7 things to know about gluten on a keto or low-carb diet
Should you worry about gluten? That’s a question many people have asked themselves over the years.
Those with a serious medical condition called celiac disease must avoid gluten completely.
But over the last couple of decades, researchers have been probing whether people without celiac disease who have similar symptoms should also avoid gluten. This has been a remarkably difficult topic to categorize epidemiologically, in part because social media and the lay press have popularized the phenomenon of non-celiac gluten sensitivity, leading many people to self-diagnose and place themselves on a gluten-free diet.1
Anecdotally, many of these people have reduced symptoms without gluten in their diets. But randomized clinical trial (RCT) data show that the complete story is much more nuanced regarding whether the main problem is gluten or other components of wheat-containing foods. (Fortunately, if you are following a grain-free low-carb diet, chances are you have already eliminated any potential offending agent.)
For example, studies have often demonstrated a significant nocebo effect, in which the placebo causes adverse symptoms just as often or more so, as compared to gluten.2 Trials have also found that there are other substances (e.g. fructans) found in wheat and other gluten-containing foods that cause symptoms more often than gluten itself.3
All of the above evidence notwithstanding, there are also clinical trials that have attempted to dissect out the confounding variables. Some of these trials have found that there is a small proportion of self-identified subjects with gluten sensitivity who appear truly sensitive.4
Regardless of whether the controversial diagnosis of non-celiac gluten sensitivity is as prevalent as the internet would suggest, the topic is well-worth discussion. This guide will address what gluten is, its effects on our health, and whether we should avoid it.
1. What is gluten?
Gluten proteins, such as gliadin and glutenin, are found in grains such as wheat, barley, and rye. Gluten does not provide any essential nutrients for the body if sufficient amounts of protein are consumed from other sources.
Gluten is a “flexible” protein and can be manipulated easily. So, although it’s a natural part of some grains, gluten is now frequently added to packaged and processed foods to enhance texture and flavor. It also enables dough to rise and helps to bind foods together. Think pizza dough.
The precise mechanism of gluten sensitivity is unclear, but it is thought to be related to changes in intestinal permeability, caused by gluten or other components of wheat, leading to an immune response. Some studies also show a change in the gut microbiome.5
2. What foods contain gluten?
Gluten is commonly found in carbohydrate-rich foods such as bread, baked goods, crackers, pasta, cereals, and most processed and packaged foods.
Although oats don’t contain gluten, most commercial oats are cross-contaminated with gluten from contact with other grains during harvesting and processing. This can include oat fiber, an ingredient used in some low-carb recipes.6
Other foods that may surprisingly contain gluten are some soups, commercially-prepared bouillon and broths, cold cuts, processed cheese (e.g., Velveeta), mayonnaise, soy sauce, salad dressings, and sausage.
Gluten-free alternatives for most of these products are available. If you have a gluten sensitivity, make sure to check the labels when purchasing these types of products.
3. What are the different types of conditions associated with gluten intolerance?
There is a spectrum of known gluten-related conditions ranging from wheat allergy to celiac disease, all related to an immune response to gluten.
The most severe type of gluten disorder is known as celiac disease. Studies suggest this condition affects less than 1% of the world’s population.7
Celiac disease is an autoimmune response to gluten where immune cells start to attack other cells or tissues of the body. This can lead to inflammation, damage to the lining of the intestine, and a reduced ability to absorb nutrients.8
The onset of symptoms is usually gradual and may take months or years to develop after the introduction of gluten. Symptoms include diarrhea, gas, bloating, fatigue, and weight loss. Celiac disease may also be associated with other conditions such as osteoporosis and iron-deficiency anemia due to poor absorption of critical nutrients.
Certain individuals with a genetic predisposition are at increased risk of developing celiac disease, but only a small percentage actually develop it. There may be other environmental triggers in addition to genetics and exposure to gluten, but the exact sources have not been identified.
Wheat allergy is a fairly common food allergy, estimated to affect 0.2 to 1% of pediatric populations.9 Symptoms are those typically associated with a food allergy, such as swelling, rash, nausea, vomiting or diarrhea. Much less common is difficulty breathing or anaphylaxis.10
Non-celiac gluten sensitivity
As described in the introduction of this guide, non-celiac gluten sensitivity is a controversial diagnosis; in fact, some authors suggest a more accurate description would be non-celiac wheat sensitivity. This accounts for the copious evidence suggesting that other substances often found in wheat-containing foods (e.g. fructans, FODMAPs, and amylase trypsin-inhibitors) may be responsible for people’s sensitivities.11
The true prevalence of non-celiac gluten sensitivity is unknown, as most estimates come from studies looking at how many people self-identify as having the problem, or how many people are following a gluten-free diet for any reason at all.12
The onset of symptoms, including digestive distress, usually occurs hours to days after gluten exposure. In addition, studies have shown this condition can lead to an overall reduction in quality of life measures.13
It’s often hard to differentiate non-celiac gluten sensitivity from other gastrointestinal conditions such as irritable bowel syndrome, as there is no test to diagnose this type of gluten sensitivity.
