Fiber and Disease Prevention

Introduction

Fiber provides many health benefits, from decreasing heart disease to improving digestion. Unfortunately, most U.S. adults and children consume less than 50% of the recommended amount of dietary fiber. Adults should consume 20-35 grams of fiber per day. Read below to find out the many dietary sources of fiber.

What Exactly is Fiber? And How does it Work?

Fiber is a carbohydrate that the body cannot readily digest by enzymes in the gut. In other words, unlike other carbs like white bread/pasta or rice, fiber is NOT broken down into tiny sugar molecules. Instead, it passes through the body undigested. As such, it can help regulate blood sugar levels and hunger. 

And not all fibers are the same. There are two types:

1. Soluble Fiber – these fibers partially dissolve in water. They lower blood glucose and cholesterol. Examples: apples, pears, berries, nuts, legumes, beans, dried peas, oatmeal, and oatbran.
2. Insoluble Fiber – these fibers do NOT dissolve in water. They help with digestion and prevent constipation. Examples: carrots, tomatoes, zucchini, celery, cucumbers, brown rice, whole wheat bread, barley, couscous.

What are the Best Sources of Fiber?

A wide variety of foods can help incorporate fiber into your diet. Here’s a list, divided by food type, in alphabetical order (* refers to the top 3 in that food category in fiber amount):

Remember to drink plenty of water when adding fiber to your diet in order to prevent fecal impaction. In addition, add high-fiber foods gradually to your diet to minimize gastrointestinal symptoms (cramps, diarrhea, flatulence and borborygmus, i.e. rumbling stomach sounds)

Health Benefits

Fiber is associated with a reduced risk of heart disease, diabetes, diverticular disease and constipation. Contrary to popular belief, however, fiber has little effect if any on colon cancer risk.

1. Heart Disease. Coronary artery disease is the #1 cause of death of men and women in the U.S. The blood vessels supplying the heart, the coronary arteries, get ‘clogged’ with cholesterol-filled plaques; this is called “atherosclerosis”. A completely blocked artery is unable to deliver oxygen and nutrients to the heart which leads to a heart attack (myocardial infarction). Studies have shown that a diet high in fiber lowers the risk of heart disease. Fiber lowers the cholesterol level in blood, and also improves high blood pressure.
2. Type 2 Diabetes. In spite it being a carbohydrate, fiber does NOT increase blood sugar (glucose) levels because it is not broken down by the body. Thus, it is beneficial in people with diabetes. Many scientific studies (including Harvard research with female nurses and male health professionals) have shown that diets high in cereal fiber and low in high-glycemic index foods were associated with a lower risk of developing type 2 diabetes.
   
3. Gastrointestinal Health. Did you know that constipation is the #1 gastrointestinal complaint in the U.S.? High-fiber diets relieve constipation. Dietary fiber (particularly insoluble fiber) was associated with a 40% lower risk of developing diverticular disease (diverticulitis is inflammation of the intestines). Dietary fiber, however, is NOT associated with reduced risk of colon cancer or colon polyps.
4. Healthy Weight Loss. Meals high in fiber tend to be less “energy-dense” thus have fewer calories for the same volume of low-fiber foods. High-fiber foods also typically make a meal seem larger – they stay in our GI system longer, slow down our rate of digestions, and keep you feeling full longer.
   

REFERENCES
American Heart Association http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/HealthyDietGoals/Whole-Grains-and-Fiber_UCM_303249_Article.jsp
Anderson JW et al. Nutr Rev. 2009 Apr;67(4):188-205 http://onlinelibrary.wiley.com/doi/10.1111/j.1753-4887.2009.00189.x/pdf
Harvard School of Public Health http://www.hsph.harvard.edu/nutritionsource/fiber-full-story/
Joslin Diabetes Center http://www.joslin.org/info/how_does_fiber_affect_blood_glucose_levels.html
Mayo Clinic http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/in-depth/high-fiber-foods/art-20050948
Medscape http://www.medscape.com/viewarticle/410677_3