Has Gluten-Free Failed You? Here’s What To Do Next

Emeran Mayer MD, PhD
10 min readDec 13, 2017

If you’ve had virtually any health issue in the last decade, you may have considered or actually tried going gluten-free. Indeed, many people swear that cutting gluten out of their diets has been their best health move.

Unfortunately, going gluten-free does not work for everyone. This is true even for some with celiac disease for whom a gluten-free diet is still the only medically-accepted therapy. A recent study among children with possible celiac disease found that only half enjoyed complete clinical improvement on a gluten-free diet. Another study showed that only 8% of people with celiac disease who followed a gluten-free diet had normal-looking intestinal biopsies — almost a third showed no improvement or actual worsening.

But as more people without celiac disease (so called non-celiac gluten sensitivity, NCGS) experiment with going gluten-free for other ailments, it’s not surprising that we’re seeing more instances of the gluten-free promise failing its mission.

If this is true for you it’s worth asking, “What do I do now?”. The great news is that there’s plenty.

Where the gluten story confuses us all

There is a notable surge of people who don’t have celiac disease or wheat allergies who go gluten-free anyway. Recent data pegs this number at 6% of the US population. That’s a whopping six times the number of people diagnosed with celiac disease.

This phenomenon is so substantial that doctors struggle to come up with ways to describe it. Some long-winded terms include non-celiac gluten sensitivity (NCGS), non-celiac wheat sensitivity (NCWS) or people without celiac avoiding gluten (PWAG).

As surprising as their numbers are, the results some people experience are even more eye-opening. Even though they have no obvious reason to benefit from avoiding gluten, some without celiac disease report feeling better on a gluten-free diet.

On the flip side, among those with every obvious reason to benefit from avoiding gluten (meaning, those with celiac disease), some experience limited benefit from going gluten-free.

So what gives?

There are several possible explanations. But one that seems most likely is this — Clearly gluten isn’t the entire story.

Things make better sense if we remember that gluten is just one nutrient found in foods like wheat, barley and rye. When someone avoids gluten-containing foods, they also avoid other food components besides gluten, including other nutrients and particularly additives.

For people who don’t have celiac disease but notice they feel better when they go gluten-free, it’s possible that they’ve eliminated a component other than gluten that was the real culprit. In other words, something other than gluten may have been the cause of their symptoms all along.

On the other hand, for people with celiac disease who don’t notice relief when they go gluten-free, it’s possible that they’re reacting badly to a component that hasn’t been eliminated on a gluten-free diet. In other words, something other than gluten may have been aggravating their symptoms.

Both scenarios suggest the same conclusionsomething besides gluten is involved.

That other component may in itself be the actual problem or it may be a co-conspirator with gluten to make susceptible people feel worse.

If not gluten, then what?

The clear front-runners in the race to de-throne gluten as the next “it” component are not a single nutrient like gluten — they’re a group of specific sugars with complex names.

Their debut came in a 2014 study published by Australian researchers at Monash University. This study looked at how people with irritable bowel syndrome (IBS) felt when eating a standard western diet for three weeks compared to three weeks on a diet without these specific sugars.

The results showed that people with IBS had significantly less digestive symptoms while on the diet without these sugars. The researchers concluded that people with IBS should consider avoiding these sugars as first-line therapy. Many doctors and people with IBS agreed, putting these sugars on our radar.

More recently, these specific sugars surfaced again in a Norwegian study. This study tried to determine if gluten is the actual reason non-celiacs who avoid gluten feel better. To answer this question, they recruited a group of non-celiacs who feel better gluten-free. In separate weeks, the researchers fed them unmarked muesli bars filled with either gluten, fructan (one of the specific sugars) or neutral bars without either. Along the way, participants were asked to rate their digestive symptoms.

Surprisingly, the non-celiac gluten avoiders didn’t notice much difference during the week they ate gluten bars compared with the week they ate neutral bars. Even more surprising, they felt significantly worse during the week they ate bars filled with fructan.

This unexpected finding has experts wondering if some people experience a big placebo effect on a gluten-free diet by decreasing their food-related anxiety.

It also underscores a bigger question — was gluten the wrong culprit all along?

