The Science of Beta Glucans and Your Immune System

If you feel like you're "doing everything right" but still want stronger everyday immune support, you're not alone. Many adults are looking for natural ways to help their body stay resilient through busy seasons, travel, and stress.

One group of nutrients getting a lot of attention are beta glucans—special fibers found in medicinal mushrooms, oats, barley, and certain yeasts. Human studies suggest that specific beta glucans can help your immune system stay alert and balanced, especially when life gets demanding.[1–3,6]

This guide breaks down what beta glucans are, how they interact with your immune system, and what the research actually shows, in simple, clear language.

What Are Beta Glucans?

Beta glucans are naturally occurring fibers found in the cell walls of:

• Mushrooms (like shiitake, reishi, and cordyceps)
• Oats and barley
• Baker's yeast and some algae

What makes them special is their structure: long chains of glucose linked in ways your body doesn't fully break down. The most studied for immune support are β-(1,3/1,6) beta glucans, common in mushroom supplements and yeast.[4,5]

Because your body can't fully digest these fibers, they interact with the immune system instead of just acting like a simple carbohydrate.[4,5]

How Beta Glucans Talk to Your Immune System

1. They act like "training signals" for innate immunity

Your innate immune system is your first line of defense. It includes:

• Macrophages (big eater cells)
• Neutrophils
• Dendritic cells
• Natural killer (NK) cells

These cells carry special receptors—like Dectin-1 and complement receptor 3—that recognize beta glucans and respond to them.[4,5]

When beta glucans bind to these receptors, studies show they can help:

• Activate or "wake up" key immune cells
• Support healthy signaling between innate and adaptive immunity
• Help immune cells better recognize and respond to everyday challenges[4,5]

Think of beta glucans as practice drills for your immune system, helping it stay ready without overstimulating it.

2. They may support balanced inflammatory responses

A healthy immune response isn't just about being strong—it's about being balanced.

In a human trial where adults ate shiitake mushrooms every day for four weeks, researchers saw:[1]

• Increased activity of certain T cells and natural killer T cells
• Higher levels of secretory IgA (an antibody that helps guard mucosal surfaces)
• A reduction in C-reactive protein (CRP), a marker linked with systemic inflammation, suggesting a less inflammatory environment

Another clinical study on reishi beta glucan found that 12 weeks of supplementation in healthy adults supported:[2]

• Higher counts of T-lymphocytes (CD3+, CD4+, CD8+)
• Improved CD4/CD8 ratio
• Increased natural killer cell counts and activity

Together, these findings suggest that beta glucans from mushroom extracts may help support normal immune activity while also helping maintain inflammatory balance within a healthy range.[1,2]

What Human Studies Say About Beta Glucans and Immune Support

Below is a quick look at what's been seen in human studies so far. These are generally small and often short-term, but they give useful signals.

Shiitake mushrooms and everyday immunity

In a four-week randomized dietary trial, healthy young adults ate whole shiitake mushrooms daily.[1] Results showed:

• Increased proliferation and activation of γδ-T cells and natural killer T cells
• Increased secretory IgA (sIgA), which helps defend mucosal surfaces like the mouth and gut
• Lower CRP and a shift toward a less inflammatory cytokine profile

In summary, daily shiitake mushroom intake helped support multiple arms of immune function and appeared to do so in a way that was not overly inflammatory.[1]

Reishi beta glucan and immune cell balance

A randomized, double-blind, placebo-controlled trial in healthy adults looked at β-(1,3/1,6) glucan from Ganoderma lucidum (reishi mushroom) over 12 weeks.[2] The reishi beta glucan group showed:

• Higher counts of T cells and natural killer cells
• Improved CD4/CD8 ratio (a marker of immune balance)
• Higher serum IgA and natural killer cell activity

These changes support the idea that reishi beta glucan can help maintain a robust and balanced immune profile in healthy adults.[2]

Reishi and antioxidant markers

Another controlled human study with reishi (Lingzhi) evaluated various biomarkers, including antioxidant status and cardiovascular risk markers.[3] After four weeks:

• Urinary antioxidant capacity increased
• There were no signs of liver, kidney, or DNA toxicity

While effects on other biomarkers were modest, this study supports that reishi mushroom can be used safely in healthy adults at the tested dose and may support antioxidant defenses.[3]

Yeast beta glucan and mucosal immunity

In a trial with physically active adults, baker's yeast beta glucan given around a period of intense exercise:[6]

• Helped maintain or increase salivary IgA compared to placebo after strenuous cycling

Because salivary IgA plays a key role in mucosal defense in the mouth and upper airways, this suggests yeast beta glucan may help support front-line immune barriers under physical stress.[6]

Another clinical study using oat beta glucan in endurance athletes found no significant changes in immune markers or symptom reports between the beta glucan and placebo groups, highlighting that not all beta glucan trials show benefit, and effects may depend on source, dose, and population.[7]

Cordyceps and perceived energy during intense exercise

Although cordyceps mushrooms are often marketed for "energy," human data are still emerging.

