What is the microbiome?

Did you know that there are as many microorganisms living inside and on you as there are cells in your entire body?  That means that half of your body is made up of other living beings – microorganisms – which are so small that they can only been seen through a microscope. Microorganisms include bacteria, fungi, protozoa, algae and viruses. They live in and on different parts of your body but most of them are in your digestive tract (gut) and most of the microorganisms in the gut that affect your health are bacteria. Collectively, all these microorganisms are called the microbiome (or microbiota) and recent research indicates that the microbiome has a huge impact on your health!

Everyone’s microbiome is unique to them with different numbers and types of microorganisms; some of which are good for you and some are not. There is still so much we don’t know about the microbiome but this article will discuss how the it affects our health and what you can eat to improve your own microbiome.

The microbiome and our health

Many different factors affect your microbiome including how you were born (e.g. by caesarian), whether you live with other animals, lifestyle factors, such as diet and exposure to toxins, use of antibiotics and other medicines and stress. These factors affect both the number of bacteria, the types of bacteria and the diversity (how many different species there are).  Everyone’s microbiome is different and there is now research looking at how different foods could be used with different people to improve their health.

The bacteria and other organisms in the gut depend on us for their survival but they also give us something back, as long as they are healthy and there is a good variety of bacteria. Some bacteria that live in our gut are good for us, some don’t have any effect and some are not so good for us. The ones that are good for us can do lots of different things, for instance:

• Produce nutrients such as vitamin K and some of the B vitamins.
• Digest some types of fibres to produce short chain fatty acids and gases which fight a number of diseases (more about these later).
• Produce chemicals that inhibit the growth of other microorganisms that cause disease e.g. Clostridium difficile and E. coli.
• Produce other chemicals that interact with the nervous system or reduce levels of inflammation in the body.

There are many different ways in which we think the microbiome helps to prevent disease. For instance, it is particularly important for a healthy immune system. The body interacts in a complex way with the microorganisms in your gut to improve your immune response to infection so that you can fight off the invading bacteria or viruses without fighting your own cells and organs.

Some species of bacteria in your gut produce chemicals called short chain fatty acids which are vital in tackling a range of diseases. For instance, one of these short chain fatty acids called butyrate provides energy for a type of human cell that destroys cancer cells. Butyrate also helps to regulate glucose levels. Another short chain fatty acid called propionate regulates the body’s feeling of fullness after eating. Acetate, another short chain fatty acid, regulates cholesterol in the blood and again may help to regulate appetite.

Some microorganisms produce chemicals which produce an inflammatory effect in the body whilst others produce an anti-inflammatory effect. Inflammation is linked to a wide range of diseases such as heart disease, diabetes and cancer.

There is increasing evidence that the microbiome is linked to a healthy brain and to your mental health. For instance, research suggests that eating certain foods can improve your feeling of well being and a healthy microbiome is involved in the production of the brain hormone serotonin which helps to stabilise your mood and make you feel happy.  Other research suggests that conditions such as Alzheimer’s and Parkinson’s are more likely in people with an unhealthy microbiome.

Unhealthy bacteria produce chemicals which help to cause disease, such as a chemical called TMAO which raises the risk of heart disease. TMAO is produced by the bacteria in the gut when you eat animal products, so vegans are at an advantage here.

The microbiota may also play a part in the development of obesity. People who are obese have different microbiota from healthy weight people. In fact, recent trials have taken place to assess whether transplanting microbiota from the gut of a healthy person into an obese person can improve their recipient’s microbiota, although the findings have so far been inconclusive.

At present research indicates that the microbiome is also linked to a range of other conditions and diseases such as autism and allergies. Sadly, many of the studies that show these links have been done on mice and it isn’t clear how the findings translate to humans.

What can you do to keep your microbiota healthy?

Foods which produce an unhealthy microbiome are processed foods, foods high in sugar, alcohol and animal-based foods. So, the key is to reduce these and increase healthy foods which are those that your beneficial bacteria need to survive. These foods are carbohydrate rich plant foods and are collectively called prebiotics. This means a varied plant-based diet with a wide range of unprocessed vegetables, fruits, nuts and pulses; these all contain the fibre which your healthy bacteria love. Research shows that the greater the variety of food eaten, the better the diversity of the microbiota. If your diet is currently low in plant foods, build up the amount of fibre slowly so that your gut bacteria have a chance to adapt.

In addition to prebiotics, research also suggests that probiotics may be useful. These are foods which already include the healthy live bacteria, such as Lactobacillus, in them. Probiotics are fermented foods such as sauerkraut, kimchi, kombucha and live (plant-based) yoghurt. Other foods may contain probiotics, such as tempeh, miso and some nut cheeses.

To summarise, eat lots of different types of mainly unprocessed plants and include a variety of plant-based probiotics.

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Words by Liz Readle, Certificate in Plant-based Nutrition, University of Winchester

Image by Geralt via Pixabay