The Gluten-Free Diet Epidemic: Socioeconomic Factors Predict Google Search Trends More Than Health-Related Factors

Abstract

Introduction: The gluten-free diet has gained popularity over the last 10 years, out of proportion to shifts in diagnosis and incidence of celiac disease. Similarly, there has been a rapid growth in the popularity of “gluten-free diet” as a Google search term. We tested whether regional socio-demographic and health data predicted the popularity of Google searches for “gluten-free diet” compared to other diets. Methods: Google Trends data were obtained regarding which dietary terms were most commonly searched from 2005 to 2015 across 210 Nielson designated market areas (DMAs) in the US. Terms included Atkins diet, gluten-free diet, low-calorie diet, low-carbohydrate diet, low-fat diet, organic food diet, Paleolithic diet, South Beach diet and veganism. We used Cox proportional hazards to identify regional predictors of searches for the gluten-free diet (2005-2015). Variables included median household income, racial/ethnic composition, prevalence of diabetes or obesity, level of leisure-time physical inactivity, and limitations in access to healthy food (aggregated from the US Census American Community Survey (ACS), Center for Disease Control and Prevention Diabetes Interactive Atlas, and County Health Rankings National Data). Years until “gluten-free diet” became the most frequent search was used as the time parameter in Cox models. Results: “Gluten-free diet” was the most popular dietary search in 4 of 210 DMAs (1.9%) in 2006. This increased to 199/210 DMAs (95%) by 2015. We categorized DMAs into quartiles for median household income (Q1: $29,951-$42,008, Q2: $42,009-$45,621, Q3: $45,622-$51,403, Q4: $51,404-$81,123) and percent of non-Hispanic white residents (Q1: 4-60%, Q2: 61-76%, Q3: 77-86%, Q4: 86-96%) using ACS 2007 data. On multivariate analysis, both were associated with shorter time to gluten-free diet being the top search term (see Figure 1). Health variables such as prevalence of diabetes or obesity were not. The hazard ratios for Q2, Q3, and Q4 of median household income compared to Q1 were 1.78 (95% CI 1.09-2.92), 2.50 (95% CI 1.44-4.33), and 3.00 (95% CI 1.64-5.47) respectively. For percent of non-Hispanic white residents, hazard ratios for Q2, Q3, and Q4 were 1.64 (95% CI 1.02-2.64), 2.33 (95% CI 1.40-3.89), and 4.14 (95% CI 2.40-7.14) respectively.Figure: Multivariable analysis comparing quartiles of socio-demographic factors (ex. median household income and proportion of residents who were non-Hispanic white) and health-related factors (ex. diabetes prevalence, obesity prevalence, levels of leisure-time physical inactivity, and limitations in access to healthy food) are associated with “glutenfree diet” being the most popular regional diet-related Google Search term annually. HR=Hazard Ratio; CI=Confidence Interval.Conclusion: Google searches for “gluten-free diet” are associated with socio-demographic characteristics, such as income and racial/ethnic composition, more than health-related factors.