It can be tricky to diagnose IBS due to its varying symptoms and unpredictability. According to NICE guidance with the use of the Rome III criteria, IBS should be considered if there is abdominal pain/discomfort associated with bowel movements and/or a change in bowel habit involving two or more of the following symptoms:[5,6,8-10]

1. Altered stool passage (straining, urgency, incomplete evacuation)

2. Abdominal bloating (more common in women than men), distension, tension or hardness

3. Symptoms made worse by eating

4. Passage of mucus

Other symptoms that can occur include fatigue, bladder symptoms, nausea and backache.[6]

IBS symptoms can be like those of inflammatory gut diseases such as Crohn’s disease or ulcerative colitis, so it is important to rule out such conditions first. For example, a faecal calprotectin level to show inflammation in the gut, and a blood test for IgA tissue transglutaminase antibody (tTGA) and total IgA to rule out coeliac disease.[6,10,11] Other blood tests usually done as a screening for bowel disorders include full blood count to check for anaemia and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to check for infection and inflammation.[6,10] Food allergy tests should not be used to evaluate food intolerances in IBS patients.[5]

Any red flag symptoms alongside abdominal symptoms such as gastrointestinal bleeding, severe watery diarrhoea, fever and/or weight loss should be investigated urgently. Once these other conditions have been ruled out, the diagnosis of IBS is made.[6] Invasive tests such as ultrasound, sigmoidoscopy, colonoscopy or endoscopy are not necessary to confirm IBS and are only required to investigate other GI diseases with red flag symptoms. [6,10]

IBS is not caused by diet; however, certain foods can affect the symptoms. Reported common IBS trigger foods include: [5,12]

• Legumes such as beans, lentils, chickpeas

• Brassicas such as cabbage and kale

• Onions

• Sugars such as fructose and lactose

• Wheat and/or gluten

• Barley

• Oats

• Nuts, seeds and popcorn

• High-fat foods

• Caffeine

• Alcohol

• Spicy foods

• Raw fruits and vegetables

• Prunes          

• Artificial sweeteners such as sorbitol, mannitol, xylitol, maltitol and erythritol

According to the IBS dietary algorithm, if this first-line advice is not helping remission of symptoms, then second-line advice should be trialled.[7] This includes food avoidance and food exclusion diets, eg, elimination diet, low-FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet.[6,7,13] These treatments should only be provided by a ‘healthcare professional with expertise in dietary management’, which ideally would be a registered dietitian or nutritionist with the appropriate experience. [5,6]

Other dietary treatments that have limited evidence include:[2,16]

• ·         Magnesium

• ·         Herbal Teas, peppermint and green tea

• ·          Peppermint oil -this has been established as a safe and effective option for IBS relief

Healthcare professionals should discourage the use of aloe vera in the treatment of IBS, as there is very little evidence for its efficacy.[6]

THE LOW-FODMAP DIET
This is a short-term ‘diagnostic’ diet to identify food triggers. The aim is to reduce foods high in fermentable oligosaccharides, disaccharides, monosaccharides and polyols, such as apples, cherries, plums, garlic, leeks and onions, grains and cereals, legumes and beans and dairy products, etc. [13]
Points to consider:

• This diet requires three- to six-week restriction of all FODMAP foods. Then, if GI symptoms improve, each food group is reintroduced one at a time over the next few weeks to help identify which foods are triggers.

• It has been shown to reduce IBS symptoms in 75% of people with IBS [13]

• It’s an individualised approach.

• The diet is not recommended to be followed in the long term, but rather to help those with IBS identify what high-FODMAP foods they need to avoid [7]

THE ELIMINATION DIET
Elimination diets are short-term diagnostic diets used to identify foods to which you may be sensitive or intolerant, such as lentils, eggs or gluten. The point of an elimination diet is to avoid a certain food for around one month to see if symptoms improve, then reintroduce to see if symptoms occur again.[14]
Points to consider:

• If it is not strictly adhered to, it will not be definitive and should only be followed under the guidance of a dietitian to ensure that there are sources of nutrients and vitamins. [14]

• Neither the elimination nor low-FODMAP diets are advisable for those with a low BMI, ongoing weight loss or nutritional deficiencies. [5]

THE GLUTEN-FREE DIET
This involves avoiding gluten-containing foods such as wheat, barley and rye, such as bread, pasta, cereals, crackers, cakes and biscuits. [5]
Points to consider:

• There is not much evidence for gluten restriction for IBS management, but it has been reported that 20% of IBS patients found relief from symptoms with a gluten-free diet [5]

• Wheat is a high-FODMAP food, so it could be argued that the benefits of a gluten-free diet in IBS are due to the lower FODMAP content rather than gluten specifically. [5]

THE LOW-HISTAMINE DIET
Histamines are found in preserved and fermented foods such as some canned foods, cheese and alcohol [5]
Points to consider:

• There are health conditions linked to elevated histamine levels, such as mastocytosis, where mast cells accumulate and cause organ damage.[15] However, it is not clear of its relevance in IBS. [5]

  
  

There are many pharmaceutical options for IBS depending on symptoms and severity. Antispasmodic agents, such as hyoscine bromide, can be used for people with IBS to treat bloating and abdominal pain symptoms.[6] Laxatives should be considered for the treatment of constipation in people with IBS-C. However, lactulose should be avoided due to the risk of lactose intolerance and the potential to worsen symptoms of bloating.[6,11]

Some laxatives are safer than others for long-term treatment of constipation.[21] Some can be habit-forming, eg, stimulant laxatives that can be harmful if used regularly.[21] Clinicians should recommend laxatives based on IBS-C symptoms and clinical history.

Newer laxatives, such as linaclotide or lubiprostone, are now recommended for people with IBS-C only if previous laxatives from different classes have not helped and constipation has been present for at least 12 months.[6] Loperamide is the first-choice antimotility agent for diarrhoea in people with IBS-D.[6]

Tricyclic antidepressants (TCA) are a second‑line treatment option for people with severe IBS, and serotonin reuptake inhibitors (SSRIs) can be trialled if TCAs are not effective. The doses used are normally lower than the doses used to treat depression.[11] Other medications that can be prescribed are Mebeverine and Alverine, which can help reduce bowel spasms and abdominal pain.[11]

ALTERNATIVE TREATMENTS

There are many more options now for those who suffer from IBS to try alternative treatments that do not involve diet or medications and focuses on psychological wellbeing.[4,22]  Now there is evidence to show that reducing stress can help symptoms due to the gut-brain connection and the known effect of stress on gut function.[4,23] Central processing mechanisms in the brain exacerbate gut regulation by causing visceral sensitivity and central processing defects.[4,24] These defects lead to the development and flare-ups of the disorder.[4] Stress management strategies include:[12]

• Walking

• Meditation

• Reading

• Massage

• Tai chi

• Yoga

• Journaling

Psychological interventions are now considered significant and effective treatments for chronic disease management. [4] CBT and hypnotherapy have been shown to improve IBS symptoms, and these treatments are becoming widely available on the NHS, although access is still an issue in some regions. [4,5,12,14,23]