Dietary fiber is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by their solubility, viscosity, and fermentability, which affect how fibers are processed in the body. Dietary fiber has two main components: soluble fiber and insoluble fiber.
Insoluble fiber: This type of fiber is not soluble in water. Foods that contain insoluble fibers include: wheat bran, whole grain products and vegetables. Insoluble fibers help to regulate bowel movements.
Soluble fibers: These fibers become gummy in water. When eaten, soluble fiber sources slow the passage of food through the digestive system and some researchers believe this action helps to regulate cholesterol and glucose (sugar) levels in the blood by affecting absorption rates. Food sources of soluble fibers are dried beans, oats, barley and some fruits and vegetables. Psyllium is a source of soluble fiber and has been shown to augment the lipid lowering response when combined with other lipid lowering medications. Oat products have the most soluble fiber of any grain. Several recent studies have looked specifically at the effects of oats or oat bran on LDL-C (bad cholesterol). Both oats and oat bran demonstrated favorable results in the lowering of LDL-C. Robitaille's well-known study on overweight pre-menopausal women provided 28 grams of oat bran daily over 4 weeks and not only obtained LDL-C reductions, but also demonstrated an 11.2% increase in HDL-C. The ATP III (Adult Treatment Panel) recommended a minimum of 5-10 grams a day of total dietary fiber for people with even mildly elevated LDL-C levels but higher intakes of 10-12 grams of fiber per day can be more beneficial in those with more severe hyperlipidemia. In large prospective epidemiological studies, total dietary fiber has been shown to protect against coronary heart disease. These studies examined the relationship between whole grain consumption and CHD. Researchers found 20-40% reduction in CHD risk for those who habitually consumed whole grains as compared to those who rarely ate whole grains. There are several mechanisms by which it is believed dietary fiber may protect against CHD. They include lowering serum cholesterol and LDL-C, attenuating blood triglyceride levels, and decreasing hypertension. Fiber consumption also predicts insulin levels and weight gain more strongly than a low total fat and saturated fat diet. High fiber diets may protect against obesity and cardiovascular disease (CVD) by lowering insulin levels. It has been shown that the intake of dietary fiber is inversely correlated with cardiovascular disease risk factors in both sexes. However, most of the evidence shows that a mixture of both soluble and insoluble forms of fiber is an important part of a diet that promotes general good cardiovascular health. Based upon this conclusion, the National Academy of Science recommends 25 grams per day of fiber for women 19-50 years of age and 21 grams per day for women over 50. For men 19-50 years of age, 38 grams per day is recommended and 30 grams for men over 50. This is set from an established 14 grams of fiber per 1,000 calories. The American Diabetes Association's daily recommendations for dietary fiber is 20-35 grams for adults.
There are many sources of high fiber foods. Some example include:
Whole grains: wheat, oats, rice, barley and corn. When shopping, look for food items listed "whole grains" or "whole wheat." Look for breads with a minimum of two grams of fiber (>3 grams is better) per serving and cereals with at least four grams of fiber per serving. Cereals such as Fiber One and Kashi (GO Lean) have greater than 10 grams of fiber per serving.
Fruits and Vegetables: At least five servings per day.
Legumes: Aside from their fiber content, legumes are an excellent source of fiber, vitamins and minerals and protein. Examples of legumes are: lentils, split peas, red and white kidney beans, black beans, navy beans, black-eyed peas, chick peas or garbanzo beans.
Nuts and seeds: While a good source of fiber, they are high in calories and fats and should be eaten sparingly.
Here are some more tips and strategies for increasing fiber:
Start slowly, add a little each day and build up to the recommended level. Simultaneously, add more water to your diet.
Eat vegetables and fruit raw whenever possible. Steam or stir-fry them if you have to cook.
Pureeing doesn't destroy fiber, but juice does not have the fiber of the whole fruit if the pulp has been strained away.
Always start your day with a bowl of high-fiber cereal -- one that has five or more grams per serving.
Put fresh fruit on top of your high-fiber cereal to add another 1 g or 2 g of fiber.
Buy and eat only whole grains. The operative word is "whole." Look for it on the ingredient panel. Wheat bread doesn't mean whole-wheat bread. On average, a slice of whole-wheat bread has 2 g to 3 g of fiber. Choose brown rice instead of white and whole- wheat pasta/noodles instead of white flour, etc.
Add beans to salads, soups and stews.
Add bran cereal to muffins, breads and casseroles. Substitute oat bran for one-third of the all-purpose flour in baking.
When you eat out, ask for fresh fruit instead of dessert.
Have fruit or fresh vegetables for between-meal snack.