Take away Points
In this lesson we learned about fiber. In this closing topic we will simply highlight certain things that are important.
- Soluble fiber dissolves in water in our stomach where it turns into a thick or viscous, substance that looks somewhat like a gel.
- This gel slows down digestion in the intestine give our bodies the time needed to absorb nutrients from food.
- Fruits and vegetables contain some soluble fiber, but the best sources include lentils, beans and peas.
- Insoluble fiber also called roughage does not dissolve in waterÂ
- It remains intact in the gut adding bulk to stools.
- Sources of insoluble fiber include whole grains, nuts, fruits, and vegetables.
- Fermentable fiber also called prebiotic fiber can be either soluble or insoluble
- They are a food source for gut bacteria.Â
- Sources of fermentable fiber include whole grains, fruits, and vegetables.
There is no specific FDA approved recommendation for daily soluble fiber intake. Nutrition labels are also only required to list total dietary fiber grams rather than a breakdown of insoluble and soluble fiber grams. Generally, nutritionists advise that between 20 to 30 percent of our daily dietary fiber should be soluble fiber. For a man, this is about 9.5 grams. For a woman, 6 grams is adequate.Â
For kids between 3 -18 years of age we can use the following formula to estimate the amount of fiber needed. Age + 5 = grams of fiber needed per day. Children less than 3 years should consult their primary provider or a certified nutritionist or dietician for advice. Adolescents over 18 years should follow adult guidelines.
Although there are no FDA approved RDAs for total fiber intake there are Adequate Intake (AI) recommendations.  Adequate Intake is the daily average amount assumed to be adequate for healthy persons. Total fiber, in this context, refers to dietary fiber and functional fiber, fiber in the form of supplements proven to be as functional as fiber.
Age, gender, life stage group | Adequate Intake (grams/day) |
Infants | |
0–6 mo | Not determined |
7–12 mo | Not determined |
Children | |
1–3 years | 19 |
4–8 years | 25 |
Boys | |
9–13 years | 31 |
14–18 years | 38 |
Girls | |
9–13 years | 26 |
14–18 years | 26 |
Types of Fiber | Soluble or Insoluble | Sources | Health Benefits |
Cellulose, some hemicellulose | Insoluble | Naturally found in nuts, whole wheat, whole grains, bran, seeds, edible brown rice, skins of produce. | “Nature’s laxative”: Reduces constipation. |
Inulin oligofructose | Soluble | Extracted from onions and byproducts of sugar production from beets or chicory root. Added to processed foods to boost fiber. | May increase “good” bacteria in the gut and enhance immune function. |
Lignin | Insoluble | Found naturally in flax, rye, some vegetables. | Good for heart health and possibly immune function. Use caution if you have celiac disease or are gluten intolerant. |
Mucilage, beta-glucans | Soluble | Naturally found in oats, oat bran, beans, peas, barley, flaxseed, berries, soybeans, bananas, oranges, apples, carrots. | Helps lower bad LDL cholesterol, reduces risk of coronary heart disease and type 2 diabetes. Use caution if you have celiac disease or are gluten intolerant. |
Pectin and gums | Soluble (some pectins can be insoluble) | Naturally found in fruits, berries, and seeds. Also extracted from citrus peel and other plants boost fiber in processed foods. | Slows the passage of food through the intestinal GI tract, helps lower blood cholesterol. |
Polydextrose polyols | Soluble | Added to processed foods as a bulking agent and sugar substitute. Made from dextrose, sorbitol, and citric acid. | Adds bulk to stools, helps prevent constipation. May cause bloating or gas. |
Psyllium | Soluble | Extracted from rushed seeds or husks of plantago ovata plant. Used in supplements, fiber drinks, and added to foods. | Helps lower cholesterol and prevent constipation. |
Resistant starch | Soluble | Starch in plant cell walls naturally found in unripened bananas, oatmeal, and legumes. Also extracted and added to processed foods to boost fiber. | May help manage weight by increasing fullness; helps control blood sugars. It increases insulin sensitivity and may reduce the risk of diabetes. |
Wheat dextrin | Soluble | Extracted from wheat starch, and widely used to add fiber in processed foods. | Helps lower cholesterol (LDL and total cholesterol),and may lower blood sugar and reduce risk for heart disease; more research is needed. Avoid if you have celiac disease or are gluten intolerant. |
Start slow when introducing more fiber especially soluble fiber into the diet. Switching from a low-fiber to a high-fiber diet quickly can cause a number of problems including abdominal cramps, bloating, diarrhea, flatulence or even constipation. Start by eating high-fiber foods several times weekly then gradually increasing the amount consumed over a two- to three-week period. Drink the appropriate daily amount of water and exercise regularly as this helps to promote regular bowel movements by stimulating intestinal contractions. As always consult your primary care doctor or a certified nutritionist to dietician before and during dietary changes.
Fibers that are soluble and fermentable seem to be the healthiest. Resistant starches are also healthy. Good sources of healthy fibers include vegetables, fruits, oats, legumes, nuts, dark chocolate, avocados, chia seeds and various other foods.  As long as we eat plenty of whole plant foods our fiber intake should take care of itself.