Since ancient times, many cultures around the world have included foods rich in microbes – friendly bacteria able to give a helping hand to our microbiota and overall health – in their traditional diet. Scientists are starting to better understand the role of these microorganisms and how they can have a positive impact on the health of our gut.

At the beginning of July, a panel of experts on microbiota gathered in Barcelona at the Bdebate conference, held at the Cosmocaixa science museum. Of all the subjects under discussion, probiotics was one of the key issues, and Mary Ellen Sanders was one of the experts charged with addressing this topic.

Mary Ellen is currently working with the Global Alliance for Probiotics, a European collaboration of seven probiotic companies, which have joined forces to address issues related to health claims for probiotics in the EC. She was invited to join the scientific advisory board for the American Gastroenterological Association’s Center for Gut Microbiome Research and Education and also serves as Executive Director of the International Scientific Association for Probiotics and Prebiotics.

These days many foods and dietary products are labelled as probiotic. What exactly is a probiotic?

It is a live microorganism that must be administered in high enough quantities to provide a health benefit. You can either take the probiotic as a pill, in dried form, like a nutritional supplement, or it can be part of a food.

It is often said that traditional regional fermented foods such as kefir, kimchi or sauerkraut have long contained probiotics. Is that true?

There are various fermented foods like yogurts, cheeses, pickles and miso soup that contain live microbes, but to meet the definition of a probiotic they also need to show to be beneficial to health.

Is it healthy and advisable to add some probiotics to our diet?

I think we must differentiate between two situations: those who have a specific problem that they are trying to target with a probiotic, and also those who simply say, “I want to have the healthiest diet possible”. For people who have a particular problem it is important for them to look for specific microbes that have been studied for the condition they are trying to deal with, like irritable bowel syndrome or Crohn’s disease.

But if you are a healthy person with a good diet and you want to recreate your ancestors’ diet, based on the idea that human beings used to consume a lot of microbes, then you can include food with microbes. However, we don’t necessarily know what those foods are doing and why they are beneficial. The only thing we know is that when we eat foods rich in those microorganisms we can change our microbiota and that is associated with different types of benefits. For instance, we know these bugs play an important role in the functioning of our immune system and that they help our gut function properly.

Are there probiotics designed for specific issues?

There are, in fact, a couple of products tested for irritable bowel syndrome, where there might be some inflammation; probiotics have been shown to decrease inflammatory response and also decrease pain sensitivity. There are others that have been tested for travellers’ diarrhoea and others for acute diarrhoea. Also, they may help you recover after taking antibiotics, cope with the side effects and help get your microbiota back to normal. Also, they can have an impact on what you might call the ‘gut environment’ and thus encourage the production of certain fatty acids, reducing the pH so the gut environment is just that little bit healthier.

Can they be used as a treatment for the so-called modern plagues: obesity, diabetes, cardiovascular conditions?

In that field there is some really interesting research being undertaken and some studies that show that, for example, probiotics can help in hypercholesterolemia, as they can play a role in regulating the level of lipids in your blood. But in terms of obesity, there are lots of animal studies in which they change the microbiota of the animals through faecal transplants and they do influence whether the animal is obese or lean. Humans are always more complicated, however!

Microbiota has also been related lately to mental disorders, such as depression or autism. Do you think taking probiotic treatments for these mental disorders could become a possibility in the future?

Think about this: if you get really upset, you may have loose stools. Why? Because your brain is communicating with your gut. And it can also happen the other way round, with your gut affecting your brain. Autism, depression, anxiety… although I am sure none of the treatments for these mental conditions are going to be as simple as just ‘take a probiotic and you‘ll be fine’, I do think that microbes will probably play a big role. We need more in-depth research to identify the associations and see whether there is any causality. What we know now is that some changes in the patterns of microbiota are associated with autism, diabetes, obesity, Crohn’s disease, etc. What we don’t know is whether changes in microbiota cause these conditions, contribute or if they are just a result of them. So, does becoming obese change your microbiota? Or does your microbiota have an impact on the fact you are obese? There is evidence from animal models that it can be causal but studies on humans are not yet complete.

Lately, alterations in gut microbiota have also been linked to Parkinson’s, Alzheimer’s, depression, even AIDS.

It gets a bit crazy, doesn’t it? The gut is a very important organ. And for a long time we knew microbes were there but only in the last 6-7 years of research have we really started to appreciate the role they play. That is when we realised just how dynamic the relationship between humans and microbes really is. Before, we used to think that microbes were there causing problems and we took antibiotics to kill them. That was until we realised that they communicate with human cells and vice versa, and that there is a lot that is going on. I think it is a really exciting new field and new findings will shed some light on the incredible importance of this long ignored organ.