Glycemic Index of Gluten-Free Bread and Their Main Ingredients: A Systematic Review and Meta-Analysis

Abstract

This study aimed to perform a systematic review and meta-analysis of the glycemic index (GI) of gluten-free bread (GFB) and its main ingredients. The systematic review followed PRISMA guidelines, using seven electronic databases (PubMed, EMBASE, Scopus, Science Direct, Web of Science, gray literature research with Google Scholar, and patents with Google Patent tool), from inception to November 2020. Eighteen studies met the inclusion criteria evaluating 132 GFB samples. Five articles tested GI in vivo, eleven in vitro; and two studies tested both methods. The analysis showed that 60.7% (95% CI: 40.2–78.1%) of the samples presented high glycemic indexes, evidencing a high glycemic profile for GFB. Only 18.2% (95% CI: 11.7–27.2%) of the bread samples presented in the studies were classified as a low GI. Meta-analysis presented moderate/low heterogenicity between studies (I2 = 61% and <1% for both high and low GIs) and reinforced the proportion of high GIs. Lower GIs were found in formulations based on Colocasia esculenta flour or enriched with fiber, yogurt and curd cheese, sourdough, psyllium, hydrocolloids, enzymes, fructans, and resistant starch, highlighting the efficacy of these ingredients to lower GFBs’ GI. GFB tends to present high GI, impacting the development of chronic diseases when consumed.

Sourdough Microbiome Comparison and Benefits

“…In the International Tables of Glycaemic Index and Glycaemic Load values [ 157 ] and several scientific papers [ 38 , 39 , 40 ], it is reported that sourdough bread has lower GI than yeast bread. Whilst most gluten-free breads also tend to be high in GI due to low contents of fiber, micronutrients and protein, the sourdough is claimed to be one of the ingredients which reduces GI when being incorporated into gluten-free bread [ 158 ]. The study by Romão et al [ 158 ] deduced that Lb.…”

“…Whilst most gluten-free breads also tend to be high in GI due to low contents of fiber, micronutrients and protein, the sourdough is claimed to be one of the ingredients which reduces GI when being incorporated into gluten-free bread [ 158 ]. The study by Romão et al [ 158 ] deduced that Lb. plantarum -based sourdough possesses lower GI than W. cibaria -based ones.…”

The Role of Hydrocolloids in Gluten-Free Bread and Pasta; Rheology, Characteristics, Staling and Glycemic Index

“…The glycemic index is influenced by several factors such as starch granule, bread structure and viscoelasticity. It was previously reported that the glycemic index of GF bread is much higher compared to the traditional bread, exerting an influence over chronic diseases [ 47 , 48 , 49 ]. The strategies to reduce the glycemic response of starchy gluten-free products refers to the replacement of flours and starches with alternative raw materials (characterized by an increased content of dietary fiber, protein and resistant starch), the addition of viscous dietary fibers and application of different processing conditions such as grain germination, sourdough fermentation or hydration level [ 50 , 51 , 52 ].…”

Oat-Based Foods: Chemical Constituents, Glycemic Index, and the Effect of Processing

“…GI became an effective tool to assess the relative effects of various oat products. Several researchers have reviewed the GI of foods such as gluten-free bread and products made from starchy crops [10,11]. Oats are habitually regarded as the low-GI ingredients, but the GI value is collectively determined by chemical composition and processing conditions.…”