Amy Loughman, PhD
5 facts about probiotics and prebiotics
Updated: Jan 9, 2020
This week I attended a 5-hour workshop on the microbiome with about 40 other clinicians, researchers and thought-leaders. Expertise ranged from diet, Crohn’s disease, IBS, sleep, chronic fatigue and even water quality (this field is broad!). I’ve listed 5 of the key ideas that I’ll be taking away from this meeting.
An important caveat to everything written below is that the science is still at a stage where many views are still opinions, and there are more questions than answers. I don’t want to shy away from this, or pretend that it simple. When you try to get to the bottom of things, it is mind-explodingly complex.
Dr Jane Muir of Monash University talking about prebiotics, 6th October 2016.
1. We still don’t know exactly what a ‘healthy microbiome’ is. So far, much of the science has examined the gut microbiota of people with diseases. Much less has looked at health, or wellness. Even amongst people who are healthy, there is a fair bit of variability.
2. It is still anyone’s guess which probiotics are good for you. In fact, some may even be harmful. Sorry to anyone taking a daily probiotic supplement. The term ‘probiotic’ specifically means bacteria that is good for you. But unfortunately, it’s very hard to pin down which those particular bacteria are. See, bacteria live in a community, with approximately 1000 different species with 5 million genes in the human gut (with only 14 species that are thought to be core to most people!). And there’s only so much room down there. So sending a large army of one particular bacterial species into the community (say, lactobacillus), could annihilate some other species.
3. Just on lactobacillus, which is many people’s favourite probiotic (it is in many commercial probiotic supplements) only makes up a small proportion of most adult gut bacteria. It’s more common in kids. So it’s not yet clear that it confers benefit for most of the people taking it…
4. As well as probiotics, we have prebiotics. PRObiotics are actually bacteria that are taken to introduce that specific species into the gut. PREbiotics are substances that stimulate the growth or survival of ‘good bacteria’. You do not need a supplement to get prebiotics into you — they are found inmany common foods. These include split peas, leeks and pumpernickel bread but also watermelon and cashews.
5. Prebiotic supplements haven’t shown direct health effects. This could be because people are already getting prebiotics naturally though their diet. Basically you can max out on them — getting more is unlikely to be better. To use a simple example, if the daily recommendation is the consume 1.5L of water/day, doubling that probably won’t be doubly as good (you’ll just be peeing all day).
So in short, probiotics and prebiotics are important contributors to your healthy gut balance. However scientific jury is still out on supplementation.The best advice so far is to keep your diet varied and naturally full of foods rich in probiotics and prebiotics. Fermented foods such as sauerkraut, kimchi, sourdough and kefir are probiotic. Carbohydrate sources with dietary fibre are prebiotic.