Gluten-Free Diet Side Effects to Expect


When you start the gluten-free diet, side effects can include changes in your weight (either gains or losses), improvements in your energy level, and boosts to your nutritional status. In many cases, these side effects are beneficial.

However, the gluten-free diet also can cause undesirable side effects. For example, you may find you suffer more from constipation since many gluten-free foods contain little fiber. You also may find you get dramatically more sensitive to gluten cross-contamination in the food you eat.

Wondering what to expect in the way of side effects as you start the gluten-free diet? Here's what you should know.

Your Weight May Change

woman weighing herself
Flashpop / Getty Images

Regardless of whether you start out underweight or overweight, your weight likely will trend toward normal levels once you're diagnosed with celiac disease and begin following the gluten-free diet.

While many people think everyone newly diagnosed with celiac is underweight, studies have shown that most are a normal weight, while many are overweight. For example, one study found about 61 percent of newly diagnosed celiacs were considered normal weight, 17 percent were underweight for their height, and 22 percent were overweight or obese.

Following their diagnoses, the underweight patients tended to gain weight, while the overweight and obese patients tended to lose weight. The normal weight celiacs tended to stay at a normal weight.

Therefore, if you're overweight or underweight at diagnosis, you might expect to see your weight tend to normalize as a side effect of the gluten-free diet. However, if you indulge in too many gluten-free snack foods (which tend to be high in calories and low in nutrition, just like their conventional counterparts), you could find yourself packing on a few unwanted pounds. So be careful.

Your Lactose Intolerance May Improve


Many newly-diagnosed celiacs cannot digest lactose, the sugar found in milk and milk products, such as ice cream and yogurt. That's because of the intestinal damage caused by celiac disease—our intestinal villi are responsible for digesting lactose, and when they're destroyed by the reaction to gluten in our diets, we can't digest lactose anymore. So you may find yourself dairy-free as well as gluten-free.

However, as your intestinal damage (technically known as villous atrophy) begins to heal, you may begin to tolerate lactose-containing foods again as a side effect of your gluten-free diet. Expect this change to be gradual, especially if your lactose intolerance has been severe—try very small amounts of milk products at first to see how your body reacts.

Symptoms of lactose intolerance include diarrhea, gas, and bloating, so if you experience these after a large serving of a milk product, back off for a while before trying again. You also can try reduced-lactose or lactose-free milk to see if your body reacts better to those products.

If you're not eating dairy products, make sure you're getting enough calcium in other ways, such as by taking a gluten-free vitamin supplement.

You May React Badly to Gluten Cross-Contamination


When you were eating gluten every day, you likely didn't react to individual instances of gluten ingestion. However, once you remove it from your diet, you may find your body reacts somewhat violently to gluten cross-contamination in your food—or to a bite of that gluten-filled cake that you simply couldn't resist. This is one of the most surprising gluten-free diet side effects.

A reaction to gluten in your food may come quickly (within a half-hour in some cases), or it may not appear until the next day or even later. Your digestive symptoms may come in the form of diarrhea, constipation, abdominal pain, reflux, gas, or even vomiting. Meanwhile, you may also experience other symptoms, including fatigue, joint pain, brain fog, and even bouts of depression due to gluten.

All this from a crumb? Yes, our body's somewhat strenuous reactions to gluten-containing foods can be a bit startling once you've gone gluten-free. Still, don't be alarmed if you get these recurrent symptoms—and take a look at these tips for recovering from an accidental glutening.

Once you can function again, scrutinize your diet to see where you may be getting hidden gluten.

Remember to always play it safe and cook gluten-free recipes.

You May Not Get Enough Fiber in Your Diet

assortment of beans on spoons
Westend61 / Getty Images

Whole grain bread products provide the bulk of the fiber in most people's diets. But when you give up gluten, you're left with fewer whole grain products from which to choose—unfortunately, many gluten-free breads and other baked goods don't contain very much fiber, and so consuming too little fiber is a common gluten-free diet side effect.

This situation is improving somewhat, and some gluten-free bread brands are producing breads made with whole grains. However, getting enough fiber on a gluten-free diet still represents a bit of a challenge, and some people suffer from constipation because they aren't getting enough fiber in their diets.

So what can you do? You can try adding sources of fiber to your diet. For example, you can look specifically for whole-grain gluten-free bread, and consider adding more beans and legumes, plus fresh fruits and vegetables, to your plate. Nuts and seeds also are high in fiber and make easy take-along gluten-free snacks.

If you bake your own bread (as some of us do), you may want to consider grinding your own flour from whole gluten-free grains—here's a list of five interesting gluten-free grains to try, many of which are high in fiber. You also can take a gluten-free fiber supplement.

Whatever you do, don't add copious amounts of fiber to your diet all at once, since that much fiber can upset your digestive tract and cause bloating.

If you're still struggling with constipation or are concerned that you're not getting enough fiber, talk to your doctor about your options.

You Should Watch Your Nutrients

vitamin-rich fruits in test tubes
Oscar Burriel / Getty Images

Prior to going gluten-free, many of us got some of our iron and B vitamins from enriched wheat flour products. Because those products obviously are off-limits on the gluten-free diet, some people don't get enough of those nutrients while eating gluten-free (most gluten-free baked products are not fortified with extra vitamins and minerals).

You should pay particular attention to your intake of thiamin, riboflavin, niacin, and folic acid (all B vitamins), along with your iron intake, to make sure you're getting the recommended daily allowances.

You can load up on fresh fruits and vegetables (many contain high levels of B vitamins), you can try gluten-free cereals (many of which are fortified), or you can consider taking a supplement to make up for any nutritional shortfalls that occur as a side effect of the gluten-free diet.

A Word from Verywell

weight loss
Terry Vine / Getty Images

Obviously, some of these gluten-free diet side effects are welcome (weight loss when you're overweight, for example). But others may not be welcome at all. It's no fun to get more sensitive to trace gluten, for example.

As you're working your way through the first few months, keep in mind that even though the diet represents a major lifestyle change (and carries a pretty steep learning curve), you likely can expect these side effects to settle down eventually.

If you find you're still struggling with constipation or nutrient levels after six months or so on the gluten-free diet, talk to your doctor about a referral to a dietician who specializes in the diet.

That person can help you identify problem areas and correct them.

Was this page helpful?
Article Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.