Elsevier

Nutrition

Volume 32, Issues 7–8, July–August 2016, Pages 777-783
Nutrition

Applied nutritional investigation
Is it gluten-free? Relationship between self-reported gluten-free diet adherence and knowledge of gluten content of foods

https://doi.org/10.1016/j.nut.2016.01.021Get rights and content

Highlights

  • Unintentional gluten ingestion is common among persons with celiac disease.

  • Persons with celiac disease had difficulty determining whether foods contain gluten.

  • Self-reported diet adherence did not correlate with knowledge of gluten in food.

  • Misconceptions regarding gluten in food may lead to unintentional gluten exposure.

Abstract

Objective

To assess the relationship between self-reported adherence to a gluten-free diet (GFD) and the ability to determine correctly the appropriateness of particular foods in a GFD.

Methods

Persons with celiac disease were recruited through clinics and support groups. Participants completed a questionnaire with items related to GFD information sources, gluten content of 17 common foods (food to avoid, food allowed, and food to question), GFD adherence, and demographic characteristics. Diagnosis was self-reported.

Results

The 82 respondents (88% female) had a median of 6 y GFD experience. Most (55%) reported strict adherence, 18% reported intentional gluten consumption and 21% acknowledged rare unintentional gluten consumption. Cookbooks, advocacy groups, and print media were the most commonly used GFD information sources (85–92%). No participant identified correctly the gluten content of all 17 foods; only 30% identified at least 14 foods correctly. The median score on the Gluten-Free Diet Knowledge Scale (GFD-KS) was 11.5 (interquartile ratio, 10–13). One in five incorrect responses put the respondent at risk of consuming gluten. GFD-KS scores did not correlate with self-reported adherence or GFD duration. Patient advocacy group members scored significantly higher on the GFD-KS than non-members (12.3 versus 10.6; P < 0.005).

Conclusions

Self-report measures which do not account for the possibility of unintentional gluten ingestion overestimate GFD adherence. Individuals who believe they are following a GFD are not readily able to correctly identify foods that are GF, which suggests ongoing gluten consumption may be occurring, even among patients who believe they are “strictly” adherent. The role of patient advocacy groups and education to improve outcomes through improved adherence to a GFD requires further research.

Introduction

Celiac disease and dermatitis herpetiformis are chronic autoimmune conditions treated by elimination of all sources of dietary gluten [1], [2]. Following a gluten-free diet (GFD) is challenging and although most patients self-report strict dietary adherence, a significant number have persistent mucosal damage 2 y after starting a GFD [3]. Even in the absence of symptoms, persistent mucosal damage is clinically significant because it is associated with greater risk of severe complications of celiac disease, including malignancy [4], as well as with increased all-cause mortality [3]. Reasons for persistent mucosal damage are likely multifactorial. Potential reasons include occult gluten ingestion due to lack of awareness of gluten content of foods [5], contamination of allegedly gluten-free foods [6], [7], and factors intrinsic to underlying celiac disease and its natural history [8], [9].

Gluten ingestion due to lack of awareness of the gluten content of foods may be a significant issue for many individuals, but has the potential to be modified. Determining whether a food contains gluten is challenging. Gluten is a component of many ingredients, thus it is often not explicitly listed on product labels. Within specific food categories (e.g., potato chips), certain brands may be gluten-free while others may contain trace amounts of gluten and thus should be avoided [10]. Even within a brand, some flavors may contain gluten while others are gluten-free. The products available and the composition of particular products also changes. For example, some companies have adjusted the recipe for popular breakfast cereals to offer gluten-free versions [11]. For these reasons, following a gluten-free diet is a dynamic process that requires continuous review and reassessment.

Patients with celiac disease use many different information sources to learn about gluten-free diets [12]. These include experts (e.g., dietitians, nutritionists, and physicians), the Internet, patient support groups, and print media. There is no standardized education source for individuals requiring a GFD. Regardless of the source of a patient's technical information about gluten-free diets, this knowledge must be applied to the practical daily decisions of what to eat and, equally important, what not to eat. In practice, GFD knowledge is frequently applied in the context of attention to the content of processed foods. Few studies have assessed GFD knowledge or evaluated its relationship to self-reported adherence [13], [14]. This has particular clinical relevance as misunderstandings regarding the gluten content of foods could account for (unrecognized) gluten exposure and persistent mucosal damage [5].

Efforts to maintain a stringent GFD are tempered by practical, cultural, and social realities. Individuals may choose to avoid any products that potentially contain gluten, thereby eliminating many common foods from their diet. This may result in adverse effects such as social isolation [15], [16] or specific nutrient insufficiencies. This contrasts with the exponential increase in availability and diversity of gluten-free foods. Consequently, individuals trying to follow a GFD must balance vigilant avoidance of gluten containing products with awareness of new gluten-free foods as well as of alternate grains (which may or may not contain gluten) which were not previously available.

In this study, we aimed to assess the relationship between self-reported GFD adherence and the ability to determine correctly the appropriateness of particular foods in a GFD among a community sample of individuals with celiac disease and/or dermatitis herpetiformis trying to follow a GFD.

Section snippets

Methods and materials

From October 2011 through October 2012, adults trying to follow a GFD were recruited through the local celiac support group, specialist clinics and advertisements at retail locations specializing in gluten-free products. Interested individuals accessed an anonymous online questionnaire. This study includes adults who reported following a GFD for a medical diagnosis of celiac disease or dermatitis herpetiformis. The questionnaire included items related to personal demographic characteristics,

Results

Of the 82 participants who completed the questionnaire, 76 had celiac disease and six had both celiac disease and dermatitis herpetiformis (Table 1). The majority (88%) were female and most were older than 55 y of age. Median GFD duration was 6.0 y (interquartile ratio [IQR] 2–10 y).

Discussion

Individuals with celiac disease with or without dermatitis herpetiformis exhibited significant deficits in their knowledge of the gluten content of different foods. Those who reported “strict adherence” to a GFD were as likely as other respondents to misidentify the gluten content of a variety of foods. Thus, although they may be scrupulous about what they eat, “strict” adherers appear at equal risk of unwittingly consuming gluten. Indeed, a study of patients with putative “non-responsive

Conclusions

While it is generally recognized that it can be difficult to determine if food is gluten-free, it is equally challenging for the health care professional to determine whether an individual's diet is gluten-free. Traditionally, the most common approaches have been patient self-report and assessment by a skilled dietitian with training in gluten-free diets. Both of these methods rely upon the patient's own knowledge of a GFD. In this study, we demonstrated that patients with celiac disease trying

Acknowledgment

The authors thank the people with celiac disease who generously gave their time to complete the questionnaire. This study would not have been possible without their support.

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    All authors contributed to the conception and design of the study; generation, collection, assembly, analysis and/or interpretation of data; and drafting or revision of the manuscript. All authors reviewed and approved the final submitted manuscript. This study was supported by the Canadian Celiac Association JA Campbell Award. J.S. received postdoctoral fellowships from the Canadian Institutes of Health Research and the Manitoba Health Research Council. These sponsors did not have any role in study design; the collection, analysis and interpretation of data; the writing of the report; or in the decision to submit the article for publication.

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