“What is fiber?”
Essentially, fiber (or dietary fiber) refers to plant materials which cannot be digested by the stomach and small intestines of humans. Fiber is typically divided into two groups based on physical characteristics: Soluble (dissolve in water or absorb water) and Insoluble (do not dissolve in water); however, in the near future, insoluble and soluble may no longer be used to describe fiber types. Instead, fiber may be classified based on its physiologic effects (Salvin, 2005). Most foods of plant origin contain a mixture of both fibers.
“Why is fiber good for me?”
Fiber assists with a number of bodily functions including regularity and reduction of blood cholesterol. Fiber consumption has a positive effect on weight loss and preventing weight gain. (Salvin, 2005) As one observational study on fiber consumption and weight loss concluded: “Regardless of fat intake, participants who consumed the most fiber gained less weight compared with individuals who consumed the least amount of fiber (Salvin, 2005).” As well, “populations that report higher fiber consumption also demonstrate lower obesity rates (Salvin, 2005).” Other proposed benefits of dietary fiber consumption are listed in Figure 1.
Figure 1: benefits of dietary fiber consumption (adapted from Salvin, 2005)
“How much fiber should I be eating?”
Current recommendations for fiber intake are 38 g/d (grams per day) for men and 25 g/d for women (Salvin, 2005). You can also calculate fiber requirements using caloric intake: individuals should consume 10 to 13g of fiber per 1000kcal (or Calories) consumed. Table 1 provides an easy reference for fiber intake. Foods high in fiber include most fruits, vegetables, whole grains and beans/legumes. Although a diet that meets the recommendation for fiber intake has many benefits, too much fiber can decrease the energy density of the diet, reduce nutrient absorption, and if the diet is not adequate in fluid, cause constipation. (Grosvenor & Smolin, 2002)” Thus, if you are consuming a high fiber diet make sure to drink plenty of water.
(Salvin, 2005)
Some tips for increasing fiber intake:
Ø Eat whole fruits instead of drinking fruit juices.
Ø Replace white rice, bread, and pasta with brown rice and whole-grain products.
Ø Choose whole-grain cereals for breakfast.
Ø Snack on raw vegetables instead of chips, crackers, or chocolate bars.
Ø Substitute legumes for meat two to three times per week in chili and soups.
Ø Experiment with international dishes (such as Indian or Middle Eastern) that use whole grains and legumes as part of the main meal (as in Indian dahls) or in salads (for example, tabbouleh)
(http://www.hsph.harvard.edu/nutritionsource/fiber.html)
“I am on low-carbohydrate diet. Am I getting enough fiber?”
The answer is: probably not. Studies of the most popular high protein, low carbohydrate diets show insufficient dietary fiber content. Diets such as the Zone and Protein Power have fiber intakes of 18.1 g (consuming 1600kcal/day) and 10.6g respectively (Salvin, 2005). Two of the most popular low-carb diets today are Atkins and the South Beach Diet (Salvin, 2005). Both diets are described as being extremely low in dietary fiber (Table 2) - less than 10g/d! If you are on a carbohydrate restrictive diet you should ensure that you are consuming enough fiber through fruits, vegetables, beans/legumes, nuts, seeds, whole grains (bran) and/or supplementation.
(Salvin, 2005)“Which Foods are high in fiber?”
In general most fruits, vegetables, nuts, seeds, whole grains (bran) and beans/legumes are relatively high in fiber. The website below contains a list of some popular food items and their fiber content.
http://www.fatfreekitchen.com/fiberlist.html
For more information visit: http://www.hsph.harvard.edu/nutritionsource/fiber.html
References:
Slavin, JL. Dietary fiber and body weight. Nutrition 21 (2005) 411-418
Grosvenor, MB. & Smolin, LA. Nutrition: From Science to Life. Toronto: Harcourt Publishing, 2002.
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