There's nothing like the smell of fresh baked bread to get your mouth watering — but a lot of people these days find they cannot eat these delicious baked goods. The protein gluten found in breads and wheat products is often to blame.

People with the serious autoimmune disorder celiac disease have an extreme reaction to gluten. For others who say they react negatively to gluten, the reaction is less serious, but can still be disruptive and painful.

Laurie Allan of Toronto has what's become known as gluten sensitivity. "I have had digestive issues for a long time, like since I was in high school. But about six years ago, I was in a car accident and needed hip surgery. So I had a lot of chronic pain that came with that. And I read an article about how gluten may affect chronic pain. So if I cut that out, it might help. So I thought I'd give it a try. It didn't help with the pain, but what it did was really, really resolve my digestive issues, which was a complete surprise to me. So I thought, 'Hey! Maybe we're onto something.'"

It turns out there's a very good reason why people like Allan, who test negative for celiac disease, report feeling better after avoiding gluten. And it's not because they are sensitive to gluten. A new study published in the journal Gastroenterology suggests another culprit that travels along with gluten in wheat, rye, and barley — fructan — may be causing their digestive problems.

The case against gluten

Gluten-free French bread might have to be rebranded as low FODMAP bread to indicate it's also low in fructans, which may be the real culprit behind non-celiac gluten sensitivities. (Larry Crowe/Associated Press)

Scientists started suspecting gluten was not the cause of "gluten sensitivity" after a 2013 study also published in Gastroenterology by a team of scientists from Monash University in Melbourne, Australia.

They did a controlled, double-blinded randomized study where they got participants to eat identical meals that either lacked gluten or were full of it. In the lead-up to the study, all the participants had to follow a low FODMAP (Fermentable, Oligo-, Di-, Mono-saccharides And Polyols) diet.

"We knew that [FODMAPs] triggered symptoms," said Dr. Jane Muir, one of the study's authors and an associate professor of nutrition science and the head of the Department of Gastroenterology at Monash University. "So when we did this study with gluten in our patients, we made sure that we controlled their background level of FODMAPs going into the study."

FODMAPs are short-chained carbohydrates found in many foods, including wheat, barley, legumes, dairy products, and some fruits and vegetables. "So they're actually found widely in many foods and they're fine normally," says Dr. Muir. "But if you have too many of them, that can cause some gut discomfort. And that will happen in all of us if you have too many of them, but some people are particularly sensitive to them and this is where the problem is."

In their 2013 study, Dr. Muir and her colleagues made all the study participants follow a low FODMAP diet for two weeks before they challenged their participants with either gluten or a placebo. "To our surprise, [it] was completely random how they responded to the gluten. They actually responded more to placebo than the gluten. But what was happening in the two-week run-in period was their symptoms were really resolved with this low FODMAP diet. So they actually got a very nice level of control of their symptoms during that two-week run-in period."

To our surprise, [it] was completely random how they responded to the gluten. They actually responded more to placebo than the gluten. - Dr. Jane Muir, Monash University

That was their first clue that perhaps what was actually bothering those with "gluten sensitivity" wasn't gluten, but a FODMAP food.

The path to fructan​

The Monash University team went back to the lab and, to their surprise, they discovered that all the gluten-free products are very low in FODMAP. "So what we've decided was it looks like people are feeling possibly better on a gluten-free diet because they're actually reducing their FODMAP intake. It's not really to do with gluten at all. It might actually be these other carbohydrates that are triggering their symptoms. So that was kind of a lightbulb moment for us," Dr. Muir says.

Gluten-free croutons. (Cassidy)

There was one FODMAP in particular that stood out — fructan. Gluten and fructan tend to travel together in foods like wheat, rye, and barley.

"Fructans are polymers of fructose," says Dr. Muir. "And our body can't digest them, so we don't have the enzymes to digest them. And so they will pass into the large bowel where the bacteria really do like to ferment them. And in fermenting them, they produce gases. And that, of course, can distend the bowel and make people feel quite uncomfortable, bloated, it can cause wind, but can actually cause a lot of discomfort for some people."

The current study

Since gluten and fructan travel together in foods, scientists at the University of Oslo decided they wanted to take Dr. Muir's 2013 study a step further to tease apart the effects of gluten versus fructan.

Dr. Muir and her colleague from Monash University helped the Oslo team with their study design where they were going to challenge participants who do not have celiac disease, but self-report as gluten sensitive. The participants had to eat a muesli bar for seven days that either had gluten, fructan, or neither of them as a control.

It was the fructan , not the gluten, that triggered their symptoms. - Dr. Jane Muir, Monash University

"They did a very nice double-blinded crossover study in people who have self-reported non-celiac," says Dr. Muir. "It was the fructan, not the gluten, that triggered their symptoms. So that really confirms our earlier work and our suspicions that this is what was happening."

What to do if you think you are 'gluten sensitive'

Dr. Muir says for anyone who thinks they may have an issue, it's important to go to a doctor first to make sure they don't have celiac disease. If that comes back negative and the person reports still having issues with wheat products and feels better on a gluten-free diet, it might be worth looking into the low FODMAP diet with the help of a dietitian.

[The low FODMAP diet] really does need a dietitian to help explain and manage people through the program. There's a number of phases, if you like - this sort of a strict phase for just a few weeks, and then there's a reintroduction phase, and then there's sort of a maintenance phase. - Dr. Jane Muir, Monash University

"It really does need a dietitian to help explain and manage people through the program. There's a number of phases, if you like — this sort of a strict phase for just a few weeks, and then there's a reintroduction phase, and then there's sort of a maintenance phase."

Fructan might not be the only culprit

Dr. Muir says the low FODMAP diet only works on 70 to 75 per cent of patients with who report having gluten sensitivity. "It's obviously not working for everyone."

Dr. Elena Verdu, an associate professor at the Farncombe Institute at McMaster University, says there are other groups of proteins also found in wheat that could be triggering bowel issues, such as amylase trypsin inhibitors. "So it is not that fructans cannot be the cause of symptoms in patients with IBS. It's that there are many other components in different patients could cause symptoms."

Dr. Verdu says it's important to identify subgroups of patients that may react preferentially to one type of food restriction or another. Dr. Muir agrees: "We have to work to understand these other groups. Certainly there probably are other groups and there's probably a components of food that might be triggering these symptoms. And we need to do more research."

People who thought they had gluten sensitivity may actually be able to eat sourdough bread, which is low in FODMAPs. (Wikimedia Commons)

It just might turn out that people with "gluten sensitivities" may actually be able to bring some foods back into their diet, like sourdough bread that's low in FODMAPs — where they never thought they could before.