What are probiotics and prebiotics – and do I need them?
Your intestines host a community of diverse bacteria to make up your gut microbiome. Probiotics and prebiotics are said to help to keep it healthy – but do they work?
What are probiotics?
You may have seen yoghurts or yoghurt drinks that contain probiotics on the supermarket shelves. These live cultures and yeasts are also available as supplements – and are frequently described as ‘good’ or ‘gut-friendly’ bacteria. The belief is that probiotics boost the number and variety of good bacteria in the colon, to help your digestive and possibly general health. Fermented vegetables such as kimchi (Korean pickled cabbage) and sauerkraut, miso and kefir (a fermented milk) are also naturally rich in probiotics and have become go-to health ingredients in recent years.
Do I need them?
Possibly. Probiotics may be useful for people who’ve been prescribed a course of antibiotics, which work by wiping out the bad (as well as some of the good) bacteria in your body as they fight infections. There is a fair bit of evidence that taking high doses of some probiotics can help prevent antibiotic-associated diarrhoea in children1 and reduce the risk of developing certain infections in adults2. Your doctor can advise you on this. Some people with IBS (irritable bowel syndrome) also report anecdotally that they find taking probiotics beneficial for reducing flatulence and bloating.3
Probiotic foods are generally fine for most of us and are a healthy addition to the diet, and people with a healthy immune system can usually take probiotic supplements without side effects. However, if you have any health issues that may mean your immune system is compromised, it’s best to check with your GP before introducing a supplement to your diet. Also, as probiotics are classed as food rather than medicine, their effectiveness is less well established, as they don’t have to undergo the same robust testing that medicines do3. Some small studies have shown that many of the bacteria in some probiotic products (mainly probiotic drinks) on the market are killed by our stomach acid and don’t even make it to our intestines4.
What are prebiotics then?
Prebiotics are non-digestible foods that stimulate the growth or activity of beneficial bacteria in the intestines. (The idea is that they provide the food that the probiotics need to thrive.) Examples are Jerusalem artichokes, leeks, onions, garlic, asparagus, bananas, legumes, honey, oats and lentils.
What are the benefits of these?
As well as the suggestion that they help ‘good’ bacteria to thrive, some studies have shown that prebiotics help our absorption of certain minerals5 and can also be helpful in combating IBS6. Fibrous vegetables and grains will also help keep the bowels regular, so prebiotics are generally helpful for a healthy diet. That said, some people may experience bloating or flatulence if they suddenly add lots of these foods to their diet.
Although there is still a need for more robust scientific testing on the influence of probiotics and prebiotics on our health7 (especially in supplementary form), anecdotal evidence points to benefits for some. However, there is no doubt that eating a varied diet, including a wide range of vegetables and fruit, is usually a very good idea.