Beta-Glucans in Algae: What the Immune Research Shows

Search for "beta glucan" and you will find oats, baker's yeast, mushrooms and, increasingly, algae. They are not interchangeable. Beta-glucan is a family of molecules, and the version in your oatmeal behaves differently from the one in a microalga called Euglena. The most direct human evidence for an algal beta-glucan comes from two randomized trials of Euglena gracilis, both reporting fewer cold-like symptom days than placebo. Chlorella has its own human immune trial, though it never claimed beta-glucan as the reason. Spirulina earns its reputation elsewhere. This guide sorts out which algae offer what, with the sample sizes, funding and limits of each study in plain view.

ENERGYbits® • Immune Nutrition

What beta-glucan is and why immune researchers care

Beta-glucans are polymers of glucose joined by beta linkages, mainly 1,3 and 1,4 bonds, and sometimes 1,6 branches. They occur in cereals, fungi, yeast, bacteria and some microalgae [4]. In the gut, they are classed as dietary fiber: the laboratory method used to measure total dietary fiber (AOAC 991.43) is the one the Euglena researchers used to quantify beta-glucan content in their product [1].

The immune interest comes from how some beta-glucans are recognized. Reviews describe receptors on immune cells, including Dectin-1, complement receptor 3 and Toll-like receptors, that bind beta-1,3-glucans and set off signaling and cytokine release [10][11]. That is the proposed mechanism. A mechanism is a reason to run trials, not proof that a supplement does anything in people, so the rest of this article is organized around what the human trials found.

If you want the broader picture of immune nutrition first, our posts on Does Chlorella Support Your Immune System?, Does Spirulina Boost Your Immune System? and Immune Support Nutrients With Evidence cover whole-food angles. This piece zooms in on one compound and one question: which algae actually bring it.

Four beta-glucans, four different molecules

"Beta-glucan" on a label tells you the chemical family, not the structure, source, dose or study. Structure matters because immune receptors respond to shape, and research on one source does not transfer to another.

Euglena: the algae with human beta-glucan trials

Euglena gracilis is a single-celled, freshwater microalga. It stores energy as paramylon, granules of linear beta-1,3-glucan, and a review of microalgal beta-glucans lists Euglena at 70 to 80 percent of its carbohydrate content, far above the other microalgae in the same table [4]. That is why almost all of the algal beta-glucan research you will find uses it.

The 2019 trial: a Euglena fermentate in active adults

Evans and colleagues, working with the ingredient maker Kemin, ran a 90-day randomized, double-blind, placebo-controlled trial in London, Ontario [1]. Thirty-four endurance-trained adults aged 21 to 65 took either one 367 mg capsule a day of a Euglena gracilis fermentate (more than 50 percent beta-1,3-glucan) or a placebo. The outcome was self-reported upper respiratory tract infection (URTI) symptoms on the WURSS-24 questionnaire.

• The primary outcome, the percentage of participants reporting URTI symptoms, did not differ significantly between groups [1].
• On secondary outcomes, the Euglena group reported fewer sick days (1.46 vs 4.79), fewer symptom days (5.46 vs 15.43), fewer episodes (2.62 vs 4.79) and lower global severity than placebo [1].
• Sick days, symptoms and global severity were also lower at 30 days, and safety measures stayed within normal ranges [1].

The 2025 trial: whole Euglena powder in 213 adults

A larger randomized, double-blind trial published in 2025 by Nakashima and colleagues gave 213 healthy Japanese adults (aged 21 to 82) either 1,000 mg of Euglena gracilis powder or a starch placebo in a capsule once daily for 8 weeks [2]. Participants kept symptom diaries.

• The primary outcome, cumulative days with cold-like symptoms, was lower with Euglena: 15.9 days versus 21.3 days with placebo (p = 0.032) [2].
• In weeks 5 to 8, symptom days and the severity of fatigue, nasal congestion, sore throat and muscle aches were lower in the Euglena group [2].
• No adverse reactions related to the capsules were reported [2].

One practical note for readers of an algae company's blog: ENERGYbits sells spirulina and chlorella, not Euglena, and these trials used different organisms and different products. We include them because they are the best human evidence on algal beta-glucan, and because an honest answer to the topic requires them.

Chlorella: a human immune trial and an open question

Chlorella has a human immune trial of its own, and it is worth stating what that evidence is and is not.

What the trial found

In an 8-week randomized, double-blind, placebo-controlled trial in Korea, Kwak and colleagues gave healthy adults 5 g a day of Chlorella vulgaris tablets (23 participants analyzed) or placebo (28 analyzed) [3]. After 8 weeks the chlorella group showed a significant rise in serum interferon-gamma and interleukin-1 beta, a trend toward higher interleukin-12, and increased natural killer (NK) cell activity, with larger increases than placebo [3]. The authors suggest a beneficial immunostimulatory effect of short-term chlorella supplementation in healthy people.

