Did you know you have ten times more bacteria in your gut than human cells? Millions are being spent on research to uncover its crucial role in health and disease

The microbiome is big news in health this year. Fortune Magazine has declared 2015 The Year of the Microbiome, and there is significant research going on to fully understand its complex relationship to health and disease, notably the multimillion-dollar five-year Human Microbiome Project.

But what is it? And why is getting so much attention?

We have more bacteria in our body than we do human cells, up to ten times more. Most of them are in our intestines; we each have literally trillions of bacteria and fungi living in there. Scientists are increasingly realising the importance to our health of this human ecosystem.

Our microbiome is essential for human development, immunity and nutrition. It helps to digest our food, regulate our immune system, protect against other disease-causing bacteria, and produce several vitamins including B vitamins.

However, imbalance in your microbiome can contribute to chronic illnesses of the gastrointestinal system such as IBS and Crohn’s disease. It may influence your susceptibility to infectious disease, and certain collections of microbes may determine how you respond to drug treatments.

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Time and money – a lot of time and money – is being devoted to studying in detail these microbes that live in the human body. Several studies over recent years have uncovered the structure of the bacterial microbiome and how it functions, both in its healthy state and in a variety of disease states.

In particular, the US National Institute of Health spent $173 million on its five-year Human Microbiome Project, to describe the microbiome, identify and characterise its microorganisms, and analyse its role. This enormous project is a roadmap for discovering the role of the microbiome in health, nutrition, immunity and disease.

And there is increasing evidence that the microbiome has an affect on the central nervous system and brain, affecting how we think, feel and act, and on the development on neurological conditions. In 2014, a major neuroscience symposium called this work a “paradigm shift” in brain science.

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Watch this TED talk by pioneering microbiome researcher Professor Rob Knight:

The organisms in our microbiome – bacteria, fungi, protozoa and viruses – live on and in our bodies but, though they may sound rather unsavoury, think of them as helpful and welcome colonizers rather than invaders. They start to colonize us at birth, and come from the food we eat and anything else that gets into our mouth, like pollution, putting your hands to your mouth, etc.

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The exact types and combinations of organisms in our bodies is constantly changing, over months, weeks and sometimes daily. Different ones exist in different parts of our body, some of them temporary residents, some passing through, and some more firmly embedded.

They travel around between different systems in the body, between people living in the same house, and between ourselves and the various environments we come into contact with each day.

However, over time, disease-causing microbes accumulate. They affect our metabolic processes and even our gene activity, causing an abnormal immune response against the body’s normal tissues and substances.

Health conditions and microbiome dysfunction

Such dysfunction is associated with conditions including inflammatory bowel disease, obesity, Crohn’s disease, malnutrition, and autoimmune diseases such as type 1 diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis and fibromyalgia.

Autoimmune diseases are now believed to be passed on in families not by DNA inheritance but by inheriting the family’s microbiome.

Genetic studies have linked various combinations of different species in the microbiome to certain health conditions. The evidence so far suggests that a balanced and diverse microbiome contributes to good health and a less diverse and less balanced microbiome to poor health.

In developed countries, we are likely to have less diversity in our gut flora. This means we can lack the resilience necessary for a strong immune system is linked to inflammatory conditions, leaky gut and autoimmune disease, and. Some research suggests the western diet of animal fats and high protein, stress and excess alcohol may be factors.

Microbiome research in Britain

The microbiome and issues surrounding it has become an area of huge medical interest and importance. Some of the questions being looked at include how it affects our nutrition; how probiotics and antibiotics affect it, and how it affects our reaction to drugs; and how research findings can be used in clinical settings.

If you would like to participate in research into microbiome profiling, a team at Kings College London is currently crowdfunding The British Gut Project, a scientific project to build and study a database.

Effect of diet on the microbiome

Research into how the foods we eat affect our microbiome is at an early stage. It is known that eating sufficient dietary fibre can help feed the beneficial bacteria, which in turn produce nutrients that nourish the cells that line our gut.

Too little fibre, on the other hand, can starve them, and when they’re starved of fibre they eat us: they gnaw away at the mucin (protective proteins) in the mucus lining in the large intestine.

A plant-heavy diet helps to increase diversity in your microbiome (yup, yet another reason to eat more vegetables – a lot more). Plants give the microbes something to chew on, break down, digest and extract nutrients from. It’s what they need to survive.

Another way is to eat fermented foods as they contain naturally occurring probiotics, which encourage the growth of essential bacteria in our gut and may help to prevent the bad bacteria from damaging our health. Researchers are still trying to understand why this is.

Despite all the hype this year over fermented foods, research is not yet certain whether their effect on the microbiome is permanent.

One microbiome researcher, Professor Rob Knight, says: “Epidemiologically there seems to be some evidence that eating fermented food is beneficial rather than harmful.” Another, Jeff Leach, says short-term dietary changes don’t have a dramatic impact.

Either way, the microbiome is a fascinating area of research, and one well worth staying informed on as future studies are published.

Jacqui Gibbons is the editor of High50’s health channel, edits beauty and lifestyle features, and writes about health trends. Twitter @Jacqui_Gibbons