Does a Gluten-free Diet Improve Metabolic Syndrome Parameters? A Systematic Review

Abstract

To review scientific evidence on the effects of a gluten-free diet on body composition and improvement of clinical and biochemical parameters of metabolic syndrome. The Preferred Reporting Items for Systematic Reviews and Meta-Analyzes - PRISMA guidelines were followed. A literature search was performed in the PubMed, ScienceDirect, Trip Database, Bireme and Scielo databases, without language restriction, until March 2021. The terms “gluten-free diet”, “obesity”, “metabolic syndrome”, and “weight loss”, and Boolean operators (AND/OR) were used. The clinical hypothesis was structured according to the acronym PICOT. Randomized clinical trials with adult and elderly humans without a diagnosis of celiac disease, consuming a gluten-free diet, evaluating associations of the effects of this diet on weight loss and metabolic syndrome components were considered eligible. To assess the risk of bias, the RoB2 was used. A total of 3,198 articles were identified and, after the screening and evaluation of pre-defined eligibility criteria, four studies were included in the qualitative analysis. Weight loss was not associated with a gluten-free diet. However, individuals under a gluten-free diet had lower mean waist circumference, fat percentage (-2.3%) and serum triglyceride levels. The impact of a gluten-free diet on metabolic syndrome parameters is still controversial. In individuals without gluten sensitivity or celiac disease, the consumption of a gluten-free diet appears to provide no nutritional benefit. cholesterol <40mg/ dL). 1 These criteria are also adopted by the I Brazilian Guidelines on diagnosis and treatment of metabolic syndrome 2 and the American Heart Association. 3 The management of MS has been focused on attenuating modifiable risk factors, including overweight/obesity and changes of lifestyle (mainly diet), thereby contributing to the reduction of its incidence and complications. 4 Dietary strategies that have been used in the management of MS include the traditional Mediterranean diet (MD) characterized by a high intake of cereals, vegetables, and olive oil, a moderate intake of fish and alcohol, a low intake of dairy products, red meat, and sweets; 5,6 and the ketogenic diet, composed of 55-65% of fat, less than 20% of carbohydrates and 25-35% of proteins; the lactose-free diet, and the gluten-free diet (GFD). 7 Gluten is an insoluble protein complex, obtained during hydration of two cereal proteins, gliadin and glutenin. It is found in wheat, rye and barley and is source of several nutrients. 8 A GFD excludes foods containing