Life Extension Magazine®

Example of intestine that is benefited by fiber for immune function

Bridging the Fiber Gap

With almost 70% of the immune system located in the gut, it should not be surprising that intestinal fiber fermentation is involved in immune health. Research has shown that three forms of fiber provide broad-spectrum benefits including protecting against the effects of metabolic syndrome, while improving digestion and immune function.

Scientifically reviewed by: Dr. Shanti Albani, ND, Physician, in August 2023. Written by: Leslie Stanton.

Over 2,000 years ago, Hippocrates said that all disease begins in the gut.

Modern science is proving how right he was.

Scientists are discovering that fiber not only boosts digestive health but also contributes to our immune function.1 This makes sense, considering 70% to 80% of the cells of the immune system are located in the gastrointestinal tract.2

Studies show that dietary fiber has multiple properties that improve cardiovascular and metabolic biomarkers—and even extend life span.

Despite its importance, few Americans get the recommended intake of fiber per day through diet alone, making what is called the “fiber gap” a public health concern.

To help fill this dietary “gap,” researchers have created a broad-spectrum formula by combining three different fibers that offer immune support and improved intestinal health.

The primary component is a unique fiber called beta-glucan. Derived from baker’s yeast, beta-glucans are essential for boosting the intestine’s immune system function. Beta-glucans have a unique molecular structure that captures the attention of cells in the immune system of the intestine.3-5

When beta-glucans are blended with two other fiber sources, psyllium and fruit from the African Baobab tree, the combination offers powerful immune metabolic, and intestinal support.

Beta-Glucans Revive Exhausted Immune Systems

Beta-glucans are crucial weapons in the fight for health and longevity. These molecules naturally boost the immune system by optimizing its response to diseases and infection.6

While beta-glucans can be obtained from sources such as shiitake mushrooms and cereal grains, beta-glucans that come specifically from baker’s yeast have a unique molecular structure that grabs the attention of cells in the immune system of the intestine.3-5

Beta-glucans “prime” the immune system to be ready to respond to threats throughout the entire body. Such priming helps increase the immune system’s responsiveness to foreign molecules, such as those found on bacteria and viruses. In addition, it can assist in the fight against cancer by enhancing the immune system’s ability to detect and destroy malignant cells.6

Beta-glucans have numerous actions that help supercharge the immune system:

  • Beta-glucans promote the emergence of T cells,7 which are white blood cells that help the body fight diseases or harmful substances.
  • Beta-glucans have been shown to increase the body’s antitumor immune response, while decreasing immune-suppressive cells that cancer cells use as protection against immune detection and destruction.3
  • Beta-glucans promote the production of interferon-gamma, a powerful antiviral and immune-modulating signaling protein with specific actions against many viruses that cause human disease.8
  • Finally, beta-glucans from baker’s yeast have been found to increase the salivary levels of immunoglobulin A (IgA) antibodies. Immunoglobulin A antibodies are the first line of defense against cold and flu viruses and may help prevent worsening of symptoms.9

All of these immune-boosting benefits seen at the cellular level have been shown to have real-world effects. Human studies demonstrate how beta-glucan supplementation can rejuvenate the immune systems of those who need it most.

Human Studies

Human Studies 

Marathon runners are especially good subjects for the study of immune-boosting supplements because they are particularly susceptible to developing upper respiratory tract infections (colds) after a run.9,10

Beta-glucans have been found to reduce the severity and duration of cold symptoms in marathon runners, demonstrating their ability to activate immune cells.

In one study, a daily dose of 250 or 500 mg of beta-glucans was found to reduce reports of upper respiratory tract infections in the four weeks following a marathon.11 That improvement was also associated with better overall health and decreased confusion, fatigue, tension, and anger, as well as increased vigor, based on a standard profile of mood state survey.

A subsequent study showed that marathon athletes who supplemented with beta-glucans demonstrated a significant 37% reduction in the number of days they presented with cold or flu symptoms in the 28-day period following a marathon, compared with placebo recipients. Levels of salivary antibodies (immunoglobulin A) were also increased by 32% at two hours following exercise, compared with placebo recipients.9

Any form of strenuous exercise temporarily weakens the immune system.12 For the next study, recreationally active men and women supplemented with 250 mg per day of beta-glucans. After 10 days, the subjects experienced significant increases in microbe-destroying white blood cells and signaling molecules that promote immune system detection and destruction of viruses and bacteria.12

The likely explanation for the reduction in cold or flu symptoms seen in such subjects is that immunoglobulin A is vital in preventing viruses from attaching to the mucous membranes of the mouth, nose, and throat.13

