The aim of study was to evaluate the safety of Cladosiphon okamuranus fucoidan. Long-term ingestion study was conducted in volunteers（n＝30, 45.2±12.5 years old［mean±SD］）, who were randomized to the fucoidan drink group（500 mg of fucoidan daily for 12 weeks）or placebo group in a double-blind, parallel study. In addition, excessive ingestion study was conducted in volunteers（n＝30, 43.4±10.4 years old［mean±SD］）, who were randomized to the fucoidan drink group（2000 mg of fucoidan daily for 4 weeks）or the placebo group in a double-blind, parallel study.
　　The results of long-term and excessive ingestion studies showed that there were no side effects in the test period. In conclusion, these studies showed no abnormality in the medical questions, vital sign, hematological examination, serum biochemical examination, urinary test, subjective and objective any symptom.