The Difference Between Soluble and Insoluble Fiber

 insoluble vs soluble fiber

You’ve probably heard a thousand times that you should increase your fiber intake. But do you really know why you should follow this advice? Fiber is one of those important yet under-appreciated nutrients. Find out why upping your fiber consumption should be one of your health priorities this year.

Fiber Facts

Popularly dubbed as ‘nature’s broom,’ dietary fiber, or roughage, is a type of carbohydrate that is completely absent in animal foods and can only be found in whole plant foods such as fruits, vegetables, nuts, seeds, whole grains, sprouts, and legumes. Unlike other types of carbohydrates, fiber cannot be absorbed by your body. Fiber’s inability to get completely degraded in the gastrointestinal tract is what makes it very beneficial to the human body. It mops up noxious substances in your digestive system.* The colon is one of the body’s major organs of elimination. Toxins and metabolic wastes are dumped there day in and day out, including millions of cells that die everyday. Fiber helps reduce the amount of decomposing cells, carcinogens, and toxic debris found in the inner walls of the colon such as those that come from charred meat and deep-fried foods.* Fiber slows down the digestion of food in the stomach but speeds up transit time of digested food in the intestines and colon.* This is why fiber-rich foods and fiber supplements are recommended for constipation due to its ability to promote bowel regularity.*

Insoluble and Soluble Fiber

There are two main types of fiber: soluble fiber and insoluble fiber. All whole plant foods actually contain both soluble and insoluble fiber; some just contain more soluble than insoluble fiber and vice versa.  Insoluble fiber helps to promote regularity and may improve gastrointestinal health.*  Food sources of insoluble fiber include: cherries, dates, cantaloupe, grapes, tomatoes, wholegrain products (pasta, bread, and other baked goods made with wholegrain flour), nuts, seeds, whole wheat, brown rice, broccoli, cauliflower, dark leafy greens, and green beans.

Soluble fiber, as its name suggests can be dissolved partially in water. It becomes viscous or gel-like upon contact with water. Soluble fiber ferments in the stomach and acts as a prebiotic, a type of plant fiber that encourages the growth of probiotics or beneficial gut microorganisms.*   Studies show that soluble fiber can assist in weight control by curbing appetite and potentially reducing food intake.* The higher the fiber content of a food, the greater its satiety index is. This means it helps you feel full for longer, which leads to the avoidance of overeating and unnecessary snacking.*  Soluble fiber can be an effective detoxifying agent by absorbing circulating toxins found in bile and thus promoting better absorption of nutrients.*

There are many kinds of soluble fiber. Perhaps the most notable type is inulin. Found in onion, leeks, garlic, chicory root, bananas, wheat, yacon, jicama, artichoke, and asparagus, inulin is a prebiotic that helps put good bacteria in charge.  Prebiotics such as inulin work by stimulating the growth of probiotics by feeding them and creating an ideal environment for them to thrive in. Studies conducted on prebiotics have been promising. The nutrient has been observed to produce positive physiological effects on gastrointestinal and calcium absorption.  It also helps improve intestinal motility. Some foods that contain soluble fiber: various fruits like apples, bananas, and oranges; many beans like kidney, black, and lima; veggies like broccoli, carrots, Brussels sprouts, Chicory Root; and oats like oatmeal, oat cereal, and oat bran.  Low fat diets rich in fiber-containing grain products, fruits, and vegetables may reduce the risk of some types of cancer (a disease associated with many factors).

How to Increase Fiber Consumption

The Institute of Medicine’s current recommendation for fiber intake is 14 grams for every 1,000 calories of food eaten each day. That would be at least 25 g for women aged 50 and below and 21 g for those above 50. Men aged 50 and below are recommended to consume at least 38 g fiber whereas those older than 50 should consume enough plant foods that will help them meet their minimum requirement of 30 g a day.  Unfortunately, statistics show that half of Americans consume around half the fiber they need.  Here are a few tips to get some much needed fiber into your system:

  1. Do your best to meet the daily recommended intake of 5-13 servings of fruits and vegetables.
  2. Try to consume whole fruits (e.g. orange instead of orange juice; olives instead of olive oil), seeds (sesame seeds in lieu of sesame oil), and nuts (macadamia nuts instead of macadamia oil) to get more fiber and nutrients. Fruit juice and culinary oils are plant-based but are devoid of fiber due to the refining process they have undergone.
  3. Skip refined carbohydrates and opt for brown rice, red rice, wild rice, quinoa, and whole grain pasta made of whole wheat, brown rice, or quinoa flour.
  4. Drink enough water to prevent dehydration caused by sudden increased intake of fiber. Water also helps fiber move along the gastrointestinal tract.
  5. Try wholegrain products fortified with chicory root such as wholegrain cereals and snack bars.

Fiber is a powerful nutrient that can do a tremendous amount to boost your health.*  While it is always preferable to meet your nutritional needs from diet, supplementation might be needed to get you to the levels recommended by experts in the field of nutrition.  Just be sure to check with your healthcare professional before adding any supplements to your diet.

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