Fiber and cardiovascular disease risk: how strong is the evidence?

Dietary fiber consists of edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine. Fiber can be classified as a dietary source (eg, cereal, fruit, vegetable, or legume) or as a supplement. Based on chemical properties, fiber can be divided to water-soluble (eg, beta-glucans, pectin, and guar) and insoluble (eg, cellulose and lignin) forms. An increasing number of observational findings have reported a lower incidence of coronary heart disease in subjects who report consuming diets high in fiber. Dietary fiber is thought to affect several cardiovascular disease (CVD) risk factors. Soluble fiber decreases serum total and low-density lipoprotein cholesterol concentrations and improves insulin resistance. The effect of fiber on inflammatory markers and coagulation is not yet well established. While soluble, gel-forming fiber has beneficially affected CVD risk factors, food sources of mainly insoluble fibers, primarily contributed by cereal products, have been the most consistently associated with lower incidence rates of CVD. Despite this contradiction, the evidence promotes a food-based approach favoring increased intake of whole-grain cereals, fruit, and vegetables providing a mixture of different types of fibers for CVD prevention.