Facts About Fiber


Five fiber sources you should know.

Taking “fiber” isn’t as straightforward as shoppers may think. Your shelves are stocked with numerous different kinds and it’s your job to differentiate them all for shoppers. Here’s a primer on some of the main forms of fibers and what consumers need to know about them.

Soluble versus Insoluble

A basic premise that shoppers should understand is that fiber usually falls into two camps: soluble and insoluble. Soluble fiber dissolves in water; it actually attracts water and becomes gelatinous during digestion, causing the stomach to empty more slowly. This feature is beneficial for supporting even, healthy blood sugar levels. In addition, soluble fibers are said to lower bad cholesterol by inhibiting its absorption (1).

On the other hand, insoluble does just what it sounds like: it won’t dissolve in water and passes undigested through the digestive tract. This helps move things along for digestive support and regularity (1).

While everyone is different, healthy women under 50 should get about 25 g per day of fiber, while men of the same age need 30–38 g daily. Since fiber may affect the absorption of certain medications and blood glucose levels, advise shoppers to talk to their healthcare providers before adding a fiber supplement to their dietary routine.

Types of Fibers

Glucomannan. Often derived from konjac root, glucomannan (GM) is a soluble fiber said to absorb as much as 50 times its weight in water. Experts say GM offers satiety support when taken about 30–45 minutes before meals, which might be of interest to those seeking healthy weight management. In one recent meta-analysis of six trials, researchers report that taking GM may help reduce body weight (2).

Other compelling data suggest GM supports healthy cholesterol and blood sugar levels. In one study of 22 diabetics with high cholesterol, taking 3.6 g/day of konjac GM lowered LDL cholesterol by 20.7%, total/HDL cholesterol ratio by 15.6% and fasting glucose by 23.2% (3). A review of 14 GM studies concurred that GM “appears to beneficially affect total cholesterol, LDL cholesterol, triglycerides, body weight, and fasting blood glucose” (4).

Retailers may also want to tell shoppers that GM may increase bowel movements and might be considered a bulk-forming laxative (5).

Beta-glucans. Found in the cell walls of cereal grains like oats and barley as well as some mushrooms, yeasts and algae, beta glucans are a go-to fiber source for supporting cholesterol and blood sugar in healthy ranges. This soluble fiber is highly viscous and forms a mass in the small intestine that reduces dietary cholesterol absorption and bile acid reabsorption (6).

One recent meta-analysis involving 916 subjects found that “beta-glucan consumption significantly decreased total cholesterol and LDL-cholesterol concentrations but did not affect triglycerides, HDL-cholesterol and glucose concentrations in hypercholesterolemic subjects” (7). Meanwhile, another literature review found that taking 6 g/day of beta-glucans for at least a month improved blood glucose and lipid levels in diabetics (8).

The research behind beta-glucans is so compelling that both the U.S. Food and Drug Administration and the European Food Safety Authority support the use of the claim that oat- or barley-derived beta-glucans can lower cholesterol by 5–8%; those with high cholesterol often report the most benefit (9). And, Health Canada links oat soluble fiber consumption, decreased cholesterol levels and reduced risk of coronary heart disease. Many feel consuming 3 g-day of oat beta-glucan is enough to see this benefit (9).

In addition to these benefits, some believe that cereal beta-glucans have immune-modulating properties and may even support a healthy intestinal microbiota balance by enhancing the growth rate and lactic acid production of certain microbes in the intestines (10).

Psyllium husk. Like beta-glucan, studies suggest psyllium supplementation reduces several metabolic risk factors such as glucose levels, blood pressure and lipid levels (11).

In addition, psyllium is a bulk-forming soluble fiber that promotes digestive regularity by increasing the amount and softness of stool. Since psyllium absorbs water, some people believe it might be beneficial to those with loose stools. Since it is not digested in the small intestine and only partially broken down in the colon, it serves as food for beneficial bacteria (12).

By absorbing water and swelling in the intestinal tract, some believe psyllium also helps shuttle toxins and waste out of the body.  But at the same time, since the added bulk causes food to move more slowly through the digestive tract, digestive enzymes have more time to break down food and release nutrients for absorption into the bloodstream (12). The slower absorption also keeps blood sugar levels from spiking and improves satiety.

