Best food groups: Legumes, whole grains, fruits, vegetables
Also consider: Sapodillas, figs, elderberries, quinoa, guavas, loganberries, prunes, pumpkin, dates, coconut
What is insoluble fiber and why is it so important? Insoluble means that it does not dissolve in water and consequently is not absorbed into the body. The main types of insoluble fiber are cellulose, hemicellulose, and lignans, which help aid digestion by moving food through the digestive tract and helping stool absorb water. Insoluble fiber provides bulk and softens stool, which helps reduce hemorrhoids and diverticular disease.
Did you know? High-fiber foods contain 5 g or more per serving, with good fiber sources ranging from 2.5 to 4.9 g per serving. Research shows that dietary fiber, particular insoluble fiber derived from whole grains, can help reduce the risk of colorectal cancer by as much as 40 percent. Fiber can be a great aid in weight loss, as it adds volume to food and can extend the time spent chewing on foods; that is, increased volume plus longer chewing time equals satiety (feeling full and satisfied).
How much is enough? The amount of total fiber recommended a day by the Institute of Medicine is 14 g for every 1,000 calories consumed. Another way of looking at it is that women and men under fifty should consume 25 and 38 g of dietary fiber, respectively, and those over 50 should consume 21 and 30 g per day, respectively. The reason for the lesser amount is the assumption that older folks eat fewer calories. Ironically, constipation is often one of the most complained-about gastrointestinal illnesses among those over the age of fifty!
To date, there isn't a specific recommendation for just insoluble intake, just an encouragement to eat a variety of foods to meet fiber needs.
It's a double-edged sword. Not enough insoluble fiber can lead to constipation and too much can cause loose and watery stools. Too much fiber can also increase intestinal gas (flatulence), and cause bloating and abdominal cramps. These feelings will go away over time as either the body adjusts to the new intake of fiber or the amount of fiber is reduced. However, it may not be wise to greatly exceed the dietary recommendations for fiber, as it can reduce the absorption of minerals such as calcium, iron, magnesium, and zinc.
Supplements: Fiber supplements come in a variety of shapes, sizes, and forms that are typically made from wheat bran, purified cellulose, or powdered psyllium husks. Fiber supplements could have negative interactions with prescribed medications, so getting your fiber from a wide variety of fruits, vegetables, legumes, and whole grains might be the best choice when it comes to increasing fiber intake.
1. Lentils
Lentils are an excellent source of fiber, and also contain resistant starch, which may benefit blood glucose regulation and cholesterol management and may help fight colon cancer. In a study of 186 men and women, results revealed that those who ate legumes, such as lentils, had a much lower risk of developing colon polyps, which are associated with the development of colon cancer.
2. Split Peas
Be they green or yellow, because of their high fiber content, split peas are great for helping lower cholesterol and manage blood-sugar disorders. A large study that followed more than sixteen thousand middle-aged men found that those who consumed legumes had an 82 percent reduction in risk for coronary heart disease.
3. Soybeans
Adult diabetics who were given a dry-roasted soybean supplement had significantly reduced fasting glucose and triglycerides in comparison with the control group. Also, the soybean supplement group showed enhanced antioxidant activity, which may contribute to protection against oxidative damage in type 2 diabetes.
4. Wheat Bran
Wheat bran, the outer covering of the wheat kernel, is arguably one of the healthiest by-products in the food industry, yet until this century it was discarded until its dietary benefits were realized. It is now typically made into cereals, bran muffins, and can be used as a supplement to foods such as yogurts, smoothies, salads, or other items, to add crunch and nutrition. Wheat bran is an excellent source of iron, magnesium, niacin, phosphorus, selenium, and zinc, and an excellent source of riboflavin and thiamine. It can be used for a variety of digestive woes from constipation to irritable bowel syndrome and helps waste move through the digestive tract quickly and smoothly. It may also benefit cholesterol, blood pressure, and type 2 diabetes.
5. Pinto Beans
Phenolic acids and flavonols may play important roles on the overall anti-oxidant activities of pinto beans; however, these can be significantly reduced in standard cooking methods. Steaming may be a preferred way of cooking pintos after they are soaked.
Pinto means "painted" in Spanish. But when cooked, pinto beans lose their mottled appearance.
6. Chickpeas
An Australian study found those subjects who made chickpeas a regular part of their diet ate less processed food and high-calorie snacks because they reported that they felt satiated (satisfied). They also reported that their bowel habits were the best when they ate chickpeas.
Chickpeas are the basis of such internationally famous dishes as Middle Eastern hummus, chana masala from India, and panelle from Sicily.
7. Raspberries
Fiber is not usually the first thing you think of when it comes to the nutritional properties of raspberries, but they do pack a bunch of it! Raspberries provide important anti-inflammatory nutrients called anthocyanins (the pigments in red, purple, and blue fruits), which may help curtail cardiovascular disease and diabetes and improve eyesight and memory.
The seeds of raspberries are of great interest to the cosmeceutical industry. The oil in raspberry seeds is rich in vitamin E and omega-3 fats, and surprisingly, may help protect skin, as the oil has an SPF (sun protection factor) of 25 to 50.
Source: CRC Handbook of Dietary Fiber in Human Nutrition, 3rd Edition
USDA National Nutrient Database for Standard Reference, Release 24