Question

1.Explain the general effect of soluble dietary fibers in lowering cholesterol absorption from foods, and in lowering body cholesterol. Why insoluble fibers are not effect? Explain using β-glucan as an example?

2. Discuss the following known health properties of dietary fibers. Your answers should link the property of fibers in producing the stated effect: • Alleviate constipation • Provide satiation • As prebiotics

Answer 1

^1.$\beta$^{-glucan is a soluble fiber which is found in oats in large abundant. It has ability to reduce blood serum LDL cholesterol levels. It has a ability to increase the viscosity of gut contents and thereby modification of absorption rates of nutrients and bile acids.}$\beta$^{-glucan forms a viscous layer in the small intestine. The viscous makes less effective intestinal uptake of dietary cholesterol as well as the re-absorption of bile acid, which the body makes from cholesterol. Lower uptake of cholesterol from the gut combine with more bodily cholesterol use for bile acid production, results in reduce level of cholesterol circulating in the blood. The molecular weight and viscosity of}$\beta$^{-glucan play a significant role in lowering cholesterol.}

Insoluble fiber does not dissolve in water. They do not have an ability to reduce blood serum LDL cholesterol level. They deposit in the body. So the insoluble fiber are not effective in lowering cholesterol absorption.

2. The dietary fibers have a remarkable range of health benefits including the promotion of heart health, stabilization of blood glucose, stimulation of immune response, maintenance of body weight. The link with fibers are discussed below:

(a) Alleviate constipation: Dietary fibers make stool soft. It increase weight and size of stool, so bulky stool is easier to pass which decrease the chance of constipation. Fiber also have to solidify the stool because it can absorb water.

(b) Provide satiation: Satiety is the feeling of fullness that persists after eating. Satiation is important in controlling the amount of energy intake at each meal which is influence by fiber intake

(c) As prebiotics: Dietary fibers work as prebiotics to resists gastric acidity. The fermentation in the colon which change gut microflora is the important mechanism of dietary fibers as prebiotic.