In one trial, a Cordyceps militaris–containing mushroom blend taken for three weeks improved:[8]

• Maximal oxygen consumption (VO₂max)
• Time to exhaustion during high-intensity exercise

This suggests cordyceps-containing blends may help support exercise tolerance and perceived stamina, which can indirectly support overall wellness during demanding periods.[8]

How Mushroom Beta Glucans Differ from Other Sources

Not all beta glucans are the same. Their source and structure matter.[4,5]

Mushroom beta glucans

• Often β-(1,3/1,6) structure
• Found in the cell walls of reishi mushroom, shiitake mushroom, maitake, turkey tail, and other medicinal mushrooms
• Widely studied for immune signaling and modulation[1–5]

Cereal beta glucans (oats, barley)

• Typically β-(1,3/1,4) structure
• Best known for supporting healthy cholesterol and blood sugar already in the normal range, with mixed data on immune markers in humans[7,9]

Yeast beta glucans

• Often β-(1,3/1,6) structure similar to fungal beta glucans
• Studied in the context of exercise, stress, and mucosal immune markers like salivary IgA[6]

Because structure affects how immune receptors "see" these molecules, mushroom-derived beta glucans are usually the focus when people talk about mushroom immune support.[4,5]

The Gut–Immune Connection: Where Beta Glucans Go

After you swallow beta glucans, they don't simply disappear.

• Reviews suggest that beta glucans reach the small intestine, where parts of them are taken up by immune cells in gut-associated lymphoid tissue.[5]
• Macrophages can internalize beta glucan fragments and carry them to lymphoid organs, where other immune cells interact with them.[5]
• In the shiitake study, higher secretory IgA (sIgA) in saliva suggests that dietary mushrooms may influence mucosal immune defenses, possibly through gut-immune signaling.[1]

This is one reason mushroom supplements and whole culinary mushrooms are being studied not just as food, but as immunologically active fibers.

Choosing a Beta Glucan–Rich Mushroom Supplement

If you're considering a mushroom immune support product, here are science-aligned things to look for:

Named species and plant part

• Look for specific mushrooms like Ganoderma lucidum (reishi), Lentinula edodes (shiitake), or Cordyceps militaris, and whether it's fruiting body or mycelium.
• Many human trials use defined mushroom species and preparations.[1–3,8]

Standardized beta glucan content

• Some high-quality mushroom supplements list the percentage of beta glucans, not just "polysaccharides."
• This is important because not all polysaccharides are immune-active.

Third-party testing and purity

• Look for products tested for heavy metals, pesticides, and microbial contamination.
• Reishi and other mushrooms have been studied for safety at certain doses and generally show good tolerance in healthy adults.[2,3]

Realistic expectations

• Current human studies are small and often short-term.
• Results show changes in immune markers, not miracle cures.[1–3,6–8]
• Beta glucans should be seen as one piece of a larger lifestyle picture (sleep, stress, nutrition, movement).

How to Use Beta Glucans in Everyday Life

You can support your immune system with beta glucans in two main ways:

Food sources

• Include cooked shiitake, maitake, or oyster mushrooms in stir-fries, soups, and eggs.
• Choose oats or barley as regular whole-grain options.

Supplement forms

• Reishi, shiitake, turkey tail, and cordyceps mushroom capsules or powders can provide concentrated beta glucans from fungi.
• Yeast-derived beta glucan supplements may also support mucosal immune markers during physical or lifestyle stress.[6]

Always remember: supplements are meant to support overall wellness, not replace sleep, nutrient-dense food, or medical care.

Key Takeaways

• Beta glucans are immune-active fibers found in medicinal mushrooms, oats, barley, and yeast.
• The most studied beta glucans for immune support are β-(1,3/1,6) types from mushrooms and yeast.[4,5]
• Human trials with shiitake and reishi show changes in immune cell activity, mucosal antibodies, and markers tied to inflammatory balance in healthy adults.[1–3]
• Yeast beta glucans have been shown to help maintain salivary IgA after intense exercise, a marker linked with mucosal immune defense.[6]
• Not all studies show measurable benefit, and effects can depend on the source, dose, and population.[7]
• Food-based beta glucans plus carefully chosen mushroom supplements can be part of a broader strategy to support immune health alongside sleep, nutrition, movement, and stress management.

FAQ

1. Are beta glucans "proven" to boost immunity?

No. Human studies show that beta glucans can support or modulate immune markers—like T-cell activity, natural killer cell counts, and secretory IgA—in specific settings.[1,2,6] That's different from being "proven" to prevent or treat disease. They should be viewed as supportive, not as a stand-alone solution.