The post-gluten era: Specific sugars in detail

Studies like these have many lauding these specific sugars as the next gluten. But these sugars come with their own challenges. First, unlike lonely gluten, there are many of them. But like gluten, eliminating them can be challenging because they’re found in a lot of foods we commonly eat. Finally (a personal pet peeve), some of them are associated with really long and confusing names, which we’ll try to simplify for you here.

There are two types of specific sugars to know about. The first are clustered under the acronym “FODMAPs”. This stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols, which is a mouthful. You may have already heard of them.

The second is a lesser-mentioned but very common sugar that can also cause significant problems called sucrose. We suspect you’ll hear more about this in the near future.

Why these specific sugars? Many are what we call prebiotics. Prebiotics are food components which can’t be broken down by our own enzymes. As a result, they end up in the colon where they become food for gut microbes. These microbes ferment these sugars into components we can absorb. However, this process produces gas which can cause bloating and discomfort, especially in susceptible people.

Here they are, one-by-one:

Oligos — Fructans and GOS

Remember the Norwegian study earlier? In that study, the muesli bars that actually caused more discomfort than gluten contained fructans, which is a type of oligosaccharide (or oligo for short). The other type of oligo is called galacto-oligosaccharides, or GOS. Oligos are the “O” in FODMAPs.

Oligos are found in foods we usually associate with as dietary fiber, like onions, prunes, beans and wheat. Oligos are used as prebiotics and have been shown to increase the abundance of certain microbes, such as Bifidobacteria.


Lactose is a disaccharide, giving us the “D” in FODMAPs. Most of us know lactose as the sugar famously found in dairy products like milk, cheese and ice cream.

People with lactose intolerance don’t have enough lactase, the enzyme that helps us digest lactose. For them, eating too much dairy can trigger gas, pain and diarrhea.

Lactase deficiency is actually the default for adult humans with the exception of Inuits and some Scandinavians. The majority of us are programmed to produce lactase only in the first few years of life when we’re reliant on breast milk. If you still want to drink lots of milk as an adult, consuming low lactose dairy products is the way to go.


Fructose (not to be confused with fructans discussed earlier) is commonly known as fruit sugar. Chemically, it’s a monosaccharide, giving us the “M” in FODMAPs.

No surprise, you’ll find fructose in many fruits like apples and pears. You’ll also find fructose in some vegetables like asparagus, as well as in sweeteners like high fructose corn syrup.

“Some people who are fructose intolerant run into trouble when their diet includes foods that contain more fructose than glucose. This is because glucose helps your intestine absorb fructose. When fructose outnumbers glucose, the extra fructose remains in our gut as ferment fodder. Additionally, the extra fructose pulls water into the small intestine, leading to a cascade of digestive symptoms.”

Kate Scarlata, RDN, global FODMAP expert and New York Times Best Selling author

Keep in mind that the biggest culprit is the excess industrial grade fructose that has been added to many foods in the North American diet — not the fructose from fruit where it’s combined with other plant components, mainly fiber.


The “P” in FODMAPs refers to polyols. One way to spot a polyol is that they often end in “-ol”, like sorbitol and mannitol. They’re found in vegetables like cauliflower and mushrooms, fruits like apples and peaches, and as sugar substitutes like xylitol.

Because they’re generally not well absorbed and can pull water into our intestines, eating too much of them can cause discomfort and diarrhea.


Finally, separate from the FODMAPs is another sugar worth paying attention to called sucrose. It’s technically not one of the FODMAPs, but you can remember it as the “s” if that helps.

Most of us know sucrose as “table sugar” or “white sugar.” It’s the sugar we use to sweeten things. Sucrose also occurs naturally in things like fruits and juices.

Sucrose is important to know because some people who don’t respond well to a gluten-free or low FODMAPs diet may be eliminating the wrong sugars. In other words, they may actually be having trouble with sucrose instead. This is particularly true for people who have a condition known as genetic sucrase-isomaltase deficiency (GSID), also called congenital sucrase-isomaltase deficiency (CSID).

