Probiotics

This is the single most common point of confusion when buying probiotics, and the short answer is: strains matter more than the headline CFU number.

A product with 15 billion CFU of a well-matched, specific strain will typically outperform a 100 billion CFU formula containing generic, poorly-researched strains. The reason is that probiotic benefits are largely strain-specific — research conducted on one strain of Lactobacillus doesn't necessarily apply to a different strain of the same species, even if the label only says "Lactobacillus."

That said, CFU isn't irrelevant. Research suggests beneficial effects can typically be seen across a range of 1 billion to 100 billion CFU per day, depending on the strain and your individual circumstances, so an extremely low CFU count for a given strain may simply be under-dosed.

The most useful approach: first identify whether the product lists specific, named strains (not just genus or species), then check whether the CFU count sits within a sensible range for that type of strain. A product that's transparent about both is generally a better sign of quality than one that leads only with a very large CFU number and limited strain detail.

Probiotics are live microorganisms — beneficial bacteria such as Lactobacillus and Bifidobacterium strains — that are taken as a supplement to support the existing balance of bacteria in the gut. Prebiotics, by contrast, aren't live organisms at all. They're typically fibres, such as inulin, that act as a food source for the beneficial bacteria already living in your gut.

You don't strictly need both, and many people start with one or the other depending on their goals. Some probiotic products include a prebiotic ingredient as part of the formulation — often described as a "synbiotic" approach — which is designed to support the probiotic strains once they reach the gut. Others are probiotic-only, with no added prebiotic fibre.

If you're new to this category, a probiotic supplement on its own is a reasonable starting point. If you're already taking a probiotic and want to support it further, or if you're focused primarily on fibre intake and gut bacteria diversity through diet, a separate prebiotic fibre supplement can be a useful addition. Diet remains the foundation either way — a varied diet rich in plant foods and fibre is the most consistent way to support a diverse gut microbiome over time.

Most probiotic supplements are formulated to be taken with food, typically with a meal, though this can vary by product and by the specific delivery technology used.

The reasoning behind taking probiotics with food relates to stomach acid. Standard capsules can lose a significant proportion of their live organisms to stomach acid before reaching the intestines — and food intake affects stomach acid levels and gastric emptying time, which can influence how many organisms survive the journey. However, products with delayed-release capsules, enteric coatings or microencapsulation are specifically designed to protect the organisms regardless of timing, so always check the product's own instructions rather than assuming a general rule applies.

Consistency matters more than precise timing for most people. Taking your probiotic at roughly the same time each day — whichever time you're most likely to remember — is generally more useful than optimising for a specific window. If you're taking probiotics following a course of antibiotics, it's often recommended to space them a few hours apart from the antibiotic dose, though your pharmacist can confirm specific guidance for your medication.

Probiotic supplements containing common strains of Lactobacillus and Bifidobacterium are generally well tolerated by most healthy adults as part of a balanced diet and lifestyle. However, there are a few situations worth being aware of.

Some people experience mild, temporary digestive changes — such as bloating or changes in bowel habits — when first introducing a probiotic, particularly at higher CFU counts. Starting with a lower CFU count and gradually increasing can help minimise these initial adaptation effects.

If you have a diagnosed digestive condition such as IBS, or any ongoing gastrointestinal issue, it's worth discussing probiotic use with your GP or pharmacist, as the most suitable strain can vary depending on the specific type of symptoms you experience. The same applies if you have a weakened immune system, are pregnant or breastfeeding, or are taking other medications regularly — a quick check with a healthcare professional is a sensible precaution before starting any new supplement.

For most people without underlying health conditions, probiotics containing well-established strains at reasonable CFU counts are considered a normal part of an everyday wellness routine.

This varies depending on the product, the strain, and what you're hoping to support — and it's worth setting realistic expectations from the outset.

Probiotics are generally intended for consistent, ongoing use rather than as a short-term fix. Because the gut microbiome is dynamic and influenced by diet, lifestyle and many other factors, a single course is unlikely to produce a lasting change on its own — which is why most probiotic products are designed to be taken daily, on an ongoing basis, as part of a routine.

Some people notice changes in digestive comfort within a few weeks of consistent use, particularly if they're introducing probiotics for the first time or following a course of antibiotics. For others, particularly those using probiotics as part of general daily wellness rather than to address a specific issue, the effects are more about ongoing support than a noticeable before-and-after change.

Diet and lifestyle remain the foundation. A probiotic supplement works best alongside, not instead of, a varied diet that includes fibre-rich plant foods, which themselves support a diverse gut microbiome. If you have ongoing digestive symptoms that don't improve, it's worth speaking to your GP rather than relying on supplementation alone.