Probiotics are a culture of ‘good’ bacteria. Probiotics can found in

  • A supplement (a pill or powder) of beneficial bacteria
  • In some foods – anything fermented and not pasteurized, as pasteurization will kill the bacteria. This includes sauerkraut, kimchi, lacto-fermented fruits and vegetables, non-pasteurized yoghurt, kefir, cheese and non-pasteurized meats like salami and some sausages.

Where do I start with probiotic supplements?

Any probiotic supplement has a either a single or different mix of different strains of healthy probiotic bacteria.

Regardless of claims, no one brand has the entire mix exactly as it occurs intestinally. It is not possible to manufacture certain strains of probiotics found in the gut. If dealing with a specific gut health issue then look for a strain of bacteria that is scientifically and clinically proven to contribute to improving that condition. If you are looking to treat a specific health issue with a probiotic, look at the available research and talk to your clinician about whether probiotic supplementation is necessary.

What should I look out for?

  • A probiotic supplement containing the right genus e.g. Lactobacillus, the right species e.g. Rhamnosus and the specific strain of the species e.g. LGG. Each genus and species can address different health concerns.
  • Be aware that whilst you may read research on the benefits of say Lactobacillus rhamnosus LGG, this does not mean the same benefits apply to all Lactobacillus probiotic supplements, and it does not even apply to other types of Lactobacillus rhamnosus. For example, L. rhamnosus Rosell-11 has been shown in some clinical trials to maintain gut health when taking antibiotics, and to reduce the risk of antibiotic-associated diarrhoea. However, L. rhamnosus GR-1 has not been shown to directly aid digestive health but has been shown to colonise in the vaginal tract and to help maintain vaginal microflora balance.
  • Look for CFUs or “colony forming units” on the side of the bottle. That’s how many bacteria you will receive per dose. Some of these bacteria are bound to die during transit to your intestines. Be aware that some probiotics may also be effective at dosages of 1–2 billion CFU per day, while others may require at least 20 billion CFU to achieve the desired effects.
  • What’s the shelf life of the CFUs? You don’t want just the CFUs at ‘time of manufacture.’ You also need to know how long the CFUs will retain their viability.

Look for valuable strains, including species of Lactobacillus and Bifidobacteria such as Lactobacillus acidophilus and Lactobacillus plantarum that reside in the small intestine or the upper gastro intestinal tract among your immune cells. Bifidobacterium lactis, Bifidobacterium longum, and Bifidobacterium bifidum reside in the large intestine or the lower bowel, which are also critical areas for health

Read more about the specific strains of probiotics and the claims around their health properties in this evidence review paper published in the International Journal of Environmental Research & Public Health.

Above all, if taking a probiotic in tablet form, check to see that the probiotic does reach the gut. Remember that any research published by manufacturers will be biased to benefit their product and sales.

When should I take probiotics?

There is no science to support taking probiotics either at night or in the morning. Taking them with or without food is the more important decision. The digestive tract can be hostile to probiotics due to the acidity of the gut rather than the time of day you take them.

It’s more important to take probiotics with food, not on an empty stomach. The reason is the pH balance. Stomach acidity is described in terms of pH – the lower the pH, the higher the acidity, whereas higher pH is more neutral.

On an empty stomach, the low pH (more acidic) is too harsh for bacterial survival. After a meal, the pH of the stomach contents rises to a more basic value of around 7, which is less acidic. That means there is less chance of the probiotics dying.  Always take with a full glass of water to help dilute stomach acid.

In a study found in Beneficial Microbes published in 2011, researchers found that probiotics taken within 30 minutes of a meal, or with the meal, survived in much higher numbers than if taken 30 minutes before a meal.

After working their way out of the stomach, the bacteria also have to survive the fluctuating pH of the small intestine. After leaving the stomach, bacteria with food are subjected to a lower pH, similar to the contents of the stomach.

Slightly lower down in the upper small intestine, the contents (food and probiotics) are subjected to bile and pancreatic juices that increase the pH making the environment more alkaline and more favorable for survival.

Should I take them at the same time as my antibiotics?

Probiotics need to be taken at least two hours before or after antibiotics. If you are taking any other prescribed medications discuss with your specialist or GP as to whether probiotics will cause any interactions if taken at the same time.

What are the issues around probiotics?

Probiotics are considered safe overall for healthy people; short-term side effects may include mild gas and bloating. But risks may be greater in those with complicated gastro-intestinal conditions.

A systematic review of probiotic information leaflets in the Annals of Internal Medicine in 2018 found that the reporting of adverse effects is often missing or inadequate. Thus always contact the manufacturer before starting a probiotic regime to discuss any existing health concerns you may have.