What You Need to Know
Fiber Trio Provides Critical Immune Support

Fiber Trio Provides Critical Immune Support

  • Americans suffer from a “fiber gap,” consuming only one-half to two-thirds of the recommended daily amount of dietary fiber.
  • This fiber gap contributes not only to suboptimal intestinal health but also to a growing vulnerability to systemic disorders such as cardiovascular and metabolic diseases, as well as inadequate immune function.
  • Researchers have identified three forms of fiber that support both immune and intestinal health.
  • Beta-glucans from baker’s yeast powerfully boost immune function in the intestine, causing effects throughout the whole body.
  • Beta-glucans reduce the severity and duration of cold symptoms in stressed humans by activating immune cells through specific molecular mechanisms.
  • Psyllium fiber and Baobab fruit powder have proven abilities to release the vital short-chain fatty acids the body needs for optimum immune, cardiovascular, and metabolic function.
  • Using these three sources of fiber together can help close the fiber gap in order to ensure total body health.

Beta-Glucans Battle the Impacts of Stress

Stress also lowers the immune system’s resistance to cold symptoms. Beta-glucans from baker’s yeast, dosed at 250 or 500 mg per day for four weeks, reduced such symptoms. Again, these benefits were accompanied by an improvement in overall health and vigor and a reduction in tension, fatigue, and confusion, based on the profile of mood states standard survey.14

In a group of healthy women with moderate psychological stress, just 12 weeks of supplementation with 250 mg of beta-glucans per day significantly reduced upper respiratory symptoms by 66% compared to placebo. Additionally, the women taking beta-glucans experienced a boost in overall well-being scores by more than 8% and mental/physical energy levels by 21%.15

Another group of people known to be under a tremendous amount of stress are university students. A study published in Nutrition analyzed healthy university students at the peak of the cold season for 90 days. In students who developed symptoms during this time, the ones taking 250 mg per day of beta-glucans showed a clinically relevant reduction in the total number of days with symptoms compared with placebo recipients. The supplemented students also had a statistically significant increase in the ability to “breathe easily.”16

Protection against an Overactive Immune Response

Allergies are at the other end of the spectrum of immune system disturbances. They are characterized by an overactive immune response to foreign matter. Evidence of the comprehensive immune modulating effect of beta-glucans comes from a study of ragweed allergy sufferers who are otherwise healthy.17

At the beginning of the fall ragweed season, subjects began supplementation with either beta-glucan or a placebo for four weeks. Supplementation resulted in significant reductions of 28% in total allergy symptoms, 52% in symptom severity, and 37% in symptom rating on a visual scale.17

On the profile of mood states scale, supplemented subjects reported significant increases in vigor of 10%, as well as reductions in tension (34%), depression (45%), anger (41%), fatigue (38%), and confusion (34%). And on a health survey used in a variety of studies, beta-glucan recipients scored a significant 11% higher on physical health, 19% higher on energy, and 7% higher on emotional well-being, compared with placebo recipients.17

Finally, the beta-glucan group reported significant reductions in allergy-related sleep problems (53%), nasal symptoms (59%), eye symptoms (57%), and non-nasal symptoms (50%), as well as improvements in activities (53%), emotions (57%), quality of life (56%), and improved global mood state (13%).17

An array of research has shown the beneficial effects on the immune system in those that supplement with beta-glucans derived from baker’s yeast. Fiber supplementation with psyllium and Baobab fruit offers an added layer of immune and health-boosting properties as we are about to learn.

Soluble/Insoluble Fiber Types
Soluble/Insoluble Fiber Types

Dietary fiber comes in two main categories, soluble and insoluble fiber. Soluble fiber, as the name implies, can dissolve in water. It is the chief source of fermentable fiber that is digested in the colon to produce vital short-chain fatty acids.

Insoluble fiber cannot dissolve in water, and its chief function is to provide bulk to fecal matter. The combination of beta-glucans, psyllium, and fruit from the Baobab tree provide fiber in a ratio of approximately 75% or more soluble fiber to about 25% insoluble fiber.

Why Is Fiber So Important?

The secret to fiber’s dramatic impact on the immune system isn’t the fiber itself but what happens to it once it enters the body. Since fiber cannot be broken down by human digestive enzymes, it passes unchanged through the upper parts of our digestive tract. That undigested fiber is then fermented by beneficial bacteria living in part of the large bowel known as the colon.18

Fermentation itself has many benefits, including supporting beneficial gut bacteria. However, it is the breakdown products of the fermentation process that are now recognized as holding the key to improved digestive and total body health.18,19

Those byproducts are primarily short-chain fatty acids, specifically acetate, propionate, and butyrate, which nourish and protect the cells lining the colon wall.18-21