Acacia. Not only is acacia a fiber, but it is also a prebiotic, working to restore healthy bacteria in the gut. Some believe it offers the digestive benefits of a bulk-forming fiber and also offers long-term support of a healthy microflora balance in the digestive tract. It is also said to help those with both constipation and diarrhea, though no supplement can cure, treat or prevent any disease (13).

Flaxseed and chia. Omegas-packed flaxseed and chia are sources of both soluble and insoluble fiber. Both have mucilaginous fiber that forms a gel that delays gastric emptying and improves the absorption of nutrients. One tablespoon of chia seeds is said to contain 6 g of fiber, while a tablespoon of ground flaxseed contains 2 g of fiber (14).

Both these seeds contain numerous nutrients and offer many healthy benefits. But, it’s interesting to note that flaxseed has been found in studies to maintain a healthy ratio of LDL to HDL cholesterol and increase HDL cholesterol. Some believe that flaxseed’s soluble fiber content may be the reason for this health benefit (14). WF


1. K.M. Zelman, “Dietary Fiber: Insoluble vs. Soluble,” www.webmd.com/diet/insoluble-soluble-fiber, accessed June 11, 2015.
2. B.M. Zalewski, “The Effect of Glucomannan on Body Weight in Overweight or Obese Children and Adults: A Systematic Review of Randomized Controlled Trials,” Nutrition 31 (3), 437–442 (2015).
3. H-L Chen, et al., “Konjac Supplement Alleviated Hypercholesterolemia and Hyperglycemia in Type 2 Diabetic Subjects—A Randomized Double-Blind Trial,” J. Am. Coll. Nutr. 22 (1), 36–42 (2003).
4. N. Sood et al., “Effect of Glucomannan On Plasma Lipid And Glucose Concentrations, Body Weight, And Blood Pressure: Systematic Review And Meta-Analysis,” Am. J. Clin. Nutr. 88 (4), 1167–1175.
5. Constipation, Life Extension Mag, http://www.lifeextension.com/Protocols/Gastrointestinal/Constipation/Page-03, accessed June 12, 2015.
6. I.D. Nwachukwu, et al., “Cholesterol-Lowering Properties of Oat Β-Glucan and the Promotion of Cardiovascular Health: Did Health Canada Make the Right Call?” Appl. Physiol. Nutr. Metab. 40 (6), 535–542 (2015).
7. X. Zhu, et al., “Quantitative Assessment Of The Effects Of Beta-Glucan Consumption On Serum Lipid Profile And Glucose Level In Hypercholesterolemic Subjects,” Nutr. Metab. Cardiovasc. Dis. 2015 Apr 29. (Epub ahead of print).
8. E. Francelino Andrade et al. “Effect Of Beta-Glucans In The Control Of Blood Glucose Levels Of Diabetic Patients: A Systematic Review,” Nutr. Hosp. 31(n01), 170–177 (2014).
9. D. Webb, “Betting on Beta-Glucans,” (16) 5, 16 (2014), www.todaysdietitian.com/newarchives/050114p16.shtml, accessed June 12, 2015
10. M.P. Arena, et al., “Barley β-Glucans-Containing Food Enhances Probiotic Performances of Beneficial Bacteria,” Int. J. Mol. Sci. 15(2):3025–3039 (2014).
11. S. Pal and S. Radavelli-Bagatini, “Effects of Psyllium on Metabolic Syndrome Risk Factors,” Obes. Rev. 13 (11), 1034–1047 (2012).
12. Yerba Prima, www.yerba.com, accessed June 12, 2015.
13. “Adam’s Corner: Fiber,” http://debrasnaturalgourmet.com/fiber-part-iii-final, accessed June 12, 2015.
14. World’s Healthiest Foods, www.whfoods.com/genpage.php?tname=foodspice&dbid=81, accessed June 12, 2015.

Published in WholeFoods Magazine, August 2015, (online 7/16/2015)