The outcome of studies provided by manufacturers depend on those participants with specific criteria who were recruited to take part in these studies. Remember, there is no current standard definition of ‘normal’ microbiota. One study published in the British Medical Journal noted: “The ability to assess the degree of dysbiosis improvement is dependent on the enrolled population and the timing of microbiological assays. The functional claim for correcting dysbiosis is poorly supported for most probiotic strains and requires further research”.

General commercial probiotic strains should be used cautiously by pregnant women, infants and young children and never given to premature infants. Always research or discuss with a health practitioner the appropriate strain of probiotic to take if pregnant or providing probiotic supplements to children.

If you are immunocompromised or have certain bowel problems such as Irritable Bowel Syndrome, Small Intestinal Bacterial Overgrowth or Crohns, avoid probiotics unless your clinician has advised usage. Even in healthy people, the reactions to probiotics vary widely, according to a study in Cell published in 2018.

Remember: probiotics are a live organism so they have a unique set of potential risks that other supplements don’t have. Your gut microbiota is unique to you, each person has their own unique mix and a commercial product that works for one may not work for you. Always discuss with a health practitioner if considering using probiotics.

Evidence for probiotics – are they worth it?

  • The best evidence for probiotics is for reducing diarrhoea, especially following antibiotic use. A 2010 review from the Cochrane Collaboration concluded that probiotics shorten episodes of acute infectious diarrhoea. A 2013 Cochrane review of 23 trials also concluded that probiotics may be effective for preventing antibiotic-related diarrhoea.
  • However, a 2012 research review in the Journal of the American Medical Association (JAMA) found that although probiotics reduced the risk of antibiotic-associated diarrhoea by 42% many of the studies had flaws and the findings should be interpreted with caution.
  • Two large, well-designed studies, in the Lancet in 2013 and the Annals of Internal Medicine in 2014, found that probiotics were no better than a placebo in preventing diarrhoea in older people taking antibiotics.
  • Other claims and evidence around promoting probiotics—that they lower cholesterol, alleviate allergic skin conditions (like eczema), treat ulcers, reduce the risk of colon cancer, ease anxiety and depression are of poor quality. Good longitudinal studies to support these claims is lacking and suggestions can be anecdotal.
  • Probiotics are not all alike. For example, if a specific strain of Lactobacillus helps prevent an illness or improves health and wellbeing, that doesn’t necessarily mean that another strain would have the same effect or that any of the Bifidobacterium probiotics would do the same thing. A promising study on a single strain of a particular species of bacteria should not be taken as proof that all probiotics work equally well. Everybody has a different gut microbiota. There will probably never be a one-size-fits-all probiotic.
  • Manufacturers of probiotics often select specific bacterial strains for their products because they know how to grow them in large numbers, not because they are adapted to the human gut or known to improve health.
  • The particular strains of Bifidobacterium or Lactobacillus that are typically found in many yoghurts and tablets may not be the same kind that can survive the highly acidic environment of the human stomach and from there colonize the gut. Many yoghurts and yoghurt drinks also contain high levels of sugar.
  • There’s also a cost factor – probiotic supplementation can be expensive.


Prebiotics are used in the gut to increase populations of healthy bacteria, aid digestion and enhance the production of valuable vitamins. Prebiotics can be found in carbohydrates and fruit and vegetables. They are resistant to heat, oxygen, stomach acids and enzymes. When ingested, they reach the lower gut intact and can help to nourish the good bacteria once there.

While all prebiotics are fibres, not all fibres are prebiotics. Not all forms of dietary fibre present in the majority of plant based foods and grains are selectively fermented by the bacteria in the gut. But they can still be of benefit to health as they help maintain regular bowel movements.

Prebiotics are also available in the form of food supplements such as ‘fructo-oligosacharides’ (FOS), Inulin, Polyphenols and Resistant Starches. Research indicates that FOS and Inulin are one of the most beneficial types of prebiotics for feeding our gut bacteria. Both Inulin and FOS are effective prebiotics that stimulate the growth of intestinal Bifidobacteria, without leading to a rise in serum glucose or stimulating insulin secretion. Polyphenols are naturally-occurring compounds found in in plants including fruits, vegetables, coffee, tea, and wine and have prebiotic properties.

A warning on prebiotics

It is recommended to work with a qualified health practitioner before modifying your diet especially if you have gastro-intestinal health conditions. Adding prebiotic foods into your diet could cause an increase in your digestive symptoms and a qualified health practitioner can address these issues.


Kefir is a great natural source of probiotic. The kefir grain contains about 30 strains of bacteria and yeasts, making it a very rich and diverse probiotic source.

Most commonly kefir is a fermented milk product (cow, goat or sheep milk) that tastes like a drinkable yogurt. It is made by adding kefir ‘grains’ to milk, milk substitutes or water for those who are lactose intolerant or avoiding dairy.