In addition to serving as beneficial nutrients for cells that line the intestines, recent studies demonstrate that the short-chain fatty acids produced from soluble fiber are crucial for normal immune function.19,20 These are a few of their most potent immune-boosting mechanisms of action:

  • They regulate the activity of intestinal white blood cells, modulating their inflammatory responses to potential invaders such as disease-causing bacteria and viruses.20
  • They help those white cells produce the chemical signals (cytokines, prostaglandins, and interferons) that direct other immune system cells to sites of infection where they destroy dangerous microbes.20
  • They promote the development of regulatory T cells that either increase or decrease the immune response, depending on the nature of the microbe.22,23

It has recently been shown that the effects of these fiber-derived short-chain fatty acids go even further, powerfully modifying the expression of genes involved in immune function and longevity.20

Fiber and Metabolic Syndrome

Fiber and Metabolic Syndrome 

In addition to boosting the immune system through the creation of short-chain fatty acids, fiber also promotes good health by fighting against metabolic syndrome (the combination of abdominal obesity, high blood pressure, blood lipid disturbances, and loss of blood sugar control). Metabolic syndrome underlies multiple age-related disorders, promoting diabetes, cardiovascular disease, cancer, major depression, and even osteoporosis, among other preventable conditions.24-26 Sufficient fiber in the diet is turning out to be essential in the fight against all of these conditions.

As early as 1981, there was evidence that improving fiber intake could help manage blood sugar levels in type II diabetics.27

Numerous studies have since confirmed that soluble fibers can lead to reductions in fasting and after-meal blood sugar, as well as beneficial reductions in insulin levels (high insulin is associated with cancer promotion). A reduction in blood cholesterol, triglycerides, and blood pressure was also found.28-38 Other research demonstrates fiber-induced reductions in the response of appetite-promoting hormones, which may help to produce a sense of fullness and prevent overeating.39

Two fibers, psyllium and Baobab fruit, have been found to have specific benefits against metabolic syndrome. In addition, psyllium is rich in soluble fiber, which ferments the short-chain fatty acids that are so critical to maintaining a strong immune system. Let’s look at each one of these fibers.

Psyllium Fiber

Psyllium is the fiber obtained from the seed husks of a plantain (unrelated to the edible plantains found in many markets). When compared to the fiber in wheat bran, psyllium leads to greater production of beneficial short-chain fatty acids (specifically butyrate, propionate, and acetate) throughout the colon, perhaps because it is more rapidly fermented by colonic bacteria.40

Butyrate has vital anti-inflammatory properties.41,42 In an experimental rat model of ulcerative colitis (an inflammatory bowel disease), psyllium fiber supplementation reduced colonic inflammation, while decreasing the concentrations of important pro-inflammatory signaling molecules, such as leukotriene B4 and tumor necrosis factor alpha.42

While perhaps most known for its ability to combat constipation, recent human studies have revealed that psyllium is a proven weapon in the fight against metabolic syndrome and its devastating consequences.37 When used regularly, psyllium has been shown to beneficially impact cholesterol, blood sugar, and digestive health.


Studies have shown that increased psyllium fiber intake translated into reductions in plasma triglycerides and low-density (“bad”) cholesterol.37,43,44 In a study involving type II diabetics, 12-week supplementation with 15 grams of psyllium daily significantly reduced plasma triglycerides by 25.5%, total cholesterol by 9.3%, and LDL cholesterol by 15.71%, while significantly raising levels of high-density (“good”) cholesterol in comparison to the placebo group.37

Smaller doses show benefits as well, with a 6-gram per day dose of psyllium leading to a 6% reduction in LDL cholesterol.32

Blood Sugar

On the blood sugar front, a daily dose of 15 grams (three 5-gram doses) produced a reduction in fasting blood glucose levels in patients with type II diabetes.37 Another study found reductions in all-day glucose levels (11%) and after-lunch glucose levels (19%) among psyllium recipients, compared with placebo.45

A similar dose of psyllium, 14 grams per day, reduced glucose absorption from a meal by more than 12%, contributing to a reduction in blood sugar.44

In type II diabetics specifically, two months of psyllium treatment effectively optimized metabolic control, significantly reducing body mass index, waist circumference, hemoglobin A1c (a measure of long-term glucose control), and fasting blood sugar levels.43

Digestive Health

Psyllium is best known for its ability to combat constipation. The seed husks swell greatly in water, which aids patients with constipation by providing bulk and retaining water in stools. Animal studies show that psyllium fiber increases fecal weight and water content more effectively than twice the dose of wheat bran fiber, while also increasing the water content of feces.40

And human studies have demonstrated psyllium fiber’s ability to reduce fecal incontinence by more than 50% compared with placebo, while increasing fecal water-holding capacity.46-48 In addition, it has been shown to effectively lower symptom severity in patients with irritable bowel syndrome (IBS) significantly better than placebo or bran.49

