The purpose of this study was to determine the effects of 6-OXO, a purported nutritional
aromatase inhibitor, in a dose dependent manner on body composition, serum hormone levels, and
clinical safety markers in resistance trained males. Sixteen males were supplemented with either
300 mg or 600 mg of 6-OXO in a double-blind manner for eight weeks. Blood and urine samples
were obtained at weeks 0, 1, 3, 8, and 11 (after a 3-week washout period). Blood samples were
analyzed for total testosterone (TT), free testosterone (FT), dihydrotestosterone (DHT),
estradiol, estriol, estrone, SHBG, leutinizing hormone (LH), follicle stimulating hormone (FSH),
growth hormone (GH), cortisol, FT/estradiol (T/E). Blood and urine were also analyzed for clinical
chemistry markers. Data were analyzed with two-way MANOVA. For all of the serum hormones,
there were no significant differences between groups (p > 0.05). Compared to baseline, free
testosterone underwent overall increases of 90% for 300 mg 6-OXO and 84% for 600 mg,
respectively (p < 0.05). DHT underwent significant overall increases (p < 0.05) of 192% and 265%
with 300 mg and 600 mg, respectively. T/E increased 53% and 67% for 300 mg and 600 mg 6-OXO,
respectively. For estrone, 300 mg produced an overall increase of 22%, whereas 600 mg caused a
52% increase (p < 0.05). Body composition did not change with supplementation (p > 0.05) and
clinical safety markers were not adversely affected with ingestion of either supplement dose (p >
0.05). While neither of the 6-OXO dosages appears to have any negative effects on clinical
chemistry markers, supplementation at a daily dosage of 300 mg and 600 mg for eight weeks did
not completely inhibit aromatase activity, yet significantly increased FT, DHT, and T/E.