2. Are mushroom beta glucans better than oat beta glucans?

They are different, not simply better or worse.

• Mushroom beta glucans are usually studied for immune signaling and balance.[1–5]
• Oat and barley beta glucans are better known for supporting cardiometabolic markers and have mixed results in immune studies.[7,9]

If your main focus is immune support, mushroom-derived beta glucans are more directly supported by the current human and mechanistic data.[1–5]

3. Can I just eat mushrooms instead of taking a supplement?

Culinary mushrooms like shiitake absolutely contribute beta glucans and other beneficial compounds. In fact, one trial used whole dried shiitake as the intervention and saw meaningful changes in immune markers.[1]

Supplements may be helpful if you:

• Don't regularly eat mushrooms
• Want a standardized amount of beta glucans from specific medicinal mushroom species

Both food and supplements can play a role, depending on your diet and goals.

4. Are beta glucans safe for long-term use?

In the human trials above, beta glucans from shiitake, reishi, and yeast were generally well tolerated with no serious safety signals in healthy adults at the tested doses.[1–3,6,8] However, long-term data are still limited.

If you have an underlying medical condition, take medications, or are pregnant or breastfeeding, talk with your healthcare provider before starting any new supplement.

What to Do Next

If you're curious about adding beta-glucan–rich mushrooms into your routine:

• Start with food: add shiitake or other culinary mushrooms a few times per week.
• If you choose a mushroom supplement, look for:
  • Clearly labeled species (e.g., reishi mushroom (Ganoderma lucidum))
  • Standardized beta glucan content
  • Third-party testing for purity and potency
• Pair it with the basics that your immune system truly loves:
  • Consistent sleep
  • A nutrient-dense diet
  • Daily movement
  • Stress management habits you can actually stick with

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Always consult your healthcare provider before starting any new supplement, especially if you have a medical condition, are pregnant or nursing, or take prescription medications.

References

1. Dai, X., Stanilka, J. M., Rowe, C. A., Esteves, E. A., Nieves, C., Jr., Spaiser, S. J., Christman, M. C., Langkamp-Henken, B., & Percival, S. S. (2015). Consuming Lentinula edodes (shiitake) mushrooms daily improves human immunity: A randomized dietary intervention in healthy young adults. Journal of the American College of Nutrition, 34(6), 478–487.
2. Chen, S.-N., Nan, F.-H., Liu, M.-W., Yang, M.-F., Chang, Y.-C., & Chen, S. (2023). Evaluation of immune modulation by β-1,3;1,6 D-glucan derived from Ganoderma lucidum in healthy adult volunteers: A randomized controlled trial. Foods, 12(3), 659. 
3. Wachtel-Galor, S., Tomlinson, B., & Benzie, I. F. F. (2004). Ganoderma lucidum ("Lingzhi"), a Chinese medicinal mushroom: Biomarker responses in a controlled human supplementation study. British Journal of Nutrition, 91(2), 263–269. 
4. Goodridge, H. S., Wolf, A. J., & Underhill, D. M. (2009). Beta-glucan recognition by the innate immune system. Immunological Reviews, 230(1), 38–50. 
5. Chan, G. C.-F., Chan, W. K., & Sze, D. M.-Y. (2009). The effects of beta-glucan on human immune and cancer cells. Journal of Hematology & Oncology, 2, 25. 
6. McFarlin, B. K., Carpenter, K. C., Davidson, T., & McFarlin, M. A. (2013). Baker's yeast beta glucan supplementation increases salivary IgA and decreases cold/flu symptomatic days after intense exercise. Journal of Dietary Supplements, 10(3), 171–183. 
7. Nieman, D. C., Henson, D. A., McMahon, M., Wrieden, J. L., Davis, J. M., Murphy, E. A., Gross, S. J., McAnulty, L. S., & Dumke, C. L. (2008). Beta-glucan, immune function, and upper respiratory tract infections in athletes. Medicine & Science in Sports & Exercise, 40(8), 1463–1471. https://doi.org/10.1249/MSS.0b013e31817057c2 PubMed
8. Hirsch, K. R., Smith-Ryan, A. E., Roelofs, E. J., Trexler, E. T., & Mock, M. G. (2017). Cordyceps militaris improves tolerance to high-intensity exercise after acute and chronic supplementation. Journal of Dietary Supplements, 14(1), 42–53. 
9. Ahmed, H. G. M. D., Yang, L., Yang, X., Yang, J., Hussain, S., Shafiq, M. D., Akram, M. I., Sajad, M., & Zeng, Y. (2025). Beta-glucan in barley as a natural immunomodulator: Mechanisms and therapeutic potential. Molecular Biology Reports, 52(1), 1012.