# Fucoidan (brown seaweed extract)

Source: https://onco.cc/technologies/fucoidan-seaweed/  
OnCo record `fucoidan-seaweed` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Fucoidan is a sugar-like compound from brown seaweed sold as an anticancer supplement. Small studies suggest it may ease fatigue and help some people stay on chemotherapy, but there is no proof it controls cancer. It thins the blood, so it can add to anticoagulants.

## Summary

Fucoidan is a sulfated polysaccharide from the cell walls of brown seaweeds. Memorial Sloan Kettering's About Herbs summary lists antitumour, antiangiogenic, antiviral and anti-inflammatory effects in laboratory and animal work. In small human studies, fucoidan given alongside treatment helped people with advanced cancer continue chemotherapy and regulated fatigue, lowered inflammatory cytokines, and, combined with transarterial chemoembolisation, was reported to improve control of hepatocellular carcinoma and preserve liver function; in locally advanced rectal cancer on chemoradiotherapy it was associated with better quality of life, less rash and less fatigue. A small study in breast cancer found no clinically significant interaction with letrozole or tamoxifen. Because fucoidan has anticoagulant and antithrombotic activity, MSK warns it may increase bleeding risk with warfarin or heparin. Diarrhoea has been reported and stopped when fucoidan was stopped.

## Fields

- Kind: Technology
- Status: phase-2
- Last checked: 2026-11-04
- Tags: complementary; supportive-care; evidence:insufficient
- Principle: Sulfated fucose polymers bind growth factors and selectins and modulate platelets and immune cells in laboratory models.
- Strengths: Small studies during chemotherapy and chemoradiotherapy; No interaction with letrozole or tamoxifen in one small study
- Limitations: Studies small; no survival endpoint; Anticoagulant effect adds to blood thinners

## Sources

- MSK About Herbs: Fucoidan (page last updated 14 May 2026): https://www.mskcc.org/cancer-care/integrative-medicine/herbs/fucoidan

## Connected records

- technologies: [Dietary supplements during cancer treatment: interactions and harms](https://onco.cc/technologies/dietary-supplements-treatment-interactions/), [Evidence-based integrative oncology](https://onco.cc/technologies/integrative-oncology/), [MGN-3 (rice bran arabinoxylan, BioBran)](https://onco.cc/technologies/mgn-3-rice-bran-arabinoxylan/), [Sea cucumber extract](https://onco.cc/technologies/sea-cucumber-extract/)
- fronts: [Diet, Exercise & Lifestyle](https://onco.cc/fronts/nutrition-lifestyle/), [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)
- drugs: [Letrozole (and other aromatase inhibitors)](https://onco.cc/drugs/letrozole/), [Tamoxifen](https://onco.cc/drugs/tamoxifen/)
- bottlenecks: [Toxicity and quality of life are undervalued](https://onco.cc/bottlenecks/b-toxicity-qol/)

---
JSON: https://onco.cc/api/v1/entities/fucoidan-seaweed.json