Objectives　To evaluate the safety of an oyster extract-based, liquid-form dietary supplement“Watanabe Oyster Drink”.
Methods　With the use of“Watanabe Oyster Drink”containing 2000 mg of oyster extract per 50 mL in a bottle as the study drink, two clinical studies were performed in a total of 40 healthy male and female adults. In the first study designed as an excessive dosing study（Study I）, 5, 12 and 12 subjects received 1 bottle of oyster extract-free placebo drink, 1 bottle of study drink and 3 bottle of study drink, respectively, daily for 4 weeks with a subsequent 2-week follow-up period. In the second study designed as a long-term dosing study（Study II）, 11 subjects received a bottle of study drink daily for 12 weeks. Medical inspection, physical examinations and laboratory tests were conducted at the end of 4-week intervention and at the end of 2-week follow-up in the Study I and at weeks 4, 8 and 12 of intervention in the Study II.
Results　Two, 2 and 3 subjects in the placebo, regular dose and 3-fold increased dose groups, respectively, in the Study I and 1 subject in the Study II reported various types of adverse events, such as gastralgia and diarrhea, which were judged by the medical investigator that their relationship with the intervention was unable to be ruled out. All these adverse events were mild in extent and transient in occurrence and appeared to have no clinical significance. Throughout the two studies, there was no subject who had any intervention-related laboratory test abnormalities. The study group-based analyses of laboratory data showed that there were no clinically abnormal changes of any demographic, physical or laboratory test parameters in the two studies.
Conclusion　Intakes of the study drink in daily doses up to 3 bottles（6000 mg as oyster extract）for 4 weeks and those in a daily dose of 1 bottle（2000 mg as oyster extract）for 12 weeks were well tolerated and thus considered to be safe in healthy adults.