Like people who are lactose intolerant, people with GSID don’t have enough of an enzyme called sucrase which helps digest sucrose. Even more, they also lack isomaltase, another enzyme that helps digest maltose, a sugar found in many starches including wheat. In these susceptible people, eating too much of the wrong food can trigger many of the same symptoms seen with intolerance to gluten and FODMAPs.

So how do you know which is the problem sugar for you?

The nice thing about going gluten-free is that you only have one nutrient to focus on. In stark contrast, the sheer number of these specific sugars feels very intimidating for those planning to avoid them. How can you know which ones are the true culprits, if any?

Just as with a gluten-free diet, the best approach to finding your answer is to do some diet detective work. First, find a skillful dietitian to help guide you responsibly and safely. Then keep a detailed journal of what you’re eating and how it makes you feel. This food-symptom journal will help you and your dietitian spot any interesting trends or associations between certain foods and symptom flares.

The role of elimination diets

If you’re still stumped after reviewing your food-symptom journal, the next step may be to try a carefully-devised elimination strategy with your dietitian. The goal of an elimination diet is to figure out if a particular food or nutrient is causing you problems. A gluten-free diet is a classic example of an elimination diet.

In general, you start by removing certain foods from your diet for a period of time and observe if this change makes any impact in how you feel. Food-symptom journals are super helpful in keeping track of how things are going. Based on what you notice, your dietitian may suggest various next steps. These may include removing more foods from your diet, adding back some foods or even changing the foods you eliminate altogether.

Because there are many sugars to consider, you’ll probably have to adjust the foods in your elimination strategy several times. This is when the expertise of your dietitian comes in handy. These refinements help you narrow down the suspects more specifically. Hopefully, this also leads you to a shorter list of restricted foods. Like the non-celiacs in the Norwegian study, you may find that you’re perfectly OK to eat some foods you had been avoiding.

Ultimately, elimination diets give you clarity on foods that are the true culprits making you unwell. This will give you an improved sense of understanding and control over how you feel, and possibly even wider food choices.

Work with a team for greater success

First, adopting any diet can affect your health, so make sure you work closely with your doctor and dietitian.

“Navigating this larger group of specific sugars is a bit trickier than gluten. For instance, unnecessarily avoiding these sugars can deprive your gut microbes of beneficial prebiotics and cause unintended problems. It helps to have an expert to guide you on how to do it safely and in the least uncomfortable way.”

Nancee Jaffe, MS, RDN, registered dietitian, UCLA Vatche and Tamar Manoukian Division of Digestive Diseases

Also, there are many great resources you can add to your team that make the process easier. Free tools like Selectivor have pre-set diet templates, including templates for diets that are free of gluten and each of these sugars. This allows you to know which foods to avoid depending on what you’re eliminating and to easily work with your dietitians and doctors.

For helpful information on FODMAPs, check out the Monash University site, their FODMAP app and Kate Scarlata’s blog.

If you’re interested in learning more about GSID and sucrose intolerance, extensive information can be found at www.sucroseintolerance.com and IFFGD.

Wishing you success

Many of you took on the rigors of a gluten-free diet out of a sincere desire to feel better. Not feeling better after going gluten-free is disappointing, but it’s not the end of the rope.

It’s true, exploring these specific sugars can seem very overwhelming. But what they really represent are many new opportunities to feel well again. Best wishes!

If you enjoyed this article, please help others stumble upon this by giving it many claps below or by sharing it. Thanks!

Dr. Emeran Mayer is a world-renowned brain-gut-microbiome expert and Amazon bestselling author of The Mind-Gut Connection. He is currently a Professor in the Departments of Medicine, Physiology and Psychiatry at the David Geffen School of Medicine, Director of the G. Oppenheimer Center for Neurobiology of Stress and Resilience, and Co-director of the CURE: Digestive Diseases Research Center at UCLA.

Dr. Steven Tan is a wellness expert and CEO and co-founder of Selectivor.

Create your free profile on Selectivor! Selectivor is a physician-curated, social food app with over 80 diet templates that helps you to easily organize and share your food preferences and create groups where everyone can eat their way. #Selectivor is how we #EatTogether.



Emeran Mayer MD, PhD

UCLA Brain-Gut-Microbiome Expert, Gastroenterologist, Neuroscientist, and Amazon Best Selling Author of The Mind-Gut Connection.