DIETARY FIBERS AND DIABETES (INCLUDING EFFECTS ON POSTPRANDIAL HYPERGLYCEMIA)
Introduction and definitions
Dietary fibers, also known as roughage, are plant portion consisting of complex substances that cannot be fully digested. These substances are mainly carbohydrates and lignin and are resistant to human digestive enzymes. Weickert et al. (2018, p. 439). Dietary fibers are generally classified into two main groups; soluble and insoluble fibers, soluble dietary fibers are those that can dissolve in water. This is fermented in the large intestines to produce gases, and other metabolites such as short-chain fatty acids, this fermentation occur with the help of bacteria that reside in the gut. Soluble fibers are considerably viscous and help create a feeling of fullness, limiting the amount of food one might take in a given period Slavin (2005, p.411). However, there are exceptions to soluble fibers being vicious; an example is in the case of inulin which is found in onions and resistant starches in legumes and banana
Insoluble fibers are those that do not dissolve in water. They are utterly resistant to enzymes of the digestive system in the upper gastrointestinal tract. Insoluble fibers do provide a feeling of fullness. This is especially so for the coarsely ground insoluble fiber, finely ground insoluble fiber can cause constipation.
Dietary fibers are mainly derived from plant sources. Whole grains- those that have their kernel intact have about 12% of mainly insoluble dietary fiber. The pulp of the grain of the plant provides the largest source of soluble dietary fiber. Examples of plants that offer dietary soluble fiber are peas, oats, rye, broccoli, and almonds. Examples of insoluble dietary fiber plant sources are wheat, potato skins, lignans, and unripe bananas, just to mention a few.
Diabetes.
Diabetes is a condition characterized by the body’s inability to regulate blood glucose. This leads to it being too high above the normal upper limit of 7.8 to 11.0 mmol, 2 hours postprandial Salmeron et al. (1997, p. 477). Blood glucose level is regulated by hormone insulin in the body—inadequate or little amounts of insulin. There are two main common types of diabetes, type 1 and type 2 diabetes.
Type 1 diabetes is where the body does not make insulin. This type of diabetes is mostly observed in children and young people but can also appear in older people. People who have this kind of diabetes entirely depend on insulin injections. Type 2 diabetes is characterized by inadequate production of insulin. This is the most common type of diabetes and occurs mostly in older populations. Postprandial hyperglycemia, on the other, is a spike in the level of blood glucose soon after taking a meal.
Dietary fiber and the risk of diabetes
It has been speculated that the effects of high dietary fiber intake can be credited to viscous or gel-forming properties of soluble dietary fiber Wannametheea et al. (2009, p.129). Analyzing results from prospective cohort studies independently for foods rich in soluble dietary fiber and insoluble dietary fiber is anticipated to give stronger protective links for soluble dietary fiber. Still, the available data have not yet supported this. A data analysis that included over 300,000 participants did not show any association of reduced diabetes risk for dietary fiber intake (Schulze et al. 2009). Another study from six pooled prospective cohort studies showed that an increment of 2 servings a day of whole-grain could significantly reduce the risk of getting diabetes by 21% (Munter et al., 2007).
Relationship of dietary fiber and the response of hormones
Dietary fiber intake has been thought to have effects on secretions of some of the digestive tract hormones and give the feeling of being full. Most of the studies done do not show significant changes in satiety ratings. (Robertson. et al., 2003) indicates that the ingestion of soluble vs. an insoluble dietary fiber supplement found no fiber-induced differences of circulating glucagon-like peptide.
The glucose-dependent insulin tropic polypeptide (GIP) is a hormone that is seen to be involved in regulating the metabolism of fat. A study by (Gatenby et al. 1996, p.39) yielded mixed results. Soluble dietary fiber decreased the amount of GIP in people who had diabetes. It was attributed to reduced carbohydrate absorption; in the same study, insoluble dietary fiber intake showed increased responses in biologically active GIP and insulin in healthy subject’s dietary fibers.
Interference of insoluble dietary fiber with the absorption of dietary protein
Insoluble dietary fiber consumption increases whole-body glucose disposal; this is independent of the changes in body weight and was seen in both short- and long-term studies (Kim et al. 2007). Subjects who are resistant to insulin have a higher probability of developing diabetes. So improved insulin sensitivity could be an essential factor contributing to a reduced risk of diabetes in people taking diets rich in insoluble dietary fibers.
Role of dietary fiber intake on influencing postprandial hyperglycemia in comparison to the glycemic index (GI) in carbohydrate-rich foods
GI is a measure of blood glucose. Intake of soluble fiber is linked to the glycemic index as it serves to prevent or delay the absorption of dietary carbohydrates and such reduce the likely hood of occurrence of postprandial hyperglycemia (Russell et al. 2016). Studies done on human and rodents contrast sharply on the beneficial effects of low GI diets. In humans, no consistent, useful results have been shown while in rodents, the intake of low GI diets increased the body fat mass (Isken et al. 2010). it’s an important aspect to consider as increased body fat leads to obesity and is co-morbidity in diabetes.
Improve insulin resistance in people consuming high fiber diets.
(Weickert, 2011) shows that insoluble fiber intake may improve insulin resistance without the person having to lose weight. because they interfere with the absorption of dietary protein. High protein diets may have beneficial effects on satiety, weight loss, and blood lipid but can under certain circumstances increase insulin resistance and risk of getting diabetes Howarth et al. (2001, p.129).
Conclusion.
Studies done show that diets high in insoluble dietary fiber might reduce the risk of getting diabetes significantly. However, it is not all sources of soluble dietary fiber that has been indicated to be beneficial in this way. Cereals and whole grain seem to have a more significant advantage over dietary fibers from fruits and vegetables. There is some evidence that insoluble dietary fibers do interfere with digestion or absorption of dietary protein, but these results are not conclusive and may require further investigation.
It has been demonstrated that dietary fibers intake is linked to better glycemic control and reduced co-morbidity for diabetes as there is an increased insulin sensitivity in people consuming diets high in dietary fiber. Intakes of fiber supplements do not give significant glycemic control, but the consumption of foods rich in dietary fiber can lower blood glucose in type 2 diabetic patients. Dietary fiber intake does help to enhance significantly with increasing insulin sensitivity in hepatic and peripheral tissues in people who are insulin resistant. The effect of dietary fibers on the weight of the subject is not significant in most of the literature review. It is important as obesity and overweight are co-morbidity factors for diabetes.
References
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