If you want to maintain an active and vibrant lifestyle as you age, immune health is an important consideration. Starting with the traditional food cultures of regions known for their seaweed consumption, we explore Fucoidan found in brown seaweed and what animal studies have revealed about its potential biological effects.

This article covers three topics: (1) researchers’ interest in seaweed-rich diets and regions known for longevity, (2) age-related changes in immune function, and (3) scientific findings on Fucoidan.

01. Okinawa and Jeju: Seaweed as Part of Traditional Diets

Okinawa, Japan is frequently recognized as a region associated with longevity. Seaweed varieties such as Wakame, Kombu, and Mozuku have long been part of its traditional cuisine. In particular, Okinawa Prefecture reportedly accounts for more than 90% of Japan’s domestic supply of Okinawan Mozuku (Cladosiphon okamuranus).

On Jeju Island in South Korea, female divers known as Haenyeo have harvested seaweed, including hijiki, from coastal waters for generations. Jeju’s Haenyeo culture was inscribed on UNESCO’s Representative List of the Intangible Cultural Heritage of Humanity in 2016. In 2023, the Food and Agriculture Organization of the United Nations (FAO) designated the Jeju Haenyeo Fisheries System as a Globally Important Agricultural Heritage System (GIAHS).

According to the FAO, Jeju’s coastal waters are home to 522 species of seaweed, representing approximately 70% of all seaweed species found in South Korea.

So, what might be the relationship between traditional seaweed consumption and healthy aging?

A scientific literature review by Murai and colleagues (2021) discussed the possibility that seaweed consumption may have contributed to longevity in Japan. Although longevity cannot be attributed to seaweed alone, researchers have investigated various bioactive compounds found in seaweed. Among these, Fucoidan, a naturally occurring component of brown seaweed, has attracted scientific interest.

02. Why Immune Health Matters More as We Age

As we grow older, our immune system naturally undergoes changes. This process is known as immunosenescence, or age-related immune aging. These changes may contribute to reduced responses to vaccines or slower recovery from common infections, such as colds.

The foundation of immune health, however, begins with everyday lifestyle habits. Getting adequate sleep, exercising regularly, maintaining a balanced diet, and staying up to date with vaccinations recommended by the Centers for Disease Control and Prevention (CDC) should remain priorities. Including traditional foods such as seaweed as part of a balanced diet may also be one way to support overall nutritional well-being.

03. Brown Seaweed and Fucoidan

Fucoidan is a sulfated polysaccharide naturally found in various species of brown seaweed, including Mozuku, Mekabu (the sporophyll of wakame), Bladderwrack, and certain Kelp species. The chemical structure and molecular weight of Fucoidan vary depending on the seaweed species from which it is extracted. For this reason, identifying the source species is an important consideration in Fucoidan research.

04. What Animal Studies Have Revealed

Study 1. Fucoidan Extracted from Okinawan Mozuku

·        Researchers administered fucoidan derived from Okinawan Mozuku to 8-week-old female BALB/c mice.

·        The Fucoidan had a purity of 88.3% and an average molecular weight of 49.8 kDa.

·        Oral doses ranged from 102.5 to 1,025 mg/kg per day over six weeks.

·        Each group consisted of 10 mice, and the results were compared with those of an untreated control group.

Key Findings: Compared with the control group, mice receiving Fucoidan showed significant increases in proliferation of splenic immune cells, macrophage phagocytic activity, interleukin-2 (IL-2), and serum antibodies (IgM, IgG, and IgA). Levels of IL-4, IL-5, and IgE decreased significantly. Researchers interpreted these findings as evidence that Fucoidan modulated both cell-mediated and humoral immune responses in mice.

Source (PubMed): https://pubmed.ncbi.nlm.nih.gov/31554251/ (PMID: 31554251)

Study 2. High-Molecular-Weight Fucoidan Derived from Wakame

·        Researchers investigated high-molecular-weight Fucoidan derived from Undaria pinnatifida (wakame).

·        The study included cell experiments and oral administration in a rat model of immunosuppression induced by cyclophosphamide, a medication used to suppress immune function.

Key Findings: Compared with the immunosuppressed model group, Fucoidan-treated animals showed improvements in natural killer (NK) cell activity, hematological parameters, cytokine markers in serum and spleen, and gut microbiome diversity. These findings suggest that Fucoidan may influence certain immune-related responses and the gut microbiome in this experimental model.

Source (PubMed): https://pubmed.ncbi.nlm.nih.gov/39024753/ (PMID: 39024753)

Study 3. Fucoidan and Aging in Mice

·        Researchers at the University of Rochester investigated Fucoidan derived from Fucus species in 15-month-old mice, an age roughly corresponding to middle age in humans.