The beta-glucan question

Here is where an honest article has to disagree with some of the internet. Online, chlorella is often described as a beta-1,3-glucan source. The Kwak trial does not mention glucan as the active component [3]. A 2025 review of microalgal beta-glucans lists the glucan reported in Chlorella pyrenoidosa as a cyclic beta-1,2 type, present at under 5 percent, and discusses it in a bacterial-symbiosis context rather than an immune one [4]. That is a different molecule from the linear beta-1,3 paramylon in Euglena.

That does not make chlorella irrelevant to immune research. Laboratory work on polysaccharides isolated from chlorella is active: a 2025 study of a purified Chlorella pyrenoidosa polysaccharide (CPP-3a) reported that it activated macrophages in cell culture through TLR4 and TLR2 signaling [9]. That is a cell-culture result, an interesting lead and not a human outcome. So the fair summary is this: whole chlorella has a human trial with positive immune markers; chlorella polysaccharides are being studied in the lab; and no human trial we found shows that chlorella works through beta-1,3-glucan.

What chlorella does bring to the table is nutritional: chlorophyll, protein and micronutrients in a whole food, and in ENERGYbits chlorella, a cracked cell wall for digestibility. For more on that angle, see our guide to Does Chlorella Support Your Immune System?.

Where spirulina fits

Spirulina is a cyanobacterium, not a eukaryotic alga, and the reviews of algal beta-glucan that we read name Euglena and several other microalgae but not spirulina [4]. The nutrition data point the same way: USDA FoodData Central lists dried spirulina at about 3.6 g of dietary fiber per 100 g [8]. By calculation, an ENERGYbits full serving of 7.5 g (30 x 250 mg tablets) supplies roughly 0.27 g of total fiber, and beta-glucan, if any, could only be a fraction of that.

This is not a knock on spirulina. It is a reason to ask what spirulina is for. Its nutritional case rests on protein, phycocyanin, chlorophyll, vitamins and minerals, and its immune research focuses on other components such as phycocyanin and polysaccharide fractions studied in the laboratory. If you came here asking whether spirulina is a beta-glucan supplement, the answer is no. If you are asking whether it belongs in an immune-minded diet, our dedicated guide, Does Spirulina Boost Your Immune System?, walks through that evidence on its own terms.

Yeast and oat: useful context

Oat and barley

The strongest regulatory-grade finding for any beta-glucan is for oats and barley, and it concerns cholesterol rather than immunity. EFSA's panel concluded in 2010 that a cause-and-effect relationship exists between oat beta-glucan intake and lower blood LDL cholesterol, with a daily intake of at least 3 g of beta-glucan for the claim [7]. Cereal beta-glucan is soluble, viscous fiber; it is a different tool from the particulate, immune-oriented beta-glucans in yeast and Euglena.

Baker's yeast

Yeast beta-1,3/1,6-glucan has a growing set of small randomized trials on upper respiratory outcomes. A 2026 trial in Japan randomized 40 healthy adults to a yeast glucan or placebo for 12 weeks; the yeast group reported fewer days with upper respiratory symptoms, and mucosal immune markers such as secretory IgA were better preserved [5]. The authors call these preliminary observations. A 12-week trial of 198 moderately stressed adults reported lower respiratory symptom scores at 120 mg and 204 mg a day than placebo, with only the 204 mg dose exceeding the minimal clinically important difference [6]. Yeast evidence is more developed than algal evidence, though its own authors still call it early.

How to read supplement trials like these

Headlines love the verb "boosts." A few habits help you read past it.

• Check the outcome. Immune markers such as NK cell activity or cytokines show that something changed in blood tests. Symptom days show what people felt. Neither is the same as fewer infections.
• Check which outcome was primary. The 2019 Euglena trial missed its primary outcome and reported benefits on secondary measures; the 2025 trial met its primary outcome [1][2].
• Check who paid. All of the algal trials discussed here involved the product maker. That does not invalidate them, and independent replication would still strengthen them considerably.
• Match the product. A trial of a Euglena fermentate at 367 mg says nothing about what a chlorella tablet does, and vice versa.
• Respect the cell-culture line. Macrophage results explain mechanisms. They are not human findings.

