Probiotics

Written by: 
Dr Sarah Brewer

Have you heard of probiotic yoghurts and wondered what the benefits are? This page gives the answers.

Probiotics are live bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. and yeasts that provide various health benefits, provided that your body obtains them in sufficient amounts. They are found in some fermented foods such as bio yoghurts, and in supplements taken as capsules, tablets or powders.

The name probiotics combines the Latin pro (for) and the Greek bio (life) to describe substances that are beneficial for life. Those bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. that can provide health benefits are popularly called 'friendly bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell.'.

Only a few types of bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. have proven benefits for health. Nevertheless dietary sources of probiotics Dietary supplements containing bacteria believed to be necessary for proper gut function.- such as bio yoghurts, milk-based drinks and fruit juices with added friendly bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. - are extremely popular: as many as 20 billion doses of probiotics are consumed worldwide every year.

The most common probiotic organisms are lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. (LAB). These include strains of Lactobacilli and Bifidobacteria. They are acid-tolerant and so many survive passage through the stomach to reach the large intestines. There, the most beneficial probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. stick to landing sites on the intestinal wall and colonise the colonThe large intestine..

Below we cover the benefits of, uses for and concerns about probiotics:

Probiotics and the gastrointestinal tract

Probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. play an important role in maintaining a healthy balance in your intestineThe section of gut, or gastrointestinal tract, from the stomach to the anus.. They work in several ways, including the following:

  • They secrete natural antibioticsMedication to treat infections caused by microbes (organisms that can't be seen with the naked eye), such as bacteria. known as bacteriocins
  • They stimulate production of natural antiviralA substance that acts against viruses, for example and antiviral drug. substances such as interferons
  • By producing lactic and acetic acids, they discourage the growth of potentially harmful bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell.
  • They limit the spread of harmful bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. and yeasts by competing with them for available nutrients
  • They compete with other bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. for attachment sites on intestinal cellThe basic unit of all living organisms. walls, literally crowding the other bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. out so they pass through the intestines without gaining a foothold.

Lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. produce short-chain fatty acids, which reduce flatulence and act as a major energy source for cells in the lining of the intestineThe section of gut, or gastrointestinal tract, from the stomach to the anus.. The short-chain fatty acids are also absorbed from the colonThe large intestine. and transported to the liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats., where they have a beneficial effect on cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy. metabolismThe chemical reactions necessary to sustain life..

Probiotics and diarrhoea

Some lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. can inhibit the growth of harmful bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. such as Salmonella, Shigella and Clostridium, which cause gastroenteritis, leading to diarrhoeaWhen bowel evacuation happens more often than usual, or where the faeces are abnormally liquid..

Tip: If you are travelling abroad, consider taking probiotics before, during and after your trip to help protect against gastroneteritis.

Sometimes you may suffer from diarrhoeaWhen bowel evacuation happens more often than usual, or where the faeces are abnormally liquid. when you're taking a course of antibioticsMedication to treat infections caused by microbes (organisms that can't be seen with the naked eye), such as bacteria. because the antibioticsMedication to treat infections caused by microbes (organisms that can't be seen with the naked eye), such as bacteria. have the effect of reducing levels of natural lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. within the intestines. Taking lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. probiotics helps to prevent this form of diarrhoeaWhen bowel evacuation happens more often than usual, or where the faeces are abnormally liquid..

Probiotics and Helicobacter pylori

Probiotic organisms can inhibit Helicobacter pylori - a type of bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. that infects the stomach lining to cause inflammationThe body’s response to injury. (gastritis), peptic ulcerationAn ulcer caused by the erosion of the lining of the gastrointestinal tract by digestive juices. and possibly stomach cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body..

The standard treatment for H. pylori infectionInvasion by organisms that may be harmful, for example bacteria or parasites. is a 14-day regime of antibioticsMedication to treat infections caused by microbes (organisms that can't be seen with the naked eye), such as bacteria.. Adding probiotics to this treatment seems to improve the eradication rate by 5 - 15 per cent.

