Trillions of bacteria live in our guts - and it's important to keep them happy, or you could find yourself not only with an upset tummy, but feeling ill in whole host of ways.
It is often assumed that bacteria is bad, leading to illness and disease. But, in fact, bacteria is essential for keeping us fit and healthy.
Bacteria and other microbes, such as fungi and viruses, live in our guts, playing a critical role in digestion, immune function and weight regulation - this makes the gut one of the most important parts of our bodies, says world expert gastroenterologist and University of Manchester academic Professor Peter Whorwell.
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By not treating our guts right, we can end up feeling under the weather unexpectedly.
The consultant gastroenterologist has shared his knowledge from years of treating patients and research, now operating the South Manchester Functional Bowel Service.
Every gut is different, says the doctor. You shouldn't panic if you're not uncomfortable, and find out what feels normal for you.
But there are some common signs to watch out for and plenty of ideas to suggest for people who want to stay well.
"The gut is the centre of your health," he says.
"If it's working normally, you're more likely to be healthy."
An unhappy gut is like a blocked drain, says the Professor, and it desperately needs unplugging. That's why bloating and constipation could occur in people suffering from gut difficulties.
On the other end of the spectrum, people struggling with their gut might not be able to stop their bowel movements.
Bloating which gets worse as the day goes on can be a sign of irritable bowel syndrome.
However sometimes, frequency isn't as much of an issue, says Professor Whorwell. Whether your bowel movements are uncomfortable - and what comes out of them - is more important.
Extremely dark, or clay coloured, poos on a consistent basis can be a sign that your tummy needs looking at by a doctor, he says.
Some undigested food, such as sweetcorn, also isn't a problem. But 'if there's this morning's meal in there', you should be asking questions.
Some pass it, some don't. When it's particularly smelly, however, it's 'worth looking at what you're eating', says the doctor.
Certain vegetables including sprouts and cabbage come with side orders of sulphur, leading to smellier wind and more troubled tummies.
Insomnia or simply poor sleep may be caused by an unhealthy gut.
This in turn can lead to chronic fatigue.
Most of the body's serotonin - the hormone that affects mood and sleep - is actually produced in the gut.
This means that damage and imbalance can impact your ability get adequate rest and even result in mood swings or changes.
If you gain or lose weight unintentionally, without making changes to your diet or activity levels, this may be a sign of an unhealthy gut.
An imbalanced gut can impair your body's ability to absorb nutrients, regulate blood sugars and even store fat.
This can lead to insulin resistance or the urge to overeat due to the lack of nutrients absorbed by the body - resulting in weight gain.
On the other hand, an unhealthy gut may result in weight loss caused by small intestinal bacterial overgrowth (SIBO).
Many patients who come to Professor Whorwell's clinics complain that their skin and hair isn't as good, he says. This symptom can, too, be put down to a bacteria imbalance.
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"Probiotics are a really good idea," says Professor Whorwell.
"We live such clean lives so the bacteria isn't always as strong in our gut as it once might have been.
"If you've been taking antibiotics, which wipe out all the bacteria in your body, it can be particularly good to have a probiotic to rebalance your system."
Often, probiotics come in yoghurts, but those with sensitivities to dairy can find probiotics in tablet form at health food shops, he adds.
If you're struggling with bowel movements, a laxative from a pharmacy - taken in the appropriate dose - can be a useful solution, says the gastro expert.
He wants to reassure people who may be reluctant to take laxatives to make use of the medication, adding that 'they will not make your bowel more lazy', debunking a common myth.
"You're not going to be feeling great if you're backed up. Unblock that drain," says Professor Whorwell.
Equally, if you've been suffering from an acute vomiting or diarrhoea bug, rehydration sachets like Dioralyte are a good option, according to Professor Whorwell.
If you're concerned that you may have sensitivities to a certain ingredient such as gluten or lactose, it's always worth trying to take that out of your diet for a couple of months, says Professor Whorwell.
"It's not going to do you any harm," he told the Manchester Evening News.
"Just don't take out more than one thing at once, otherwise you won't know what's worked and what hasn't."
Another common misconception is that more fibre, fruits and vegetables are the answer to all gut problems. In fact, high doses of fibre can make complaints like irritable bowel syndrome worse.
Again, says the professor, this might not work for every gut and you should monitor how your diet affects you personally.
If you're finding fibre makes your tummy grumble, for example, switch to something lighter like Rice Krispies for a period, he suggests.
If your problems are persisting over time - for example, if you have acute vomiting or diarrhoea for more than a few weeks - you should seek professional help, says Professor Whorwell.
But if you have been suffering with chronic tummy trouble, there are plenty of benefits to seeking help from a doctor, including getting a tailored diet plan or medication to suit your specific needs.
Do not ignore any bleeding, get checked out by your GP, he adds.
“As a general rule of thumb, it’s acceptable to open your bowels three times a day before it’s diarrhoea, and three times a week before its constipation. That’s the by-the-book definition," says the Professor.
“But if someone who was opening their bowels twice a week and wasn’t uncomfortable, I wouldn’t do anything about it. If someone goes once a day but can't get to the toilet fast enough, and it comes out in a torrent, that looks like trouble.
“If your bowel function is causing you problems, you should think about doing something about it. If not, leave it be. Everybody is different.”
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