A food-first immune routine

Whatever you decide about supplements, the evidence for the basics is stronger than for any single compound. Our Immune Support Nutrients With Evidence article walks through vitamin D, zinc, vitamin C and food sources in detail. In brief:

• Eat enough, and eat varied. Immune cells need protein, zinc, iron, selenium, vitamins A, C, D and E, among others. Diet quality matters more than any one input.
• Include oats and barley. They are the best-studied food sources of beta-glucan, and EFSA's cholesterol finding applies to them [7].
• Protect sleep and manage stress. Both shape immune function, and the yeast beta-glucan trial that enrolled moderately stressed adults is a reminder that stress is part of the picture [6].
• Stay current on vaccinations and routine care. No supplement substitutes for them.

Precautions, calmly

Beta-glucans are studied precisely because they interact with the immune system, so a short precautions note belongs here. Spirulina and chlorella are generally well tolerated. Check with your healthcare provider before taking them if you are pregnant or nursing, have phenylketonuria, have an autoimmune condition, take immunosuppressant medication or blood thinners, have a bleeding disorder, or have thyroid or iodine concerns (relevant to chlorella). People managing autoimmune conditions or taking immunosuppressants in particular should talk to their clinician before adding any product marketed for immune support, algal or otherwise. ENERGYbits products are third-party tested for purity and contaminants.

If you add algae to your routine

Many people ease into a new whole-food supplement gradually. That is common practice, not a clinical recommendation. ENERGYbits tablets are 250 mg each, and a full serving is 30 tablets (7.5 g). Both spirulina and chlorella are single-ingredient whole foods with no fillers or additives, freshwater-grown, gently dried at low temperatures and third-party tested for purity and contaminants.

If you are curious about spirulina for its protein, phycocyanin and chlorophyll, start with the ENERGYbits spirulina. If you would like both algae together, the VITALITYbits spirulina and chlorella blend combines them. Neither is a beta-glucan product and neither is sold to treat or prevent any condition. They are whole-food nutrition.

Conclusion

Beta-glucan is a legitimate and interesting area of immune nutrition, and algae have a real place in it, specifically Euglena gracilis, which has two randomized trials behind its paramylon story. The honest edges are equally clear: small, industry-funded, symptom-based studies that call for independent replication.

For the algae ENERGYbits grows, the picture is different but still positive. Chlorella has a human trial with encouraging immune markers, and spirulina brings protein, phycocyanin, chlorophyll and minerals. Neither needs to be a beta-glucan source to earn a place in a whole-food routine.

Frequently asked questions

What is beta-glucan? +

Beta-glucan is a family of glucose polymers with beta linkages, found in oats, barley, yeast, mushrooms, bacteria and some microalgae. Structure varies by source, which affects how the body responds [4]. Cereal beta-glucan is soluble fiber studied for cholesterol; yeast and Euglena beta-glucans are studied for immune outcomes.

Which algae contain beta-glucan? +

Euglena gracilis is the best-documented, with a linear beta-1,3-glucan (paramylon) at 70 to 80 percent of its carbohydrate content [4]. Other microalgae contain smaller amounts of various types. Spirulina is not named as a beta-glucan source in the reviews we read, and the glucan reported in Chlorella pyrenoidosa is a cyclic beta-1,2 type at under 5 percent [4].

Does spirulina contain beta-glucan? +

Spirulina is a cyanobacterium and is not described as a notable beta-glucan source in algal reviews [4]. Dried spirulina has about 3.6 g of total fiber per 100 g, so a 7.5 g serving provides about 0.27 g (calculation) [8]. It is valued for protein, phycocyanin, chlorophyll, vitamins and minerals instead.

Does chlorella contain beta-1,3-glucan? +

Evidence for the linear beta-1,3 type is lacking. One 2025 review lists the glucan reported in Chlorella pyrenoidosa as a cyclic beta-1,2 type at under 5 percent [4]. Chlorella contains other polysaccharides studied in the laboratory [9]. A human trial of whole chlorella reported higher NK cell activity without attributing it to beta-glucan [3].

What is paramylon? +

Paramylon is the storage carbohydrate of Euglena gracilis, a linear beta-1,3-glucan that makes up most of the cell's carbohydrate content [4]. Randomized trials of Euglena products, whose beta-glucan is paramylon, reported fewer days of cold-like symptoms than placebo, though the authors note the mechanism was not directly measured [1][2].

Does Euglena beta-glucan help with colds? +

Two randomized, placebo-controlled trials reported fewer days with cold-like symptoms on Euglena products: 213 adults taking 1,000 mg of powder for 8 weeks [2], and 34 active adults taking a 367 mg fermentate for 90 days, where the primary outcome was not met but secondary measures favored Euglena [1]. Both were industry-funded and relied on self-reports.

Did the chlorella immune trial show fewer infections? +

No. The 8-week trial of 5 g a day of chlorella measured immune markers, finding higher NK cell activity, interferon-gamma and interleukin-1 beta than placebo [3]. It did not measure infections or symptoms, and it was a small study partly funded by the manufacturer.

