What’s the difference between prebiotics and probiotics?
Have you noticed that every other food and drink product seems to contain either prebiotics or probiotics?
There has been a huge surge of public and research interest in what’s going on at the microscopic level in our guts. Apparently, we’re all bloating, gassy and intolerant to everything and it’s our guts that are to blame. Our guts are filled with microscopic creatures (mostly bacteria), around 100 trillion of them in fact, just trying to do their job, but they are supposedly being upset by our terrible diets and lifestyles and need help to rebalance themselves. We want to keep them happy as they play a vital role from helping metabolise nutrients from food and supporting our immune system, to producing vitamins and playing a role in defence against disease. So, in come probiotics and prebiotics to the rescue. But just what are probiotics and prebiotics, and do we really need them?
Probiotics are living bacteria and yeasts — they’re often added to yoghurt drinks. They also occur naturally in kefir and foods like yoghurt and fermented cabbage (such as sauerkraut or kimchi). Probiotics are thought to help restore the balance of your gut bacteria when it has been disrupted, for example through ill-health or use of a particular medication, like antibiotics. Prebiotics are non-digestible plant fibres that nourish the friendly bacteria in your gut. They are found in many plants and vegetables. It’s true that we need to try and maintain a healthy gut as evidence is emerging all the time about the importance of the gastrointestinal microbiome for so many aspects of our health. However, it is not clear whether ingesting prebiotics and probiotics for this purpose is effective.
There are a number of questions over the use of probiotics. There are hundreds of different species of gut microbes, and products range in the strains of bacteria and yeasts they contain, so are we getting the right ones? The thing is, we don’t yet really know which ones we need. As individuals, we may need different types at different times. We’re also not sure how many different types we need or even how much of each, so we don’t know whether the products contain the right ones in the right amount to make a difference to us. If we knew whether we were lacking a particular type and how much we needed to replace it, that could offer a promising route to addressing the balance. But, even if we knew those things, it is not clear whether all the probiotics we consume necessarily survive the acid environment of our stomach to reach the gut to populate it.
Some research has found that while a small proportion do survive, to have the maximum effect on our health they need to stick our intestinal cells and there isn’t much evidence to suggest this is actually happening. And so, they aren’t multiplying when they reach our guts and are passing through into our faeces. As they aren’t sticking and multiplying, this means that you continually need to consume them to gain benefit. The effects appear to be transient, which is counter to the assumption that you are somehow boosting your colony of microbes.
Another consideration is that for those who are well and already have a healthy lifestyle, we don’t know whether we gain any additional health benefit from consuming probiotics, especially when our bodies already have a good internal regulatory system. After all, what we might consume is just a tiny fraction of the numbers naturally produced in our guts. Just as there are different types of probiotics, there are also different types of prebiotics that are selectively used by different gut microbes. So, if you don’t know which microbes you have that need enriching, you won’t know what prebiotic to take that might help.
For a moment let’s say they do make it into our guts, the real question is — do they work? A small amount of data from clinical trials support the use of probiotics in some people who already have other health issues, but there’s not yet a good case for proactively taking them to prevent ill health. Scientific findings on the effects of prebiotics are sparse and ensuring you consume lots of diverse fibre sources from fruit and vegetables is probably more effective. Dietary fibre appears to strongly influence our gut microbiome and is better related to our health than probiotics or prebiotics.
As usual, while it might not be popular advice, the key is to eat a well-balanced and varied diet. In fact, given the variation in the gut microbes between individuals and the importance of food on gut health, research is taking place to investigate whether what we all really need is our own personalised diet tailored to our gut. This could be the future we should aim for rather than more and diverse wellness products that are likely to contain only a fraction of the probiotics found in the pharmaceutical-grade supplements that have shown promise in clinical trials.
