Dietary fiber (DF) includes the remnants of the edible part of plants and analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the human large intestine. DF can be classified into two main groups according to its solubility, namely insoluble dietary fiber (IDF) that mainly consists on cell wall components, including cellulose, some hemicelluloses, lignin and resistant starch, and soluble dietary fiber (SDF) that consists of non-cellulosic polysaccharides as non-digestible oligosaccharides, arabinoxylans (AX), β-glucans, some hemicelluloses, pectins, gums, mucilages and inulin. The intake of DF is associated with health benefits. IDF can contribute to the normal function of the intestinal tract and it has an important role in the prevention of colonic diverticulosis and constipation. SDF is extensively fermented by gut microbiota and it is associated with carbohydrate and lipid metabolism, with important health benefits due to its hypocholesterolemic properties. Due to these nutritional and health properties, DF is widely used as functional ingredients in food industry, being whole grain cereals, pulses, fruits and vegetables the main sources of DF. Also some synthetic sources are employed, namely polydextrose, hydroxypropyl methylcellulose or cyclodextrins. The DF content of cereals varies depending on cultivars, their botanical components (pericarp, emdosperm and germ) and the processing conditions they have undergone (baking, extrusion, etc.). In cereal grains, AX are the predominant non-cellulose DF polysaccharides followed by cellulose and β-glucans, while in pseudocereals, pectins are quantitatively predominant.

Dietary fiber sources and human benefits: The case study of cereal and pseudocereals

"Diabesity" is the term to illustrate the interdependent relationship between obesity and diabetes. About 80% of the diabetic patients are diagnosed with obesity. Diabesity can be prevented by dietary interventions, especially by incorporating sufficient amount of resistant starch (RS). In the past few decades, RS has inspired the researchers due to its various health benefits. Differing from digestible starch, RS remains undigested in the small intestine, but in the large intestine, it is subjected to fermentation. This review intends to encapsulate the current information related to the dietary RS on diabetes and obesity. RS attenuate hyperglycemic, hyperinsulinemic and hyperlipidemic response in various subjects by restricting gluconeogenesis, bolstering glycogenesis, maintaining glucose and lipid homeostasis and ameliorating pancreatic dysfunction. Various food products were fortified with RS to enhance its dietary intake and were found to exhibit positive impact on human and animal models. This review identified and summarized the research gaps in the available literature.

A critical review on anti-diabetic and anti-obesity effects of dietary resistant starch

Background The starchy crops which normally form the staple diet of people are rich in carbohydrates. People leading a sedentary lifestyle and consuming high amounts of carbohydrate-rich food normally invite obesity and type-II diabetes. Upon digestion of starchy food, postprandial blood glucose level rises rapidly and sharply, which reflects a high glycemic index (GI) value. Scope and approach Various factors affect starch digestibility and the GI of a food or its products. The internal factors such as amylose, lipid, protein, phytic acid, dietary fibre and resistant starch (RS) have been correlated with lower GI value. The external factors which affect GI and starch digestibility include cooking, processing, retrogradation, soaking and germination. Various food matrices are also responsible for alteration in the GI value. Moreover, changes in the environmental conditions including abiotic and biotic stresses are also responsible for the change in starch structure and composition which ultimately affects GI of starchy crops. Key findings and conclusions The GI and starch digestibility of foods are affected by intrinsic and extrinsic factors which affect strategies for management of sugar level to ensure better human health. High amylose, RS, lipid and protein in the food were found to reduce starch hydrolysis. Further, retrogradation, various cooking methods and modification of starch by physical and chemical means resulted in lower GI and increased RS considerably. Analysis and management of postprandial blood glucose level while eating starchy crops would help to understand the risk of diabetes and other lifestyle-related diseases.

Glycemic index of starchy crops and factors affecting its digestibility: A review

https://krishi.icar.gov.in/jspui/bitstream/123456789/19098/1/Pathak%202018-Book%20Rice%20Research%201.1%20NRRI.pdf

Rice Research for Enhancing Productivity, Profitability and Climate Resilience

Background Phytic acid (PA) is an anti-nutrient present in cereals and pulses. It is known to reduce mineral bioavailability and inhibit starch-digesting α-amylase (which requires calcium for activity) in the human gut. In principle, the greater the amount of PA, the lower is the rate of starch hydrolysis. It is reflected in the lower glycemic index (GI) value of food. People leading sedentary lifestyles and consuming rice as a staple food are likely to develop type 2 diabetes. Hence, this study was planned to understand how PA content of different rice varieties affects the GI. Results Rice Khira and Mugai which had very low PA (0.30 and 0.36 g kg-1 , respectively) had higher GI values and α-amylase activity, while Nua Dhusara and the pigmented rice Manipuri black rice (MBR) which had high PA (2.13 and 2.98 g kg-1 , respectively) showed low α-amylase activity and GI values. This relationship was statistically significant, though a weak relationship was found for the pigmented rice. Expression levels of MIPSI, IPKI and GBSSI markedly increased in the middle stage of grain development in all of the six genotypes having contrasting PA and GI. Maximum expression of MIPSI and IPKI was observed in Nua Dhusara and MBR (which had high PA) while that of GBSSI was observed in Khira and Mugai (with higher GI) at middle stage showing a negative correlation between PA and GI. Conclusions The data indicate that high PA content in rice might have an adverse effect on starch digestibility resulting in slower starch digestion in the human gut and consequently low glycemic response. © 2019 Society of Chemical Industry.

Basavdatta Baisakha

Papers

Resistant starch could be decisive in determining the glycemic index of rice cultivars