Dietary fiber is the indigestible portion of carbohydrates. Currently, dietary fiber is differentiated by its solubility in water and is designated as either soluble or insoluble. Soluble fiber binds to fat, cholesterol and bile acids and carries them out in fecal waste. Insoluble fiber passes through your gastrointestinal system intact and adds bulk to your fecal waste, increasing the frequency of your bowel movements.
Overall Fiber Recommendations
Adults should eat a minimum of 14g of fiber for every 1,000 calories in their diet, according to the 2010 Dietary Guidelines for Americans. That means that if you eat a 1,500-calorie diet, you should get a minimum of 21g of fiber each day. For a 2,000-calorie diet, you need a minimum of 28g of fiber each day. These recommendations merely represent the minimum of fiber; increased health benefits can be gained with up to 50g of total fiber per day.
Soluble Fiber Recommendations
The National Cholesterol Education Program recommends that adults eat at least 20 to 30g of fiber each day with at least 10 to 25g of soluble fiber. Comparing the recommendations of the NCEP and the 2010 Dietary Guidelines for Americans, you can derive that you need at least 14g of fiber for every 1,000 calories in your diet and at least half of that fiber should be soluble fiber. Therefore, you need at least 7g of soluble fiber for every 1,000 calories in your diet.
Caloric Requirements
Because your dietary fiber needs are based on your caloric requirements, first calculate your caloric requirements. If you have already planned a diet with your doctor or dietitian, use that number of calories to calculate your fiber needs. Otherwise, use the quick rule of thumb dietitians use to estimate caloric needs. For people who wish to lose weight, use 20 calories per kilogram per day. For people who wish to maintain weight, use 25 calories per kilogram per day. For people who wish to gain weight, use 30 calories per kilogram per day. For instance, an 85 kg man who wishes to maintain his weight will need about 2,125 calories per day because 85 times 25 equals 2,125.
Fiber and Soluble Fiber
Using the 2,125-calorie estimated diet, divide by 1,000 and then multiply by 14g of fiber. There are 2.125 calorie units in the diet and each 1,000-calorie unit needs a minimum of 14g of fiber. Knowing that, 2.125 multiplied by 14 equals 29.75, or about 30g of total fiber. Because at least half of the fiber should be soluble fiber, the minimum amount of soluble fiber for an 85-kg man who wants to maintain his weight is about 15g. The complete recommended range would then be 30 to 50g of total fiber. Remember that the maximum amount of fiber each day should be 50g, of which at least 15g should be soluble fiber.
Soluble Fiber Sources
Beans, whole grains, fruit and vegetables are the best sources of dietary fiber. Among those, some foods are especially high in soluble fiber. Black beans, kidney beans, black-eyed peas and lentils are all excellent sources of soluble fiber and total fiber. Apples, apricots, grapefruit, oranges and strawberries are all healthy fruit sources of total fiber and soluble fiber. Asparagus, kale, green peas and Brussels sprouts are healthy vegetable sources. Oatmeal, wheat germ and wheat bran are all healthy grain sources of soluble fiber.
References
- USDA and U.S. Department of Health and Human Services; Dietary Guidelines for Americans: 2010; December 2010
- National Cholesterol Education Program; Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults; National Heart, Lung and Blood Institute; September 2002
- Harvard University Health Services; Fiber Content of Foods in Common Portions; May 2004
- "Advanced Nutrition and Human Metabolism: Third Edition"; James L. Groff, et al.; 2000



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