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We live in a close relationship with the bacteria that are on us, and inside us – and while we usually think of bacteria as harmful, there are in fact countless different bacteria that help us. You may feel slightly queasy thinking that around 100 trillion bacteria are living on and inside your body right now – in fact, you’re made up of 10 times more bacterial cells than human cells! Some live on the
surface of your skin, inside your mouth, nose and vagina – but the biggest number are living inside your gut, particularly your colon. The gut flora – also called the gut microbiota – refers to the community of bacteria living inside your digestive tract.

This article was included in issue 80 (spring 2019) of The Menopause Exchange newsletter.

Around 1,000 different bacteria are known to live in the human gut, but everyone typically has only around 150 at any point in time. What’s fascinating is that we all have a completely unique gut flora, and as there are so many different possible combinations of bacteria, it appears that no single combination can be the ‘optimal healthy gut flora’ – what’s perfect for me won’t be perfect for you.

What does the gut flora do?
Gut bacteria help with digestion, breaking down parts of food that your stomach and small intestine are unable to digest (e.g. dietary fibre), helping to neutralise harmful by-products of digestion and adding bulk to your stools. They use undigested food waste as an energy source and ferment this to produce useful byproducts, including vitamins (B2, B12, folate and vitamin K) which you absorb and use, and short-chain fatty acids, plus some less useful by-products such as gas.

Gas production in your digestive tract is perfectly normal, usually harmless, and disposed of by passing wind – typically between five and 15 times each day. The balance of bacteria in your gut, coupled with the types of food you eat dictates how much gas you produce. According to a research study, people with troublesome flatulence aren’t necessarily producing more gas, but have an imbalance of bacteria that means they have a lower tolerance of the gas produced. Many people find that a sudden change in fibre intake can give them wind, but this is usually short lived and settles within a few days. However, those who are more sensitive should make gradual increases to their fibre intake, and persevere, as this will help to achieve a better balance of bacterial types and reduce the troublesome gas producers in favour of more helpful bacterial types.

Your gut bacteria produce short chain fatty acids – key ones being butyrate, acetate and propionate, each of which is used differently. Butyrate is used by the cells lining your colon and helps to reduce inflammation and protect against colon disorders. Acetate is absorbed and used by your brain, muscle and body tissues, and propionate is cleared by your liver and may help to lower your cholesterol and blood sugar levels.

Gut bacteria also play an important role in helping to boost your immune system by helping to kill harmful bacteria; stimulating infection-fighting cells in your bloodstream and by reducing the amount of harmful substances ‘leaking’ into your bloodstream.

Can my gut flora help to keep me healthy?
The simple answer is yes – look after your gut bacteria and you’re looking after your long-term health. Over the past 10 years, there has been a huge discovery of the amazing role that we now believe gut bacteria play in our health and wellbeing, mainly due to advances in technology that enable us to identify different bacteria and what they contribute. The gut flora is now being called the ‘forgotten organ’, and appears to influence a wide range of conditions including: obesity; diabetes; heart disease; irritable bowel syndrome and colorectal cancer. Interest is also growing into how the gut microbiome interacts with the central nervous system (called the gut-brain axis), and how this can affect mood and also conditions such as Alzheimer’s and depression. We don’t yet have the answers as to whether shifts in the gut flora cause disease or if these occur as a consequence, but research suggests that a diverse and stable gut flora can help to alleviate some of the symptoms and challenges that these conditions bring.

Does the menopause affect your gut flora?
Probably, but gut flora and the menopause is an area that hasn’t yet had a great deal of research. It may be more appropriate to ask whether the gut flora alters oestrogen levels, both before and during the menopause, as gut bacteria play a role in converting oestrogen to its active form, and lower levels of bacterial diversity have been linked to a fall in circulating oestrogens. More research is needed, but the gut flora could also play a role in the higher levels of abdominal fat and increased risk of cardiovascular disease that typically accompany the menopause.

How do I look after my gut flora?
Changes to your diet can result in rapid changes to your gut flora, so the good news is that you can quickly make a difference. Probiotic drinks and yoghurts provide a boost to the specific strain of bacteria that they contain, but only while you continue to take them. The route to developing a diverse gut flora, full of the more helpful types of bacteria appears to be eating a variety of foods that are rich in fibre every day and, ideally, topping up the food supply to your bacteria several times during a day. Fibre comes in all different types with some more easily fermented (e.g. soluble fibre in oats) and others more challenging (e.g. bran fibre from wheat). But there are bacteria specially adapted to use all types of fibre. The more types of fibre you regularly consume, the more diverse and stable your gut flora will be – a key to great health. What’s clear is that most of us eat far too few fibre-rich foods, with intakes of fibre hovering below 20g per day, way below the 30g a day recommended for good health. I recently read an article which concluded with the line: ‘We never really eat for just one – our trillions of little friends get fed with every bite’. So by choosing a balanced and nutritious diet with a good dose of fibre you’re helping to keep everyone happy!

Ghaisas S et al (2016) Gut microbiome in health and disease: linking the microbiome-gut-brain axis and environmental factors in the pathogenesis of systemic and neurodegenerative diseases. Pharmacol Ther. 158: 52–62
Flint HJ (2012) The impact of nutrition on the human microbiome. Nutrition Reviews 70: S10-S13
Manichanh C et al (2014) Anal gas evacuation and colonic microbiota in patients with flatulence: effect of diet. Gut 63: 401–408
Viera AT et al (2017) Influence of Oral and Gut Microbiota in the Health of Menopausal Women. Front Microbiol. 2017; 8: 1884
Makki K et al (2018) The Impact of Dietary Fiber on Gut Microbiota in Host Health and Disease. Cell Host & Microbe 23: 705-715

About the author
Angie Jefferson ( is a registered dietitian with a special interest in women’s health. She believes in helping women make small positive diet and lifestyle changes to deliver bigger health benefits.

Created Spring 2019

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