperature. Refrigeration is typically required for liquid probiotics and some older formulations. Always check the storage instructions on the product.

Are probiotics suitable during pregnancy?

Research suggests probiotics are safe during pregnancy and may be beneficial. Lactobacillus rhamnosus is the most studied strain for pregnancy, with evidence supporting benefits for maternal gut health and infant immune development. Always inform your midwife or GP of any supplements you are taking during pregnancy.

What is the best probiotic for IBS?

The strains with the strongest evidence for IBS specifically are Lactobacillus rhamnosus, Lactobacillus acidophilus, and Bifidobacterium bifidum. A multi-strain probiotic at 10 billion CFU or more, in a delayed-release capsule, is generally the most effective format. Purolabs Biotic Complex contains all three of these strains alongside 12 others, at 21 billion CFU per capsule.