Fiber: A Matter of Life and Death

Fiber has long been viewed simply as a way to support regular, normal bowel movements (i.e., to overcome constipation).55 However, recent studies show a strong association between insufficient dietary fiber intake and the risk of dying from any cause. A large meta-analysis with nearly a million subjects showed that, compared with people with the lowest one-third of fiber intake, those in the highest third had a 16% reduction in the risk of death. Each 10-gram per day increase in fiber led to an additional 10% reduction in the risk of death.56

And a study conducted by the National Institutes of Health (NIH) and the American Association of Retired Persons (AARP) revealed that, compared with the lowest one-fifth, those with the highest one-fifth of fiber intake had a 22% reduction in the risk of dying from any cause.57 This study also showed reductions in the risk of dying from cardiovascular disease, infections, and respiratory diseases of 34% to 59% in women and 24% to 56% in men.

The United States Department of Agriculture (USDA) recommends daily fiber intakes of 28 grams per day for men over 50 and 22 grams per day for women in that age group.58 However, the average American’s fiber intake is a meager 16 grams per day, a shortfall of 43% for men and 27% for women.59

The problem is that it is difficult to get the recommended amounts of fiber purely from food. And, while many people believe that whole-grain foods and nuts are a good fiber source, few such foods in fact supply the recommended 3 grams or more per serving of fiber. 55

Because of the health benefits that dietary fiber has on human health, this “fiber gap” has been identified as a major public health concern.55

In response to the fiber gap that is so pervasive in the American diet, scientists have formulated a fiber combination aimed at closing that gap, a combination that includes beta-glucans, psyllium, and Baobab fruit.

This unique combination of fibers provides 6 grams of fiber per serving. The recommended daily fiber intake for men and women are 28 and 22 grams per day, respectively.58 Given the average American’s daily fiber intake of 16 grams, one serving for women and two servings for men would bring total fiber consumption up to the daily recommendation by the USDA for men and women over 50.

Increasing fiber intake to and above recommended values can provide many health benefits, including reductions in risks for metabolic syndrome, cardiovascular disease, diabetes, cancer, and more.

Baobab Fruit Powder: Unique and Novel Source of Fiber

Unique and Novel Source of Fiber  

The powdered, dried fruit of the Baobab tree completes this protective fiber trio. Like psyllium, it has the ability to promote gut health while also defending against metabolic syndrome.

Baobab fruit has a long history of health-promoting effects on the gastrointestinal tract, particularly in the treatment of infantile diarrhea.50 But Baobab fruit pulp may also have unique prebiotic properties. This was demonstrated by a study showing that a 4% solution of the fruit pulp promoted growth of the probiotic Lactobacillus rhamnosus, an organism important in human intestinal health.51

Baobab fruit can also help defend against metabolic syndrome and diabetes by slowing the rate of digestion of carbohydrates. In a human study, dried Baobab fruit powder reduced the amount of rapidly digestible starch from white bread samples, an effect that lowered the resulting blood sugar response when people consumed the bread.52 This reduction in glycemic response is an important approach to lowering the damaging effects of blood sugar elevations, particularly following meals.53,54


While many people continue to think of dietary fiber as an aid to intestinal function only (e.g., preventing constipation), in reality fiber has taken on tremendous importance for supporting a healthy immune system and the health of the entire body.

Fiber molecules are fermented in the colon to produce valuable short-chain fatty acids that affect health in numerous ways—from preventing colon cancer and boosting immune function to modifying the metabolism to better cope when fats and sugars consumed.

A combination of three forms of fiber offers both immune and intestinal health support.

Beta-glucans “prime” the immune system, increasing its responsiveness to foreign molecules such as those found on bacteria and viruses, while enhancing its ability to detect and destroy malignant cells.

Psyllium fiber is a rich source of soluble fiber that produces beneficial short-chain fatty acids. It is a proven weapon in the fight against metabolic syndrome and its devastating consequences.

The powdered, dried fruit of the Baobab tree completes this protective trio, offering a boost to beneficial gut bacteria and slowing the surge of glucose into the bloodstream that occurs after a carbohydrate meal, helping to further defend against metabolic syndrome and diabetes.

Without ample fiber intake, people risk more than constipation. Rather, they place themselves in unnecessary peril of serious but preventable immune, cardiovascular, and metabolic disorders. Using these three sources of fiber together can help close the fiber gap in order to ensure total body health.

If you have any questions on the scientific content of this article, please call a Life Extension® Health Advisor at 1-866-864-3027.

Editor's Note

Science continues to evolve, and new research is published daily. As such, we have a more recent article on this topic: Phages Improve Intestinal and Immune Health


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