These are not grains in the conventional sense, but cultures of yeast and lactic acid bacteria that resemble cauliflower in appearance. There are two types of grains – dairy based and water based. Water based grains do contain sugar so if you are avoiding sugar early in treatment treatment or are on a medically controlled diet you may want to look at the milk based grains if appropriate.

Over a period of 24 hours or so, the microorganisms in the kefir grains multiply and ferment the sugars in the milk, turning it into kefir. Then the grains are removed from the liquid, and can be used again. So basically, kefir is the drink, but kefir grains are the ‘starter kit’ that you use to produce the drink.

Kefir can now be found ready made in most supermarkets or local grocery stores. The grains can be purchased online or at health food stores.

What are the issues around kefir?

  • Flavoured kefir contains added sugar in the form of cane sugar or cane syrup
  • Kefir contains varying amounts of saturated fat, depending on whether it’s made from whole or low-fat milk
  • While the probiotics in kefir can be beneficial, it isn’t for everyone. Side effects, though not very common, include gas, upset stomach and diarrhoea
  • Individuals with bowel problems should always speak with a qualified health practitioner about kefir before adding it to their diet.
  • Kefir naturally contains tyramine and histamine, which are both produced during the process of bacterial fermentation. Individuals with mast cell issues who have to strictly adhere to a histamine and tyramine restricted diet may need guidance around the consumption of kefir.
  • For those taking monoamine oxidase inhibitors to treat depression, please consider whether to drink kefir as this fermented drink’s high tyramine content may cause blood pressure spikes. Discuss with your GP or consultant.
  • Both tyramine and histamine are associated with migraines as well. For those who suffer from acute or chronic migraine consideration should be given to this before drinking kefir.


We rely on our gut bacteria to produce much of our essential nutrients and vitamins while they rely on us eating plants and fruits to provide them with energy and to produce healthy chemicals which keep our immune system working normally. Our gut bacteria help to produce micronutrients (like vitamins and antioxidants) from the food we eat, as well as break down macronutrients (carbohydrates, proteins and fats) to ease digestion. These bacteria also maintain the colon wall, helping with its barrier function and uptake of nutrients in our gastrointestinal tracts.

It is now understood that diet plays a significant role in shaping the microbiome, with experiments showing that dietary alterations can induce large, temporary microbial shifts within 24 hours. A research study published in 2014 in the Multidisciplinary of Microbial Ecology involving laboratory mice demonstrated that when fed an intensive high fat diet their microbes changed dramatically and for the worse.

The media is now increasingly highlighting the effect of sugar on the body and the increase in diabetes and obesity related illnesses in the adult population particularly in the UK and US.

Eating sugar gives increases the feel-good chemical called dopamine, which helps to explain why you’re more likely to crave a chocolate bar at 3pm than an apple or a carrot. Because whole foods like fruits and vegetables don’t cause the brain to release as much dopamine, your brain starts to need more and more sugar to get that same feeling of pleasure.

Chronic UTI sufferers regularly report flares over the Christmas and Easter holiday periods. When we eat a high-sugar diet, the undesirable bacteria thrive and start to grow out of control, while our beneficial bacteria dwindle in number.

Where do I start with diet?

Given your gut is a key immune system regulator and “second brain”, the modern Western diet lacks a great deal of variety and can easily disrupt the gut microbiome. It is high in processed and fried foods, sugar, carbohydrates and trans and hydrogenated fats. With busy, time poor lives, it is too easy to reach for the bar of chocolate, bag of crisps or sugary bun to get that quick fix. Supermarket prepared ready meals or takeaways are often the quickest option at the end of the working day.  It also helps that fast food and sugary treats are inexpensive in comparison to healthier options.

A healthy diet encourages eating plenty of fruit, vegetables, healthy fats, lean protein, and other plant-based foods. The “Mediterranean Diet” in a study in 2018 published in Frontiers in Nutrition noted “while the monkeys fed the Western diet experienced a 0.5 percent increase in the abundance of “good” bacteria in their gut, the beneficial gut bacteria of monkeys fed the Mediterranean diet increased by up to 7 percent”. It is also one of the most extensively studied diets to date, with reliable research supporting its use for improving a person’s quality of life and lowering disease risk.

Any change in diet must be tailored to your individual circumstances. A good starting point is to firstly look at your lifestyle and your budget and what dietary changes are possible based on these factors.  Then consider any dietary changes against how they will affect your bladder.

Find out more about diet and drink and your bladder.

Those with Irritable Bowel Syndrome (IBS), or who are Coeliac will already be aware of their own dietary requirements and should be under managed care through their consultant.

Think carefully about using Dr Google as an alternative, cheap option despite all the “advice” on there especially if you have other health issues.  Look for diets that have clear research evidence to support them and check how they have been developed.  There are a lot of “gurus” out there but their programme claims may do more harm than good.