·        Fucoidan was provided through drinking water and food, and the animals were monitored for the remainder of their lives.

Key Findings: Male mice receiving Fucoidan had a 13% longer median lifespan than control mice (p = 0.009). Both male and female mice showed lower frailty scores and reduced epigenetic age, as measured by DNA methylation markers, compared with controls. The researchers proposed that these effects might be associated with activation of SIRT6, a protein involved in cellular processes related to aging and longevity.

Important Note: This study is currently available as a preprint and has not undergone peer review. Its findings are preliminary and may change following further scientific evaluation.

Source (bioRxiv Preprint): https://www.biorxiv.org/content/10.1101/2025.03.24.645072

Important Research Limitation: All three studies described above were conducted in animals, with the second study also including cell-based experiments. These findings do not establish that Fucoidan improves immune function, extends lifespan, or prevents disease in humans. Additional well-designed human clinical studies are needed to determine whether these experimental findings have clinical relevance.

05. What to Look for When Choosing a Fucoidan Supplement

Fucoidan products can vary considerably depending on the species of brown seaweed used, geographic origin, and purity of the extracted ingredient. Rather than relying solely on advertising claims, consumers may find it helpful to review the following information on product labels and specifications.

What to Check	Why It Matters
Brown Seaweed Species	Fucoidan from Mozuku, Mekabu, and Fucus differs in polysaccharide structure. Combining Fucoidan from two or three seaweed species may offer complementary characteristics, although additional research is needed to determine whether such combinations provide greater health benefits.
Actual Fucoidan Content	Check whether the label specifies the actual amount of Fucoidan rather than only the total weight of the Fucoidan-containing extract.
Geographic Origin	Environmental conditions and water quality in harvesting areas may influence the presence of contaminants, including heavy metals. Identifying the source region and reviewing appropriate safety testing can help consumers evaluate product quality.
High Purity (85% or Higher)	Fucoidan purity of 85% or higher may indicate a more concentrated extract. However, purity alone does not establish biological effectiveness, and no universally accepted clinical threshold guarantees efficacy.

Product specifications and labeled amounts may vary by manufacturer and over time. Always review the most current product label and ingredient information before purchasing.

06. Today’s Healthy Aging Checklist

·        Have you reviewed your basic immune-health habits, including sleep, exercise, and balanced nutrition?

·        Have you discussed recommended vaccinations, including influenza and shingles vaccines, with your healthcare provider?

·        If you regularly include seaweed in your diet, have you considered its source and the amount you consume?

·        If you are considering a Fucoidan supplement, have you compared the labeled source ingredients, Fucoidan content, and purity information?

·        If you take medications, have you consulted your healthcare provider before starting a new supplement?

FDA Disclaimer

These statements have not been evaluated by the Food and Drug Administration (FDA). This product is not intended to diagnose, treat, cure, or prevent any disease.

Health and Product Information Disclaimer

This content is intended for general health education and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.

References

1. Tomori M, et al. Evaluation of the Immunomodulatory Effects of Fucoidan Derived from Cladosiphon okamuranus Tokida in Mice. Marine Drugs. 2019;17(10):547. https://pubmed.ncbi.nlm.nih.gov/31554251/

2. High-molecular-weight fucoidan exerts an immune-enhancing effect in RAW 264.7 cells and cyclophosphamide-induced immunosuppression rat by altering the gut microbiome. International Immunopharmacology. 2024;139:112677. https://pubmed.ncbi.nlm.nih.gov/39024753/

3. Murai U, Yamagishi K, Kishida R, Iso H. Impact of seaweed intake on health. European Journal of Clinical Nutrition. 2021;75(6):877–889. https://pubmed.ncbi.nlm.nih.gov/32908248/

4. Food and Agriculture Organization of the United Nations (FAO). Jeju Haenyeo Fisheries System, Republic of Korea (GIAHS). https://www.fao.org/giahs/giahsaroundtheworld/designated-sites/asia-and-the-pacific/jeju-haenyeo/detailed-information/ar/

5. Food and Agriculture Organization of the United Nations (FAO). The haenyeo women divers of Jeju Island. https://www.fao.org/newsroom/story/heritage-of-the-deep/en

6. Biashad SA, et al. SIRT6 activator fucoidan extends healthspan and lifespan in aged wild-type mice. bioRxiv preprint, 2025 (not peer reviewed). https://www.biorxiv.org/content/10.1101/2025.03.24.645072