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Dietary fiber is a diverse group of plant materials that cannot be broken down (digested) by human enzymes or absorbed in the small intestine. In the large intestine (colon) fiber is partially or completely fermented by the gut microbes to produce short-chain fatty acids (SCFA) and various gasses.  SCFA have long been known to have an important physiological role in gastrointestinal and metabolic health. The most recent research points to a new and far-reaching role SCFA might play in reducing inflammation and thus in promoting the overall health. Production of gas during fiber fermentation can lead to side effects, such as abdominal discomfort, excess gas and bloating.


High-fiber diets have a multitude of health benefits. Fiber helps with weight loss, contributes to cardiovascular and gastrointestinal health, normalizes cholesterol and blood glucose. Many of these health gains are a result of the effect that dietary fiber has on enriching and maintaining good bacteria in the gut. Healthy and diverse gut flora has 

Health benefits of high fiber diet in IBS, constipation relief, glycemic control

positive on metabolism, immune system, even our mood, and brain function (research on the gut-brain axis that describes communication between gut microorganisms and brain function has attracted a lot of attention and excitement)! On the other hand, compromised gut ecosystem has been associated with gastrointestinal problems and obesity.


Fiber can be classified into different groups depending on their properties, such as water solubility, fermentability, and viscosity. The most commonly used division is into soluble and insoluble fiber. Soluble fiber forms a viscous gel with water and is well fermented in the colon. Insoluble fiber is poorly fermented but provides bulk necessary to move the waste down the digestive system. Plant foods contain both soluble and insoluble fiber in varying ratios.


The best way to get fiber is through food. Excellent sources of fiber are legumes (beans, peas, lentils), whole wheat, oat, bran, barley products, flaxseeds, artichokes, broccoli, prunes, raspberries, figs. Institute of Medicine recommends that adults younger than 50 consume 25 grams (women) and 38 grams (men) of fiber a day. Adults older than 50 years of age need less fiber, and the recommended values are set as 21 grams for women and 30 grams for men. However, more than 90% of adults do not meet the recommended intake, averaging only 16 grams per day.

Fiber Supplementation in Irritable Bowel Syndrome (IBS)


A recent review of 14 clinical trials investigating the use of fiber in IBS found soluble fiber, psyllium in particular, to be effective in improving IBS symptoms.


Psyllium is a fiber found in the husks of the Plantago ovata seed. As a soluble, partially fermentable fiber, psyllium can help in IBS in several ways:


  •  It acts as a stool bulking agent with a laxative effect

  •  SFCA produced by psyllium fermentation can reduce inflammation and have a beneficial effect on intestinal wall health

  • Psyllium can act as a prebiotic, feeding and maintaining the good bacteria in the colon.


Fiber Supplementation for constipation relief


A number of clinical trials investigated the efficacy of fiber in treating constipation. The most recent systematic review of these studies found that psyllium improves stool frequency and consistency.   Evidence for other types of fiber, such as wheat bran and methylcellulose, is still lacking.


Fiber for glycemic control


Although a mixed group of materials, dietary fiber is mostly made up of carbohydrates (this is why on a food label dietary fiber is listed in that category). Unlike other carbohydrates, the ones that constitute dietary fiber are not digested in our bodies and thus do not increase blood glucose levels. However, consumption of fiber alongside digestible carbohydrates modifies the way they are processed in the body. Soluble fiber that forms gel-like substance with water slows down stomach emptying and macronutrient absorption, resulting in reduced postmeal (postprandial) glucose level as well as total and LDL (“bad”) cholesterol levels. On the other hand, insoluble fiber found in bran cereal and whole grains seems to reduce diabetes risk.


The results of 35 clinical studies indicate that supplementation with psyllium improves glycemic control both in diabetic and prediabetic patients.  In addition to a direct effect on the blood glucose level, psyllium can help manage prediabetes and diabetes by regulating body weight. As such, psyllium is considered a valuable addition to the lifestyle changes in diet and exercise, often recommended for diabetic and prediabetic patients.


Fiber Supplementation for Metabolic Syndrome


A number of clinical studies suggest the usefulness of psyllium supplementation in addressing several components of the metabolic syndrome.  Psyllium improves lipid profile, reduces blood glucose and regulates insulin response.


How to Use


In some people, sudden and drastic increase in fiber can lead to side effects such as cramping, bloating and gas. This can be especially uncomfortable for people with IBS, as too much fiber can lead to worsening of their symptoms. Fiber supplementation should be done carefully, slowly and in small steps. It is best to start with only half a tablespoon (or less) of fiber daily. Increase the dose gradually until you either achieve a desired effect (regulation of bowel movement, relief in IBS symptoms, meal portion control, feeling of fullness) or until you meet a recommended amount of total fiber intake (supplements plus the fiber from food).


In clinical trials, the most commonly used dose of psyllium was 10g per day, divided into 2 or 3 portions. Psyllium was most often consumed either immediately before or during a meal.


Fiber is most effective in the presence of water. Psyllium (3-5g) should be taken with a full glass of water to ease the swallowing. In addition, water or some other suitable liquid should be drank throughout the day. Excellent water substitutes are various teas that also offer health benefits, such as green (offers antioxidant properties) peppermint, chamomile (can soothe abdominal discomfort), cinnamon (may lower blood glucose). 




The most common side effects of fiber supplementation are abdominal cramping, gas and bloating. Try lowering your dose to reduce discomfort.


Inhalation of psyllium powder may lead to allergic reactions in sensitive people and those with asthma. If you are using the powder, be careful when mixing it with water to avoid inhalation.


Just like it affects macronutrient absorption, psyllium can interfere with absorption of certain drugs. Some drugs the effectiveness of which might be diminished in interaction with psyllium include: lithium, digoxin, carbamazepine, and tricyclic antidepressants. Consult your doctor whether psyllium may be interacting with the drugs you are taking. As a general rule, take psyllium independently of any other drug, leaving 2-4 hour window in-between.


Taking psyllium concurrently with diabetic medications may pose a risk of hypoglycemia. Check your blood glucose levels regularly and adjust the dose if needed. 


Psyllium supplementation


Pure psyllium can be found in three forms:


Whole husks. Good for baking and cooking, but when mixed with liquids can form a clumpy, grainy texture that is not easy to consume.


  • ​Organic India Organic Whole Husk Psyllium

Powder. Has a finer texture than whole husks, more appealing when mixed with liquids. Powder can be easily incorporated in many recipes.

  • Viva Naturals Organic Psyllium Husk Powder

  • Starwest botanicals Organic Psyllium Husk Powder

Capsules. Easier to take, capsules are especially convenient if you need fiber on the go.

  • Viva Naturals Psyllium Husk

Last updated: October 23, 2017

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