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SOUTH Beach, paleo, vegan, juice cleanse鈥� and FODMAPs. Short for fermentable oligosaccharides, disaccharides, monosaccharides and polyols, the name FODMAPs certainly doesn鈥檛 have instant appeal, but a diet focused on avoiding these substances is catching on with the public and the medical profession alike. The low-FODMAP diet is based not on celebrities鈥� waistlines or detox bunkum, but on the premise that a healthy gut leads to a happy life. So popular is it proving that there are now claims the diet could alleviate everything from indigestion to chronic fatigue.

Over the past few years, we have become much more clued up about the extensive influence of the gut in health and disease, and the impact our lifestyle choices can have on what some researchers like to call our 鈥渟econd brain鈥�. Gluten, a protein found in grains such as wheat, barley and rye, has taken much of the blame, with a growing number of people claiming that they have some sort of gluten intolerance. Global sales of gluten-free food , and specialist supermarket aisles now heave with gluten-free products, even though the idea that people can be gluten-sensitive even if they don鈥檛 have the autoimmune disorder coeliac disease has been largely debunked.

Now the gut health tide is turning once again, and it appears that gut problems linked to certain foods like bread might be real for many. What鈥檚 more, the secret to dealing with these problems could fly in the face of established healthy eating advice.

The most common cause of gut problems is irritable bowel syndrome (IBS), a catch-all term for a poorly understood constellation of symptoms including bloating, diarrhoea and constipation. It affects millions, although it doesn鈥檛 appear to be on the rise, with the incidence in the West put at between 5 and 15 per cent of the population. If, however, it feels like you can鈥檛 go to a dinner party without someone talking about their gut problems, that might be down to a shift in awareness. 鈥淧eople are noticing symptoms more and reporting them,鈥� says Peter Gibson at Monash University in Melbourne. 鈥淪ixty years ago we had no criteria to diagnose IBS, and people with gut symptoms just put up with it.鈥�

鈥淭oo much fibre, fruit and veg could be causing a rise in gut complaints鈥�

IBS symptoms overlap with those of coeliac disease. For coeliacs, consuming gluten causes symptoms such as diarrhoea, constipation, cramps and fatigue, and triggers a faulty immune reaction which damages the lining of the gut. Although unrelated to IBS in origin, coeliac disease has been attracting attention because it is proving to be , affecting 1 per cent of people. However, many who test negative for it 鈥� showing no signs of making antibodies in response to gluten, or of gut damage 鈥� still complain that wheat products make them feel unwell. This has been labelled non-coeliac gluten sensitivity, although the condition remains controversial.

Some argue that gluten is poorly digested by many people, and that its ubiquity in modern, processed food is at odds with the diet that the human gut evolved to deal with. 鈥淲heat is a friend that has outstayed its welcome for some of us,鈥� says David Sanders at the University of Sheffield, UK. over whether gluten can cause symptoms in non-coeliacs has been fuelled by the fact that cutting it out has become a fashionable lifestyle choice. Studies show that many non-coeliacs are choosing to avoid gluten because they believe doing so is healthy, despite .

In one study of 22,000 adults in the US, the proportion eating a gluten-free diet more than , although the proportion who had coeliac disease stayed roughly constant. Also in 2013, 30 per cent of adults in the US reported .

鈥淭he gluten-free craze is a marketeer鈥檚 dream and the perfect worried-well scenario,鈥� says Kevin Whelan at King鈥檚 College London. 鈥淲e are seeing people avoiding it in the belief this will help them lose weight or improve their overall health. But beyond coeliac disease, gluten鈥檚 role in optimising health is nowhere near what people think it is.鈥�

Even if gluten is not itself the culprit, we are now understanding why so many people believe they are sensitive to it. A growing body of evidence over the past few years points the finger at FODMAPs. These carbohydrates are present in numerous foods, including wheat, which contains some called fructans. 鈥淚f you go on a gluten-free diet you reduce probably 50 per cent of your FODMAPs,鈥� says Gibson. Rather than having some sort of sensitivity to gluten, it seems that for some people with IBS, FODMAPs could be the trigger.

That was illustrated by a recent trial in which 59 non-coeliac adults on gluten-free diets were fed identical-tasting cereal bars packed with either gluten, fructans or neither. Those who had the fructan bar compared with the control group, whereas those who had the gluten bar felt no worse afterwards. 鈥淟ike many studies, that showed the fructans were the signals. If gluten is a cause of IBS, it鈥檚 nowhere near as frequent as people say,鈥� says Gibson, a pioneer of research in this area.