Therefore, diagnosis is made by exclusion of other gluten-related or gastrointestinal disorders. In most people, symptoms disappear after removing gluten from the diet for a few weeks, with little to no lasting effects.
The only available treatment for gluten-related conditions is a gluten-free diet, as the offending nutrient causing harm needs to be removed.14 The good news is that whether the sensitivity is to gluten or other components of wheat, eliminating wheat tends to solve the problem.
4. Why does gluten get such a bad rap?
Gluten continues to be demonized by many health-conscious individuals. But does it deserve this reputation?
For those with celiac disease, gluten definitely deserves the bad rap. These individuals have an autoimmune reaction to gluten that can cause many health troubles, as discussed above.
But is gluten “bad” for those without celiac disease or a true allergy to wheat?
Although many people think that gluten-containing foods play a role in causing or worsening an array of non-gastrointestinal symptoms (headaches, fatigue, depression, etc.), there is a lack of solid evidence. The strongest statement that can be made regarding gluten’s association with other health problems is that, in people with suspected non-celiac gluten sensitivity, gluten might exacerbate some of their pre-existing symptoms.
There is speculation that changes to the methods of processing gluten-containing foods or an increase in gluten intake may be responsible for the rising prevalence of gluten-related conditions.15
However, given that there are several other substances in gluten-containing foods that may actually be responsible for people’s adverse reactions, it seems prudent to focus more on the types of food that contain gluten and related substances, as opposed to gluten itself.16
5. How do I know if I have an issue with gluten?
If you have chronic problems with diarrhea, bloating, anemia, rashes, and/or fatigue, you should talk to your doctor about screening blood work to test for celiac disease.17 A positive screening test will usually be followed by a visit to the gastroenterologist to discuss doing a biopsy of the small intestine, which is the definitive way to make the diagnosis.
If your screening for celiac disease is negative, but you have many of the same symptoms when eating gluten-containing foods, then you may choose to remove these foods from your diet and wait for your symptoms to fully resolve. Then, slowly reintroduce these foods to see if the symptoms recur; this can be done multiple times. Foods that reliably provoke symptoms should probably be avoided.
Remember, it may be difficult to pinpoint if symptoms are being caused by gluten or some other component of these foods. A series of different food tolerance tests may be your best bet.
For instance, if you do just fine with gluten-containing homemade bread but have symptoms after eating processed gluten-containing products from the store, the main offender may not be gluten. But if you react poorly to both of these, then there is a higher likelihood that gluten could be the problem.
6. Should I avoid gluten or eat gluten-free foods even if I am not intolerant?
The trend of individuals reducing or eliminating gluten from their diets is increasing worldwide.18
Although a gluten-free diet is a necessity for people with celiac disease and recommended for those with gluten intolerance, people without diagnosed gluten issues are also excluding it from their diets because they believe it healthier to do so.
Many claim to lose weight or experience other improvements in health when cutting out gluten, but there is no solid evidence to support this strategy.19
Gluten free does not necessarily mean healthier
Despite the health claims for eating gluten-free, no scientific evidence supports weight loss with a gluten-free diet or suggests that the general population would benefit from avoiding gluten for health reasons.20
Although many people think that a gluten-free diet is healthier and more nutritious, the opposite may be true, as many products marketed as “gluten-free” are highly processed.
These gluten-free foods are often made with refined grains and additives such as tapioca starch, less commonly fortified with folic acid and iron, and have less fiber and more sugar compared to regular gluten-containing foods.21
In fact, several studies have actually found a tendency toward weight gain and obesity among those who follow a gluten-free diet.22
In addition, highly-processed gluten-free diets that are high in refined carbohydrates are often deficient in important nutrients such as iron, zinc, vitamin D, and protein.
We suspect that these drawbacks would be significantly attenuated by eating a whole-foods, minimally processed gluten-free diet.
The bottom line is that since we don’t need gluten, there’s likely no harm in avoiding it. And if you think you are sensitive to it, you can always consider removing it from your diet to see if symptoms improve.
But in the end, it may be more about eliminating gluten-containing foods rather than the gluten itself.
