Eating dietary fiber and whole grains in our food reduces obesity, diabetes type 2, cancer, and cardiovascular disease. Fibers contain a mixture of starches, vitamins, minerals, plant chemicals, antioxidants and are a good energy source.

Dietary fiber includes soluble and insoluble carbohydrates. Soluble fibers resist digestion and absorption in the intestine until they are fermented by bacteria in the large intestine. These fibers dissolve in water, forming a gel. Insoluble fibers do not dissolve in water and resist fermentation in the large intestine. Most fiber-containing foods contain three parts insoluble fiber to two parts soluble fiber.

The Food and Drug Administration (FDA) has approved the claim that the combination of reduced consumption of fats and “increased consumption of dietary fiber from fruits, vegetables and whole grains may reduce some types of cancer”. There is evidence for benefit in treating cancers of the colorectum, small intestine, mouth, larynx, and breast. However, the way in which fiber works is unclear at this time.

A second FDA claim is that diets which are low in saturated fats and cholesterol, while high in fruits, vegetables and whole grains, are associated with lower risk of cardiovascular disease. This refers to dietary fiber intake of 25 to 35 grams/day, with 6 grams being soluble fiber.

Obesity can be reduced by eating dietary fiber. Studies consistently show that increased fiber and whole grain intake leads to weight loss, partly due to reduced energy-producing fats on a high fiber diet. In addition, fibers contain important chemicals such as phenols, carotenoids, lignans, beta-glucan and inulin.

Diabetes is significantly related to dietary fiber intake. The glycemic index measures the ability of different foods to change blood sugar levels. Low glycemic index food means that it causes a smaller rise in glucose or insulin than do other foods. Insoluble fibers can greatly reduce the elevations of blood sugars. A recent study shows that risk of developing diabetes is increased by a poor diet “high in saturated fat, low dietary fiber and high non-structural carbohydrates”.

Foods with a high glycemic index produce higher blood glucose levels. This may lead to reduced insulin release from the pancreas, and the tissues of the body become resistant to insulin. The evidence shows that increasing dietary fiber is more likely to reduce risk of diabetes than a low glycemic index diet.

Fruit and vegetable fibers have shown no effect on the risk of developing diabetes in several studies, whereas, whole cereal grain fiber reduces diabetes significantly. Insoluble fiber has little effect on the absorption of macronutrients, but can reduce appetite and food intake.

Inulin is a fiber component which increases mineral absorption, thereby increasing calcium absorption as much as 20% and increasing bone mineral densities. Inulin acts as a prebiotic, increasing Bifidobacteria in the intestine while reducing pathogenic bacteria. Healthy dietary fibers include arabinoxylan, inulin, beta-glucan, pectin, bran, cellulose, and resistant starches.

CONCLUSION: Fibers are carbohydrates which resist digestion and absorption in the intestine. Their nature provides individual health benefits for the different types of fiber. The FDA supports the claim that “increased consumption of dietary fiber can reduce the prevalence of coronary heart diseases and cancer”. Fiber is also believed to reduce the incidence of obesity and diabetes.

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PMID: 22254008.

Summary #683.