Food Intolerance: Fact and Fiction

Separating the wheat from the gluten

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Once upon a time, when having a dinner party, the only accommodation a thoughtful host had to make was to consider the occasional vegetarian. But times certainly have changed.

Tamara Duker Freuman
Tamara Duker Freuman

Nowadays, it seems everyone has a restricted diet of some sort. Some people avoid milk for a variety of reasons—either due to lactose intolerance, an inability to digest the milk sugar in dairy products, or concerns that dairy makes them congested. Gluten—the main protein found in wheat—is increasingly being shunned by health-conscious consumers who believe it to be a "toxin" responsible for everything from bloating and weight gain to poor energy and "brain fogs." And the latest newcomer to the food intolerance scene is fructose—the primary sugar in fruit juice, honey, agave nectar, and high-fructose corn syrup—which research suggests may be poorly digested in up to 30 percent of the Caucasian population.

It seems we're a nation suffering from a case of collective indigestion. And it raises a few important questions. What is a food intolerance? Is food intolerance truly on the rise? Is there something real behind this trend, or is it all in our minds?

Unlike true food allergies, which involve a systemic and potentially life-threatening immune response to the protein in an offending food, a food intolerance tends to trigger symptoms which are unpleasant, but not dangerous per se. While food allergies only affect an estimated 1 to 4 percent of adults in the United States, experts believe that adverse reactions to food that do not involve the immune system—sometimes called food sensitivities or food intolerances—may affect significantly more people. These non-immune food intolerances may result from poor digestibility due to low enzyme levels, as is the case with lactose intolerance, or from an adverse chemical reaction to naturally-occurring components in foods or their preservatives, such as with histamine or sulfite sensitivity. To complicate matters, reliable tests to diagnose a non-immune food intolerance are only available for a small number of foods, which makes assessing the existence of these conditions a largely subjective exercise.

While it's anyone's guess as to whether the actual prevalence of non-immune food intolerances is increasing, there are some compelling reasons to think they could be. As American diets include more and more processed foods, our intake of staple processed ingredients like wheat and fructose is also increasing. Average per capita intake of fructose appears to have increased by an estimated 32 to 48 percent between the late 1970s and 2004, according to the National Health and Nutrition Examination Survey, conducted through the Centers for Disease Control and Prevention. Experts also point out that the quality of the ingredients we eat has changed. As U.S. News has previously reported, food engineering has increased the average percentage of gluten in wheat from 4 percent to about 14 percent, according to Alessio Fasano, director of the University of Maryland Center for Celiac Research. Our processed diets also contain more preservatives and artificial chemicals, some of which have been implicated in triggering adverse chemical reactions in susceptible people. Some speculate that while small quantities of any of these ingredients would not be problematic, repeated exposure to high amounts of them may expose the fault lines of our old-fashioned digestive systems, which have not evolved as fast as our modern diets.

Since so many of the common food intolerances are to ingredients encountered in processed foods, however, it's easy to implicate the wrong suspect for symptoms like low energy or bloating. Wheat and sugar-based snacks tend also to have a high-glycemic index, which means they spike blood sugar levels and can result in an energy crash soon after eating them. And nutrition bars, diet foods, and cereals increasingly contain an indigestible fiber called inulin (chicory root extract), which can make some people feel gassy and bloated. If you experience symptoms after eating foods like these, it's tempting to blame them on the wheat gluten, though in reality, gluten may not be at fault.

Adding fuel to the fire are the restaurants, food companies, and marketers of popular "detox cleanses," whose offerings of "free-from" foods is exploding. It seems these players are both responding to and creating the increased consumer demand for foods without popular villains like dairy, gluten, soy, and fructose. Additionally, an expensive blood test which claims to measure "food sensitivities" by looking at antibodies in the blood called immunoglobulin G, or IgG, may be convincing more folks that they, too, have food intolerances. While the test seems to be growing in popularity, no mainstream medical bodies have endorsed its use for diagnostic purposes, and scant reliable scientific evidence exists to support its utility in pinpointing food intolerances.

If you suspect a food intolerance, try keeping a detailed food and symptom journal for two weeks that includes times, foods, portion sizes, and any symptoms experienced. Then, bring your journal to a gastroenterologist or registered dietitian who can evaluate the relationship between the timing of your symptoms and food(s) eaten. If a food intolerance is suspected, you may be referred for a breath test (if available) or systematic elimination diet of suspected culprits. It may take some detective work, but getting a reliable answer to your question will help you avoid only the foods necessary to feel your best.

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Tamara Duker Freuman, MS, RD, CDN, is a NYC-based registered dietitian whose clinical practice specializes in digestive disorders, Celiac Disease, and food intolerances. Her personal blog,, focuses on healthy eating and gluten-free living.