There is considerable scientific evidence linking many health conditions to a lack of dietary fiber especially a number of factors that lead to heart disease such as insulin resistance, type 2 diabetes, obesity, high blood pressure, and elevated cholesterol levels. A new analysis of 18 studies involving over 670,000 subjects provides even more details on the importance of eating a high fiber diet to prevent against heart attacks and strokes.
Dietary fiber refers to the components of the plant cell wall, as well as the indigestible residues. The composition of the plant cell wall varies according to the type of food. In general, most plant cell walls contain 35% insoluble fiber, 45% soluble fiber, and 20% other components such as lignans (beneficial compounds linked to protecting against many forms of cancer).
Much of the focus on the heart health benefits of dietary fiber has focused on the soluble fiber type found in vegetables, fruit, legumes, and oats while the insoluble fiber found in grains like wheat have shown beneficial effects on digestive tract health.
Soluble dietary fiber helps prevent heart disease in a number of important ways, including helping to fight weight gain and improve insulin sensitivity, lowering cholesterol, and assisting in eliminating toxic dietary and environmental compounds.
Table. Diseases Highly Associated with a Low-Fiber Diet
Metabolic Obesity, gout, diabetes, kidney stones, gallstones
Cardiovascular High blood pressure, strokes, heart disease, varicose veins, deep vein thrombosis, pulmonary embolism
Colonic Constipation, appendicitis, diverticulitis, diverticulosis, hemorrhoids, colon cancer, irritable bowel syndrome, ulcerative colitis, Crohn’s disease
Other Dental caries, autoimmune disorders, pernicious anemia, multiple sclerosis, psoriasis, acne
Researchers sought to better understand the association between coronary heart disease (CHD) and dietary fiber intake by examining the results from eighteen studies involving 672,408. From this data, they were able to assess the impact of different types of dietary fiber, as well as a dose-response relationship.
In assessing the likelihood that an individual will develop a certain disease, specialists in epidemiology (observational and statistical studies of people and diseases) use number known as relative risk. Relative risk (abbreviated RR) is a number that shows how much more likely it is that individuals who possess a certain trait will develop a condition, compared with individuals who do not share that trait. For example, someone with a RR of 1.5 is 50 percent more likely to develop a condition than someone whose RR is 1. A relative risk of 0.5 means your risk is 50% less.
Results showed the pooled-adjusted RRs of death due to CHD for the highest versus lowest category of fiber intake was 0.83 – representing a 17% reduction in death due to CHD. Further subgroup analyses based on fiber subtypes (cereal, fruit, and vegetable fiber), indicated that RRs were 0.81, 0.68, and 0.91 respectively.
These results indicate that dietary fiber from fruit intake offered the greatest impact on reducing CHD mortality. Higher fruit fiber intake reduced CHD mortality by 32%.
Foods rich in dietary fiber are also rich in a great number of other beneficial compounds that fight heart disease including plant antioxidants, magnesium, and potassium. In particular, fruit that are rich in plant flavonoids exert benefits in protecting the lining of blood vessels and the prevention of atherosclerosis (hardening of the arteries). The flavonoid components are likely more important in protecting against CHD than the fiber.
Here are some key dietary recommendations to help fight heart disease:
• Increase the consumption of a wide variety fiber-rich plant foods (fruits, vegetables, grains, legumes, and raw nuts and seeds).
• Eat two servings of high flavonoid fruit each day (berries, cherries, citrus, grapes, etc.).
• Eat less saturated fat and cholesterol by reducing or eliminating the amounts of animal products in the diet.
• Increase the consumption of monounsaturated fats (e.g., nuts, seeds, and olive oil) and omega-3 fatty acids.
• Follow a low-glycemic diet.
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Wu Y, Qian Y, Pan Y, et al. Association between dietary fiber intake and risk of coronary heart disease: A meta-analysis. Clin Nutr. 2014 May 28. pii: S0261-5614(14)00140-X. [Epub ahead of print]