Probiotics and irritable bowel syndrome

Changes in the normal balance of bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. in the bowel have been linked with several conditions, including irritable bowel syndrome (IBS).

Taking probiotics will boost the number of lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. in your bowel, and this can reduce unpleasant symptoms of IBS when used alone or in combination with standard anti-spasmodic medications. This is probably because the lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. reduce the presence of gas-producing enterobacteria that are associated with symptoms of IBS.

Probiotics and inflammatory bowel disease

Probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. may improve symptoms associated with Crohn's disease and ulcerative colitis but this has not yet been definitely proven.

Probiotics and lactose intolerance

Lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. can ferment milk sugar (lactose) and convert it to lactic acid. For this reason, they might be expected to improve symptoms associated with lactose intolerance.

Some trials have shown a benefit, but others have not. A review of the evidence concluded that in general probiotic supplements do not appear to help people who have lactose intolerance.

Other health benefits of probiotics

Urinary tract infections are linked with bowel bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. that find their way into the bladderThe organ that stores urine.. By inhibiting these bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell., probiotics may help women experiencing recurrent urinary infections. Most research shows encouraging results, but this is not yet definitely confirmed.

Similarly, probiotic lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. naturally found in the gut are believed to inhibit the growth of yeasts responsible for vaginal Candida infections (thrush). A recent study shows that taking both probiotics and the antifungal drug fluconazole can significantly improve the effectiveness of the treatment, reducing discharge and limiting the presence of yeasts.

Probiotic supplements may also reduce the development of allergic conditions such as eczema by stimulating the production of antibodiesSpecial proteins in the blood that are produced in response to a specific antigen and play a key role in immunity and allergy. rather than allergic reactions. As a result, probiotics appear to reduce the development of eczema during at least the first 4 years of life.

Selecting a probiotic supplement

Dietary sources of probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. include live bio yoghurts, fermented milk drinks, capsules, powders and tablets. They are available in supermarkets, pharmacies and healthfood stores.

Consider choosing a supplement that supplies a known quantity of probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell.. A suitable quantity is 1 - 5 billion colony-forming units (CFU) per dose.

Some supplements are enteric-coated. This process improves the survival of probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. as they pass through the stomach. Enteric-coated supplements can contain a smaller quantity of probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. and still provide beneficial effects. A suitable quantity in this case would be 10 million freeze-dried probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. per dose.

Tip: You may want to check the shelf life of the supplement. Those close to their expiry date will contain fewer live probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. than those with longer remaining until the end of their shelf life. It is important to check whether the supplement needs to be refrigerated. Supplements containing freeze-dried bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. held in suspended animation do not need to be kept chilled.

Safety

Taking oral probiotic supplements appears to be safe. Few side effects are reported.

Tip: Probiotic supplements have been used in clinical trials involving people with reduced immunity. It is important to ask your doctor's advice if you are intending to give probiotic supplements to a pregnant woman, an infant or someone with intestinal bleeding, pancreatitis, HIV infectionInvasion by organisms that may be harmful, for example bacteria or parasites. or cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body..

In summary

Many probiotic strains are commercially available. Some have good evidence to support their claims of health benefits, but others do not.

More research is needed. The World Health Organization is introducing guidelines regulating probiotic production, clinical trials and labelling.

Prebiotics and synbiotics

Prebiotics are non-digestible food ingredients that selectively stimulate the growth of probiotic bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. in the colonThe large intestine.. They cannot be used as a food source by other less beneficial bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell..

Prebiotics include substances known as fructo-oligosaccharides (FOS), which are found in foods such as oats, barley, wheat, garlic, onions, bananas, honey and tomatoes.

Tip: It is important to seek the advice of your doctor before giving probiotic supplements to infants. Your doctor will advise you only to use supplements specifically designed for the infant age group. It may be better to stimulate growth of the child's natural lactic acid bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. through the use of prebiotics, which are now added to some baby-milk formulas.

Probiotics and prebiotics are now increasingly used together, a combination known as synbiotics.