Prebiotics are considered by some to be non-digestible carbohydrates, that are not digested by the body but nourish the micro-organisms in the colon. They occur naturally in the diet and are found in foods such as garlic, bananas, oats, onions and leeks. This idea has been criticised by some due to its poor definition and some scientists prefer to use the term 'microbiota accessible carbohydrates', as they are fermentable dietary fibre that the microbes can use. However, foods containing prebiotics are also the components of a healthy diet and should therefore be consumed regularly.
There are a number of components that negatively affect gut bacteria including lifestyle factors such as smoking and high stress levels, as well as the use of antibiotics.
Designed to fight infections, antibiotics reduce and deplete the natural bacteria living in the gut. Resistance to antibiotics is becoming a serious problem worldwide and it is for this reason that we should only take these when absolutely necessary.
Stress can change the number and diversity of our gut bacteria, which in turn affects the immune system and may explain why certain conditions, such as eczema or acne, flare up when we are more stressed.
A long-term reduced intake of fermentable carbohydrates for the treatment of IBS (as in a low FODMAP diet) can also negatively affect the bacteria in the gut. It is therefore important that these foods are only omitted for a specified time under the guidance of a specialist dietitian as the implications of long-term avoidance needs further research.
Generally, probiotics are safe for healthy individuals, however those with a compromised immune system may be at risk and should seek advice from a specialist dietitian or GP before starting.
Unless stated differently by manufactures, probiotics should be taken for a minimum of four weeks before effects may be seen. If no improvement is noted, it is recommended that you try another brand or stop completely.