Probiotics help top up the friendly bacteria living in our guts, with potential benefits to our overall health – by Alice Ball.

Bacteria has long had a bad reputation.

We take antibiotics to kill bacterial infections, clean surfaces with antibacterial solutions, and these days are encouraged to regularly slather our hands in antibacterial gel.

So the thought of actively choosing to put bacteria into our bodies might seem, quite literally, hard to swallow.

Our guts, however, are home to an estimated 1,000 species of bacteria, each with a different function.

They help to keep pathogens in check, aid digestion and absorption of nutrients, and contribute to healthy immune function.

For our bodies to be happy and healthy, we want to make sure that these gut bugs are flourishing – but in a healthy balance.

This is where probiotics come in.

Probiotics are ‘good’ bacteria found in fermented foods, drinks or in supplement form, and which may support balance in the gut.

Even faecal transplants (FMT), which are used to combat Clostridioides difficile (C. diff) infection, could be considered a form of probiotic treatment, as stools with beneficial bacteria are taken from healthy hosts and transplanted to the patient.

Notably, C. diff infections can occur after antibiotics prescribed for other infections kill off beneficial bacteria, leading to severe diarrhoea and abdominal pain.

In 2020, the first licensed stool bank in England, which supplies FMT treatment to patients in the NHS, reported in 78% of cases treated with FMT the patient’s diarrhoea had stopped and not returned in the 90 days after treatment.

Why probiotics are good for you

There are many different strains of probiotics, and health benefits can vary.

For example, in a systematic review of 20 randomised control trials that looked at the effects of Lactobacillus and Bifidobacterium probiotic strains on the duration of colds in otherwise healthy children and adults, participants who received a probiotic recovered a day sooner than those who were given a placebo.

Research has also associated certain beneficial bacteria with a reduced risk of cancer.

One study found that men who consumed two or more servings of live yoghurt per week, for example, were 19% less likely to develop an adenoma (a pre-cancerous growth).

For adenomas that were likely to become cancerous, the lower risk was even greater at 26%.

In 2020, researchers from Lancaster University also suggested that one of the causes of breast cancer may be inflammation triggered by harmful bacteria, and that consuming natural yoghurt containing bacteria may inhibit inflammation.

This is because the bacteria found in live yoghurt — Lactobacillus — is similar to the bacteria found in breastfeeding mothers, whose risk of breast cancer is reduced by 4.3% each year.

When it comes to digestive health, probiotic strains may also help to relieve symptoms of mild to moderate ulcerative colitis (IBD) as well as bloating and gas in irritable bowel syndrome (IBS).

However, caution is recommended when adding fibre in with IBD.

Positive associations between eating probiotic foods and better health outcomes may also be due to a healthy lifestyle, overall.

Probiotics and mental health

Diverse gut bacteria have also been positively linked to mental health.

Dubbed ‘psychobiotics’ it is thought that these types of probiotics may positively impact mental health by altering the way the gut communicates with the brain.

Although a recent review of available evidence concluded that it is not clear whether probiotics can help with anxiety, it reported that taking probiotics with or without prebiotics may help to ease depression.

A recent study also found that probiotics may assist weight loss.

A study on 100 children with obesity found that those who were given probiotics Bifidobacterium breve BR03 and Bifidobacterium breve B632, in addition to following a calorie-controlled diet, lost more weight and had improved insulin sensitivity compared with children who only followed the diet.

Can probiotics cause gas?

Despite this apparent evidence to support use of probiotics, however, their effects may not always be desirable.

In some circumstances, over consuming probiotics in supplement form may result in the accumulation of bacteria in the small intestine — called small intestine bacterial overgrowth (SIBO) — causing brain fog and severe bloating.

In one study of 30 patients, 22 who reported problems like confusion and difficulty concentrating, in addition to gas and bloating, were all taking probiotic supplements.

When researchers looked further, they found large colonies of bacteria breeding in the patients’ small intestines, and high levels of D-lactic acid being produced by the bacteria’s fermentation of sugars in their food.

The authors did however note that these problems were associated with probiotics in supplement form rather than from food sources, which are generally considered safe because of the smaller amounts of bacteria present.

Another caution against supplementing with probiotics is that the gut needs a variety of bacteria and that one type may not be appropriate in all cases.

A 2017 review suggested that children and adults with severe illnesses or compromised immune systems should avoid using probiotics, or speak to their doctor before taking them.

A registered nutritional therapist will also be able to advise on their use.

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