As well as being present in wheat and grains, FODMAPs are found in fruits and vegetables such as onions, garlic, apples and chickpeas. MRI studies show that when digested, these compounds , causing distension. That doesn鈥檛 cause an issue for most people, but for up to 70 per cent of people with IBS, reducing intake of these foods provides .

The low-FODMAP diet is considered so effective for IBS that it is now recommended by the National 午夜福利1000集合 Service in the UK and bodies including the Gastroenterological Society of Australia.

The type and quantity of FODMAPs that trigger symptoms varies enormously between individuals, but Gibson says the worst offenders are those in onions, garlic, wheat, rye and barley. This variability means anyone embarking on a low-FODMAP diet should seek the help of a trained professional rather than relying on internet articles, although health authorities are still struggling to train enough people to meet the demand, Gibson says.

Not for good health

As the buzz around the low-FODMAP diet spreads, it is attracting attention for its potential in other gastrointestinal conditions, including acid reflux and indigestion. The diet is now being of inflammatory bowel diseases (IBDs) such as Crohn鈥檚 鈥� conditions that are becoming more frequent in the West, possibly because of smoking and additives in the food we eat. 鈥淚BS-like symptoms are very common in people with IBD,鈥� says Gibson. 鈥淵ou wouldn鈥檛 put them on a low-FODMAP diet if they鈥檝e got very active inflammation, but if it鈥檚 well controlled it is very effective.鈥�

After researchers noticed that people with IBS felt more tired when they ate lots of FODMAPs and less so on a low-FODMAP diet, there has been hope it might help people with , who also have a high incidence of IBS. But Gibson says the evidence so far is weak and the diet鈥檚 effect on fatigue only happens among people with IBS.

Although it is appealing to think that we might all benefit from fewer FODMAPs in our life, 鈥渋f you don鈥檛 have bowel problems there is absolutely no rationale for being on a low-FODMAP diet鈥�, says Gibson. 鈥淭his is not a diet for good health.鈥� One drawback to the diet is that it cuts out foods that are important sources of vitamins, fibre and nutrients such as calcium. Recently, there have also been concerns that it in the gut, and the long-term consequences of the diet remain unclear.

Many people trying to avoid FODMAPs struggle to work out which foods to eliminate. 鈥淚t has helped an awful lot of people,鈥� says Peter Whorwell, a gastroenterologist at the University of Manchester, UK. 鈥淏ut for one patient it will be tomatoes, the other lettuce, the other none of the above.鈥�

Intriguingly, a third of people with IBS who try the diet reap no benefits at all. For them, some researchers are now looking at a more controversial alternative.

When it comes to gut health, one of the most common pieces of advice has been to eat plenty of fibre, such as wholegrain bread and fibrous vegetables, which help keep the gut working properly and can also reduce the risk of cancer and cardiovascular disease. But it now seems that . Some types of fibre release gas when fermented in the bowel, causing irritation in sensitive individuals.

Whorwell was one of the first to demonstrate that reducing fibre could be beneficial in IBS, with a study finding that wheat bran made 55 per cent of people with IBS feel worse and only . The idea has been gaining ground, although it has lately been overshadowed by the fuss over FODMAPs. Whorwell often advises his patients to try switching from wholegrain to white bread. 鈥淔ibre is just as important as FODMAPs in aggravating irritable bowel,鈥� he says.

Whorwell even speculates that a push for healthier diets 鈥� high in fibre and fruit and vegetables 鈥� may be contributing to a rise in gut complaints. 鈥淭hirty years ago, nobody had heard of five a day,鈥� he says. 鈥淚t amazes me how many vegetables people are eating these days.鈥�

The trouble is that advising patients to eliminate both FODMAPs and fibre flies in the face of good nutrition. In future, IBS treatment will probably involve supplements containing targeted combinations of beneficial, slow-fermented fibres, says Whelan, who is studying fibre鈥檚 effects on the gut.

And although gastroenterologists remain divided over the issue of gluten, some believe it may yet prove to have adverse effects beyond coeliac disease. 鈥淭he research evidence is nowhere near catching up with the marketing machine,鈥� says Whelan. 鈥淏ut I think non-coeliac gluten sensitivity exists. Some people, when given a gluten challenge, do get symptoms, though identifying who they are and how they differ from people actually responding to fructans is difficult.鈥�

The good news for those with gut problems is that the diversity of symptoms and causes are being investigated like never before. For those who don鈥檛, however, it might be time to step off the bandwagon, says Sanders. 鈥淚f you don鈥檛 have any symptoms, you don鈥檛 need to be on any of these diets.鈥�

This article appeared in print under the headline 鈥淲hat鈥檚 up with your gut?鈥