As with any diet, when eliminating certain foods or nutrients, you still have to pay attention to what replaces it. Eating processed gluten-free food is not automatically healthier than a potentially less processed gluten-containing version.
7. Gluten and low-carb or ketogenic diets
Since gluten is most commonly found in carbohydrate-containing foods, low-carb and ketogenic diets are almost always low in gluten. A keto diet, in particular, is usually gluten-free because foods containing gluten have too many carbs to fit within the diet.
However, you may find that some low-carb and keto foods contain a small amount of gluten, especially jerky, sausages, soups and broths. If you suspect you have a gluten sensitivity, you may want to consider less-processed or gluten-free versions.23
The bottom line is that a low-carb or ketogenic diet is a great alternative for individuals with gluten or other carbohydrate-related intolerances. Plus, you may see numerous other potential benefits from carbohydrate reduction such as weight loss, improved metabolic health, and more.
Clinical Gastroenterology and Hepatology 2017: Suspected Nonceliac Gluten Sensitivity Confirmed in Few Patients After Gluten Challenge in Double-Blind, Placebo-Controlled Trials [systematic review of randomized trials; strong evidence]
This RCT showed that reducing FODMAP foods made a much more significant impact on symptoms than avoiding gluten:
Gastroenterology 2013: No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates[randomized trial; moderate evidence]
Nutrients 2016: Evidence for the Presence of Non-Celiac Gluten Sensitivity in Patients with Functional Gastrointestinal Symptoms: Results from a Multicenter Randomized Double-Blind Placebo-Controlled Gluten Challenge[randomized trial; moderate evidence]
This RCT showed a reduction in symptoms with administration of gluten-digesting enzymes:
Clinical and Translational Gastroenterology 2018: Combination of Gluten-Digesting Enzymes Improved Symptoms of Non-Celiac Gluten Sensitivity: A Randomized Single-blind, Placebo-controlled Crossover Study[randomized trial; moderate evidence]
Nutrients 2017: A New Proposal for the Pathogenic Mechanism of Non-Coeliac/Non-Allergic Gluten/Wheat Sensitivity: Piecing Together the Puzzle of Recent Scientific Evidence [overview article; ungraded]
Oat products that are labeled gluten-free will usually meet the acceptable standard for non-contamination. ↩
BMC Gastroenterology 2021: Non-celiac wheat sensitivity: rationality and irrationality of a gluten-free diet in individuals affected with non-celiac disease: a review [overview article; ungraded] ↩
The proportion of the population following a gluten-free diet has grown over the past 10 years, presumably due – at least in part – to the common perception that avoiding gluten is “healthy” and good for weight loss.
Nutrients 2016: Evidence for the presence of non-celiac gluten sensitivity in patients with functional gastrointestinal symptoms: results from a multicenter randomized double-blind placebo-controlled gluten challenge [randomized trial; moderate evidence]
Although this novel study administered gluten-digesting enzymes and found improvements, there is no well-standardized medication available for this purpose.
Clinical and Translational Gastroenterology 2018:Combination of Gluten-Digesting Enzymes Improved Symptoms of Non-Celiac Gluten Sensitivity: A Randomized Single-blind, Placebo-controlled Crossover Study[randomized trial; moderate evidence]
As stated earlier, it is impossible to determine the true prevalence of non-celiac gluten sensitivity, given that most surveys are counting people who have either self-diagnosed or have decided to follow a gluten-free diet for other reasons. Nonetheless, these numbers have been increasing over the past decade. ↩
As stated earlier, fructans, FODMAPs, and amylase trypsin-inhibitors have all been implicated as more likely to be the causes of GI symptoms in people with non-celiac gluten sensitivity. Since many foods that contain gluten also contain fructans, FODMAPs, and amylase trypsin-inhibitors, the treatment is usually the same — eliminate wheat and grains. So, from a practical standpoint, it may not matter what the underlying cause is as long as you can eliminate the trigger. ↩
The typical screening tests are a TTG IgA antibody and a total IgA level. ↩
European Journal of Gastroenterology and Hepatology 2014: A UK study assessing the population prevalence of self-reported gluten sensitivity and referral characteristics to secondary care [observational study, weak evidence] ↩
One reason why there may be so many anecdotes of people feeling better after cutting out gluten is because it is found in a large proportion of processed foods. Cutting out processed food – not gluten – is likely the helpful variable.
At Diet Doctor, our recipes don’t use ingredients known to contain gluten because it can cause problems for people sensitive to it, even in small amounts. In spite of this, we can’t guarantee that some ingredients used in our recipes (ground psyllium husk, oat fiber and protein powder, etc.) haven’t been contaminated during production. ↩