Seeing a lot of talk about the importance of gut health? These are the latest findings, including those on food and supplements
Weighing in at nearly two kilos, our gut bacteria seem to play an even bigger role than was previously thought. These bacteria can influence our mood and act as a communication centre. Gut microbiota researchers Åsa Håkansson and Frida Fåk Hållenius at Lund University in Sweden share their latest insights.
Just 10 to 15 years ago, the idea of discussing our gut bacteria with our friends probably seemed odd. Today, it is no longer strange to talk about anti-inflammatory diets, prebiotics and probiotics, gut-brain axis, home fermentation and other related topics, at least among the health conscious.
Researchers have also made significant headway in understanding the importance of our gut microbiota.
"There is an explosion of new knowledge in this area right now. At the same time, there is a lot that we still don't know," says Åsa Håkansson, associate professor at Lund University, who has been researching the relationship between our gut microbiota and diet for several years.
Communicating with the whole body
Overall, it has become increasingly clear that the role of our gut microbiota is not just to digest food so that the body can absorb nutrients.
It can also be considered as something of a communication centre. When gut bacteria break down food, they produce satiety hormones and other substances that send signals to other parts of the body via the nervous system or bloodstream. These bacteria can also communicate directly with, for example, white blood cells in the blood or the lymphatic system. Tellingly, around 80 per cent of the immune system is located in and around the gut.
In line with this, our gut microbiota can also signal disease. For example, people suffering from Alzheimer's disease and diabetes have been found to have an abnormal bacterial composition in their gut. Studies are ongoing to identify causal relationships and to determine whether diet can prevent or at least mitigate symptoms.
Affecting our mood
According to Frida Fåk Hållenius, our gut microbiota can also influence our mood.
"As much as 90 per cent of the body's serotonin is produced in the gut. This hormone regulates our mood and sleep, among other things. Conversely, stress and sedentary behaviour can impair our gut microbiota, while exercise and mental wellbeing can improve it."
Studies are underway to identify the relationship between diet and serotonin levels to see if diet also has an impact via our gut microbiota.
More recent studies have shown that our gut microbiota also interacts with organs other than the brain, such as the lungs, as our gut flora appears to influence immune responses in the lungs.
Rapid development
In general, there is "a large number" of scientific studies being published on the gut microbiota and probiotics right now, according to the two researchers. One contributory factor is the rapid development of technology, which enables extensive data analyses.
Are there other interesting findings? Absolutely, according to the researchers - more exciting insights are outlined below:
Our gut microbiota is both unique and adaptable
In the past, it was thought that radically changing our gut microbiota was quite simple. Recent studies have shown that it actually stabilises in early life, based mainly on environmental factors and lifestyle, but our genes also seem to play some role. In other words, we have a basic gut microbiota that we carry with us throughout our lives.
"The first transfer of microorganisms to the infant occurs mainly at birth. The infant is then colonised by the mother's intestinal and vaginal flora and microbes in the surrounding environment. Depending on which genes you have, each individual has their own unique gut microbiota," explains Åsa Håkansson.
The composition of the flora then gradually evolves in the infant and remains relatively stable in adulthood, but its composition is greatly influenced by the food we eat and the lifestyle we lead. As we get older, our gut microbiota changes and so does our immune system.
Improving your gut microbiota is easy
If you change your diet, your gut microbiota a will change quickly. But if you stop eating what changed your gut microbiota, it will often return to its original state.
In a study by Anne Nilsson, Olena Prykhodko and Frida Fåk Hållenius, among others, participants were asked to swap white bread for rye bread for one evening sandwich. The very next morning, their gut microbiota demonstrated a rapid improvement with higher levels of the bacterium Faecalibacterium prausnitzii, which has been shown to have anti-inflammatory effects. Rye bread also increased the amount of Prevotella in the gut - a bacterium with favourable effects on blood sugar regulation.
Good food is even better for some people
Healthy food is good for everyone, but recent studies have shown that some people gain even better health benefits depending on their gut bacteria. This means that, for example, an apple may be even better for you than for your neighbour, while your neighbour may gain more health benefits from eating legumes than you do.
"In this case, the reason may be that your neighbour lacks a certain bacterium that is particularly good at breaking down carbohydrates in apples. Our gut microbiota plays a major role in how we absorb nutrients."
In the future, we may be able to get individual dietary advice to maximise positive health effects. But research has not got that far - yet.
Links with mental health conditions
Studies show that people with for example ADHD and schizophrenia have a different, and sometimes worse, gut microbiota. This chicken-and-egg situation, i.e. what the causal link is, remains unclear. However, there are actually several studies showing that mice genetically treated for developing autism can regain their social skills and exhibit reduced anxiety and stereotypic behaviours when their gut microbiota is improved with lactobacilli and bifidobacteria.
"Humans are also being studied to see if different types of bacteria can alleviate symptoms of autistic functional impairment, but the human gut microbiome is far more complex than that of mice, so more research is needed before an effective treatment can be established," says Frida Fåk Hållenius.
There are also several ongoing clinical trials investigating whether diet and the gut microbiota can alleviate depression, including exploring the relationship between diet, flora and serotonin levels.
Huge variation in what a healthy gut microbiota looks like
Broadly speaking, healthy people have the same groups of gut bacteria, but they may differ at the species level. The role of different species is not yet fully understood. However, we know that diversity is a good thing. In an unbalanced flora, diversity has fallen sharply and there are no longer good bacteria to block the growth of bad bacteria.
Supplements: to take or not to take?
Probiotics have become popular supplements - usually species and strains of lactobacilli and bifidobacteria - in the hope of giving your stomach a boost. Probiotics are taken either as food supplements or in the form of foods containing these live microorganisms, such as fermented vegetables. Does taking these help?
"There is a huge variety on offer here! But not all of them are backed up by scientific evidence. If you're going to buy products, you should choose those rooted in science in some way. It can absolutely have some effect, as even a perfectly healthy person needs to nurture their own gut microbiota," says Åsa Håkansson.
Health claims on products ensure that there are scientific studies to back them up, which have been reviewed by independent experts.
"If there are no health claims, you can google the bacteria in the product and see what evidence there is. This can be both food, such as yoghurt, and pills containing bacteria."