Is yeast beta-glucan better than algae beta-glucan? +

It is better studied. Small to moderate randomized trials of yeast beta-1,3/1,6-glucan report fewer upper respiratory symptoms or better mucosal immune markers [5][6], while algal beta-glucan evidence is mostly two Euglena trials. The molecules differ, so results do not transfer between them, and the authors of each describe their findings as early.

Does oat beta-glucan support immunity? +

Its best-supported benefit is cholesterol. EFSA concluded that oat beta-glucan at 3 g or more per day lowers blood LDL cholesterol [7]. Oat beta-glucan is a soluble fiber and is not the same as the particulate beta-glucans studied for immune outcomes.

What does a "beta-glucan supplement" label actually tell me? +

Very little by itself. It does not tell you the source, structure, amount or whether the dose matches a trial. Look for the organism, the milligrams of beta-glucan and the studies on that exact product, and keep in mind that results from one source do not carry over to another.

Who should check with a doctor before using beta-glucan or algae products? +

People who are pregnant or nursing, who have phenylketonuria, an autoimmune condition, a bleeding disorder, or thyroid or iodine concerns, or who take immunosuppressants or blood thinners should consult their healthcare provider first. This applies to immune-support products in general.

How many ENERGYbits tablets are a serving? +

A full serving is 30 tablets, each 250 mg, for 7.5 g in total. The chlorella immune trial used 5 g a day of a different product, which is not a dose recommendation [3].

This article is for educational purposes only and is not medical advice. These statements have not been evaluated by the FDA. ENERGYbits® products are whole-food supplements and are not intended to diagnose, treat, cure, or prevent any disease. Talk with your doctor before starting any supplement, especially if you are pregnant, nursing, taking medication, or managing a medical condition.

References

1. Evans M, Falcone PH, Crowley DC, et al. Effect of a Euglena gracilis Fermentate on Immune Function in Healthy, Active Adults: A Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients. 2019;11(12):2926. https://doi.org/10.3390/nu11122926
2. Nakashima A, Suzuki K, Nagata M, Takara T. Euglena gracilis Suppresses Cold Symptoms in Healthy Individuals: A Double-Blind, Randomized, Placebo-Controlled Trial. Food Sci Nutr. 2025. https://doi.org/10.1002/fsn3.70935
3. Kwak JH, Baek SH, Woo Y, et al. Beneficial immunostimulatory effect of short-term Chlorella supplementation: enhancement of natural killer cell activity and early inflammatory response (randomized, double-blinded, placebo-controlled trial). Nutr J. 2012;11:53. https://doi.org/10.1186/1475-2891-11-53
4. Li C, Du M, Han Y, et al. Microalgae in health care and functional foods: beta-glucan applications, innovations in drug delivery and synthetic biology. Front Pharmacol. 2025. https://doi.org/10.3389/fphar.2025.1557298
5. Kanno T, Ishibashi KI, Kajiyama S, et al. Dietary beta-1,3/1,6-Glucan from Baker's Yeast Supports Upper Respiratory Mucosal Immune Health in Healthy Adults: Evidence from a Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients. 2026;18(6):961. https://doi.org/10.3390/nu18060961
6. Habibullah NNM, Ismail M, Ibrahim N, et al. Low-dose of yeast beta-glucan on respiratory symptoms and psychological well-being in moderately stressed adults. iScience. 2026. https://doi.org/10.1016/j.isci.2026.115120
7. EFSA Panel on Dietetic Products, Nutrition and Allergies. Oat beta glucan and lowering blood cholesterol. EFSA Journal. 2010;8(12):1885. https://www.efsa.europa.eu/en/efsajournal/pub/1885
8. U.S. Department of Agriculture, FoodData Central. Seaweed, spirulina, dried (FDC ID 170495, SR Legacy). https://fdc.nal.usda.gov/food-details/170495/nutrients
9. Pi Y, Yuan Q, Qin S, et al. Chlorella pyrenoidosa Polysaccharide CPP-3a Promotes M1 Polarization of Macrophages via TLR4/2-MyD88-NF-kB/p38 MAPK Signaling Pathways. Mar Drugs. 2025;23(7):290. https://doi.org/10.3390/md23070290
10. Wang W, Wang J, Wu N, et al. Algal beta-glucan: Structure, immunomodulatory effects and application prospects. Carbohydr Polym. 2026. https://doi.org/10.1016/j.carbpol.2025.124801
11. Samiksha F, Singh D, Harbool SS, et al. Fungal beta-1,3-glucans: Cell Wall Constituents That Promote Gut Health Through Innate Immune Modulation. Nutrients. 2026;18(11):1794. https://doi.org/10.3390/nu18111794