Health benefits of whole grain: effects on dietary carbohydrate quality, the gut microbiome, and consequences of processing

Abstract

Grains are important sources of carbohydrates in global dietary patterns. The majority of these carbohydrates, especially in refined‐grain products, are digestible. Most carbohydrate digestion takes place in the small intestine where monosaccharides (predominantly glucose) are absorbed, delivering energy to the body. However, a considerable part of the carbohydrates, especially in whole grains, is indigestible dietary fibers. These impact gut motility and transit and are useful substrates for the gut microbiota affecting its composition and quality. For the most part, the profile of digestible and indigestible carbohydrates and their complexity determine the nutritional quality of carbohydrates. Whole grains are more complex than refined grains and are promoted as part of a healthy and sustainable diet mainly because the contribution of indigestible carbohydrates, and their co‐passenger nutrients, is significantly higher. Higher consumption of whole grain is recommended because it is associated with lower incidence of, and mortality from, CVD, type 2 diabetes, and some cancers. This may be due in part to effects on the gut microbiota. Although processing of cereals during milling and food manufacturing is necessary to make them edible, it also offers the opportunity to still further improve the nutritional quality of whole‐grain flours and foods made from them. Changing the composition and availability of grain carbohydrates and phytochemicals during processing may positively affect the gut microbiota and improve health.

Beneficial Effects of Partly Milled Highland Barley on the Prevention of High-Fat Diet-Induced Glycometabolic Disorder and the Modulation of Gut Microbiota in Mice

“…Accumulated data indicates that gut microbes and their metabolites are related to the course, prevention, or treatment of obesity, type 2 diabetes, ulcerative colitis, and cancer [43]. Whole grains are associated with the morbidity and mortality of many diseases, which may be due in part to the impact on the intestinal flora [44]. In the present study, PHB supplementation significantly reversed the structure and composition of the gut microbiome in HFD mice to a near-normal status (Figure 3F).…”

Nutritional Properties of Rice Varieties Commonly Consumed in Italy and Applicability in Gluten Free Diet

“…Consequently, it can be useful to better exploit nutritional characteristics of rice varieties. In general, cereals contain carbohydrates, proteins, vitamins, minerals, antioxidants and phytochemicals [18,19]. However, attention should be paid to carbohydrate contents of different cereals and varieties and, in particular, to amylose, one of the components of starch.…”

Process-Induced Changes in the Quantity and Characteristics of Grain Dietary Fiber

“…In non-fermented breads, high fructan concentrations can be obtained [21]. Commonly utilized yeasts (such as Saccharomyces cerevisiae) have invertase (EC 3.2.1.26) activity, leading to partial degradation of fructan during dough mixing and fermentation [14]. Verspreet et al (2013) [168] reported an almost 80% decrease in the fructan content of bread after baking with added yeast and the losses occurred during the mixing and fermentation processes, pointing towards the enzymatic activity rather than the heat treatment as the causal factor.…”

“…Processing involves the use of one or more-unit operations, involving application of mechanical or thermal energy, hydration and often activation of the endogenous biological enzymatic system of the grains. These operations induce various macroscopic to molecular level changes in the grain components, hence affecting the nutritional, technological and sensory properties of the products [11][12][13][14]. While fractionation causes an uneven distribution of DF both in terms of quantity and quality in resulting fractions, additional changes occur in the DF matrix during further processing even without changes in proximate composition.…”