Question 1

What is the difference between prebiotics and probiotics?

There seems to be a lot of talk about prebiotics helping eczema at the moment, and they seem to be making it clear that prebiotics and probiotics are not the same.

Answer

Prebiotics and probiotics are not the same, but they are very close.

Let’s start with Probiotics. These are ‘friendly gut bacteria’ - usually species of Lactobacilli similar to those found in milk. Probiotics have been shown to be helpful for preventing and reducing the severity of gut infections.

Interest in probiotics and eczema developed because of the hygiene hypothesis. Basically, the hygiene hypothesis suggests that we are ‘too clean’ these days. The theory came from the observation that eczema and hay fever are commoner in first born children than in subsequent children. Eczema has also been shown to occur more in children living in smaller families. The theory suggested that children born into larger families get more infections from other family members, and these infections seem to protect the child from developing allergic disease. In other words, the immune system has got something better to do ie fight external infections, rather than developing allergies to common things in the environment which don’t really do us any harm. Numerous studies have found that children growing up on farms and other ‘dirtier’ environments get less allergic disease than those brought up in towns. Research from Sweden has shown that the composition of the gut bacteria is very different in children with allergic disease than in those who do not develop conditions like eczema. Researchers therefore thought that by giving probiotics them to a new born baby at higher risk of developing allergic disease (ie their parents had either eczema, asthma or hay fever), the baby’s gut would becomes colonised with ‘friendly’ bacteria which then help to protect the body against developing allergic disease. So that’s Probiotics.

Prebiotics on the other hand are not live bacteria, but a combination of nutrients that help to make your own ‘friendly’ bacteria grow in the gut. They are non-digestable and usually made up of something called oligosaccharides. Prebiotics and probiotics basically do the same thing. Prebiotics help to ‘fertilise’ your own friendly gut bacteria, and probiotics add them directly to the gut.

Now the question is, whether probiotics or prebiotics are helpful for eczema. We have to consider this question in two parts: (i) are they useful for preventing eczema from developing in the first place? And (ii) are they any good for treating eczema once it has become established in a child?

Eczema prevention

Two large systematic reviews (reviews that have been done in a systematic way) last year found some evidence to support the use of probiotics in preventing eczema to infants born to parents with allergic disease. The included studies mainly dealt with giving probiotics to mothers in the last 3 months of pregnancy, and the probiotics used were usually Lactobacillus rhamnosus GG. Overall, the studies have suggested that giving probiotics in this way may reduce eczema in the children by around 30%. There is still some doubt about these findings since the benefits are smaller in the larger better quality studies and some studies published since the review was done have not shown the same benefits.

Another systematic review of prebiotics for preventing eczema found only two studies – one showed benefit and one showed no difference, There just isn’t enough evidence to say either way if prebiotics are helpful in preventing eczema at the moment.

Eczema treatment

Here we are dealing with giving probiotics or prebiotics to a child who already has eczema. This question has been looked at very thoroughly in a systematic review of 12 randomised controlled trials (fair test) involving 781 children. When all the studies were added together, there was a very small reduction in eczema symptoms in those taking probiotic treatments. But the difference was very small– probably too small to be noticed in real life. There is still a possibility that some varieties of lactobacilli are more effective than others, but it has not been shown convincingly yet. There is therefore no convincing evidence that probiotics produces a clinically useful benefit in established eczema right now, but new studies using different strains could suggest otherwise, so we will have to wait until these other studies have been done before deciding one way or the other. At the moment, there are no good studies looking at prebiotics in treating established eczema, so we can’t say if they are useful or not helpful.

Sorry to end on such a dull note. At a personal level, I was particularly interested in probiotics (and prebiotics) because of their low potential for side-effects. The bottom line at the moment is that they don’t appear to be effective for children who already have eczema, but they might be helpful to prevent eczema in a newborn if you (as a parent) have allergic disease.

If you want to read more about the systematic reviews of probiotics and prebiotics for prevention of eczema, go to http://www.library.nhs.uk/skin/ViewResource.aspx?resID=306734&tabID=289 and if you want to read more about probiotics for treatment of eczema, go to http://www.library.nhs.uk/skin/ViewResource.aspx?resID=322682&tabID=289&catID=8310