The intestinal tract is the organ in the body that digests and absorbs food. It is populated by trillions of bacteria that are required for keeping the body healthy. These bacteria can be affected by a number of aspects including antibiotic use, a diet low in fibre, fruit and vegetables and infective diarrhoea. When this occurs, probiotics can help to reset the balance.
What are probiotics and how do they work?
Probiotics are living organisms that are found naturally in foods such as yogurt, kimchi, sauerkraut, miso and kefir. They are known as ‘good’ or ‘friendly’ bacteria as they compete for space and food against harmful bacteria and prevent them from settling in the gut.
What are prebiotics and how do they work?
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.
What can negatively affect gut bacteria?
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.
Excessive alcohol consumption can be inflammatory and may affect the lining of our digestive system, where a lot of our microbiome live, reducing them in numbers and therefore affecting our health.
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.
Smoking also has a negative impact on the bacterial composition of the gut in addition to the well documented health risks it carries.
What are the different types of probiotics?
There are numerous types of probiotics and each has different characteristics. They may be combined with others or appear on their own in powder, tablet or liquid dietary supplements. At the moment, foods that naturally contain probiotics are not eaten regularly in the UK and supplements are becoming more popular. The most common probiotics include lactobacillus acidophilus and bifidobacterium. These differ as they are made up of different types or strains of bacteria, and are recommended for different clinical conditions. Lactobacillus acidophilus have been clinically shown to lower the incidence of antibiotic-associated diarrhoea and can also result in a shorter length of stay in hospital for some. In order to experience this benefit, a vast quantity of food containing probiotics would need to be consumed. It is therefore easier and more effective to take a recommended probiotic supplement.
For those with a diagnosis of IBS, supplements containing bifidobacterium have been shown to reduce symptoms, including bloating, cramping and stool frequency, and can be taken for up to eight weeks.