A 6‐month chronic toxicity study on green tea polyphenols in middle‐aged ovariectomized rats

Abstract

The project is to evaluate chronic toxicity and safety in middle‐aged ovariectomized rats supplemented with different dosages of green tea polyphenols (GTP) in drinking water. 182 SD were sham (n=39) or ovariectomized (OVX, n=143). Both sham and OVX‐control animals receiving no GTP were assigned for sample collection at baseline, 3, and 6 months. The remaining OVX animals were randomized into 0.15%, 0.5%, 1%, and 1.5% (wt/vol) GTP for 3 and 6 months. Routinely clinical observation was performed. Ophthalmologic examination (control, 1% and 1.5% GTP groups), blood for hematology and clinical chemistry, urine analysis were assessed at baseline, 3, and 6 months. Histologic examination was performed on all tissues from animals in both control and high dose groups at baseline and the end of study. No mortality or abnormal treatment‐related findings in clinical observations or ophthalmologic examinations were noted. No treatment‐related macroscopic or microscopic findings were noted for animals administered 1.5% GTP. There was no difference in baseline body weight among all OVX‐treated treatment groups. The OVX+1.5% GTP group had the smallest body weight of the OVX‐treated groups. No difference in food intake among all treatment groups. In all OVX‐treated groups, GTP supplementation decreased water consumption of rats in a dose‐dependent pattern. At 6 months, GTP intake did not affect complete hematology, clinical chemistry, and urinalysis, except for PO4 and BUN (increased); total cholesterol, BUN, LDH, and urine pH (decreased).This study reveals that the No‐Observed‐Effect Level (NOEL) of GTP is 1.5%, the highest dose used. Supported by NIH/NCCAM AT006691.