A healthy gut is fundamental to health and wellbeing. At its most basic, our digestive system is a tube through which food travels and from which nutrients and energy are taken into the body. But our gut also influences many other aspects of health, such as our immune system and even brain health, and many chronic diseases stem from the gut. Here we describe why the gut is fundamental to health, the role it plays in metabolic health and actions you can take to keep your gut healthy, such as eating more fermented foods.
The role of bacteria in the gut
Our digestive systems contain a huge number of bacteria, which together are known as the microbiome. The microbiome plays a key role in digestion, but researchers are now discovering how vital these microbes are to our overall health. Scientists estimate that each one of us has around 100 trillion micro-organisms living in our guts, weighing about two kilograms!
These microbes are our partners, they help us to get energy from food, and it is now understood that a healthy microbiome is fundamental to good health. The greater the diversity of the microbes the better - having a wider range of different bacteria appears to be beneficial to health. Low microbial diversity and dysbiosis (or imbalance), can lead to inflammation which has an impact on immune health, and may lead to a range of diseases, including:
inflammatory bowel disease
psoriatic arthritis
type 1 diabetes
asthma
atopic eczema
coeliac disease
obesity
type 2 diabetes
arterial stiffness
An imbalance of gut microbes due to diet or environmental factors can lead to an overgrowth of bad bacteria, the pathogenic organisms that cause chronic inflammation which can lead to the development of chronic metabolic and intestinal disease.
Figure 1. below summarises factors that can influence the health of the gut microbiome, along with the impact on our health when the microbiome is less diverse.
Figure 1. The role of gut microbiota in health and disease (Valdes, A. M. et al, 2018 BMJ)
The microbiome, obesity and diabetes
The gut microbiome seems to play a role in the development and progression of obesity. People who are overweight or obese are more likely to have an imbalance in the bacteria in the gut, with less diversity of microbes. The composition of the gut microbiome may influence the development of insulin resistance and Type 2 Diabetes. A number of factors can contribute to a lack of diversity, particularly diet, it is also known that other factors, such as the overuse of antibiotics disrupts a healthy microbiome, leading to obesity.
Fibre is considered very beneficial for gut health. Bacteria in the colon ferment fibre producing short-chain fatty acids (SCFAs), such as acetate, propionate and butyrate. These SCFAs are considered beneficial for metabolic health as they:
improve blood glucose control and insulin sensitivity
support appetite regulation and energy expenditure, and
improve the integrity of the gut barrier, by supporting mucous production, which is beneficial to immune health
Figure 2: Potential benefits of short-chain fatty acids for metabolic health (Blaak, EE et al 2020)
Increasing the diversity of microbes in the gut, particularly butyrate-producing microbes, is thought to be beneficial for people with insulin resistance and likely to reduce the risk of Type 2 Diabetes. A recently published cross-sectional study of 2166 participants found:
" higher microbiome diversity, along with more butyrate-producing gut bacteria, was associated with less type 2 diabetes and with lower insulin resistance among individuals without diabetes"
How to look after your gut
Here are some actions you can take to help you gut stay healthy or to improve its health:
1. Avoid highly processed foods
Highly processed foods, high in sugar, fat, and refined carbohydrates, have a harmful effect on our digestive health – they can cause inflammation and reduce the diversity and health of the microbes in the gut. A diet high in processed foods may lead to damage to the gut lining – causing leaky gut, which lets toxins and allergens enter the body and causes a weakening of the immune system.
The PREDICT study showed that diets high in very processed foods change the balance of microbes in the gut, increasing the number of ‘bad’ microbes. These ‘bad’ microbes are linked to poorer health, more inflammation, reduced blood glucose control and increased body weight.
2. Eat a wide range of fresh foods
Cook from scratch whenever you can, use fresh ingredients and minimise pre-packed foods, (particularly if there is a long list of ingredients on the packet, many of which you don’t recognise as foods!).
Try and eat a wide range of foods, as microbes love diversity! Include plenty of different fruit and vegetables, beans and pulses, nuts and seeds. Choose plenty of different coloured foods to maximise polyphenols, the substances which give colour to food, which are beneficial for the microbiome – i.e., green tea, olive oil, dark chocolate, berries.
3. Eat plenty of fibre
As detailed above, eating more fibre is a great way to improve gut health. Fibre comes from
plant foods and passes through the digestive system without breaking down or being digested. It is a prebiotic - providing food for the microbes in the colon, and a high fibre diet encourages a greater diversity of microbes, including the very beneficial butyrate-producing microbes.
It's easy to eat plenty of fibre if you're on a low-carb diet - good foods include nuts and seeds, fruit and vegetable as shown on the list here. Aim for 30g of fibre each day.
4. Try Fermented foods
Eating fermented foods is another great way to support your gut. Fermented foods contain probiotics - good bacteria that will improve your microbiome. A recent study by a team at Stanford University found that regularly eating fermented foods for just 10 weeks improves the health and diversity of gut bacteria. Given that lower diversity of gut bacteria is linked to greater risk of diseases such as obesity and diabetes, this is great news! The team also found that that eating fermented foods decreased inflammatory markers. Given that inflammation underpins many chronic diseases, this is also a very positive finding.
Fermented foods include live yoghurt, kefir, fermented vegetables such as sauerkraut or kimchi, kombucha – a fermented tea, certain cheeses, and even cider apple vinegar. If you’ve not eaten these foods in the past, go gently to start with, and increase your portion size gradually.
5. Plenty of fluids
Water plays an important role in digestion and in the absorption of nutrients from food, and not drinking enough can cause constipation. While water is good, you don’t have to just drink water - tea, coffee, herb teas will all provide the necessary fluid, but try and avoid sugary drinks.
6. Adopting regular patterns of eating, sleeping and exercise
We all benefit from routine around eating, sleeping and exercising and getting into regular patterns around all three will help your digestion. A random eating pattern can lead to problems such as heartburn, constipation, indigestion, ulcers, irritable bowel syndrome, leaky gut and body-wide inflammation. According to Dr Satchin Panda, eating in line with our internal body-clock helps to reduce the risk of digestive problems. Some simple tips:
Eating
- Eat meals at around the same time every day
- Avoid eating late in the evening or at night
- Try not to rush your meals, take time to eat and chew each mouthful well
- Eat proper meals, avoid snacking and grazing
- Try and eat within a defined eating window every day – say between 8am and 7pm, avoid all food outside those hours so that you give your digestive system a rest
Sleeping
- If possible try to get 8 hours sleep at night
- Go to bed and get up at the same time every day, even at weekends
Exercise
- Try and do some sort of exercise daily, even a short walk, as this promotes sleep
- Early morning and late afternoons are good times for exercise
7. Relaxing and reducing stress
Acute stress has a negative effect on digestion – it increases motility and fluid secretion causing pain, diarrhoea or interfering with normal bowel habits. Chronic stress may lead to more serious digestive problems, so it’s important to take action to take relax and look after yourself. Taking time out to enjoy yourself and your hobbies, taking exercise and spending time outdoors, and with friends and family will all help.
In conclusion
Looking after your gut is fundamental for your health now and in the future. By taking action to improve the diversity of your gut microbiome, you can reduce inflammation and your risk of a whole range of diseases. And don't forget - it's never too late to start as gut health can be improved by taking simple actions as described above.