| Abstract: | Researchers compared data on 30 25-35 year old women who took the combined oral contraceptive (OC) Ovlar (0.05 mg ethinyl estradiol and 0.5 mg dinorgestrel) for 2-5 years with data on 10 women who did not take OCs to determine the longterm effect of Ovlar on vitamin B6 metabolism and urinary Xanthurenic acid (XA). Cases received either 50 mg or 100 mg of vitamin B6 tablets every day for 4 weeks. Mean XA excretion/24 hours stood much higher among OC users than among the controls (12.51 vs. 2.33; p.01), e.g., XA excretion among OC users ranged from 3.45 to 34.95 mcg/24 hours. Among the OC users, mean urinary XA excretion/24 hours was significantly higher before 50 mg vitamin B6 administration than it was after its administration (13.5 mcg vs. 2.71 mcg; p.01). Administration of 100 mg vitamin B6 had the same effect (11.52 mcg vs. 2.26 mcg; p.01). XA excretion was basically the same for the 2 OC user groups (50 mg and 100 mg administration of vitamin B6). Both doses of vitamin B6 brought about comparable XA excretion levels as the control group. The researchers concluded that 50 mg of vitamin B6 taken daily for 4 weeks is sufficient to correct vitamin B6 deficiency and changed metabolism among OC users. Research has demonstrated that OCs alter vitamin B6 tryptophan metabolism in 2 ways. They increase hepatic tryptophan oxygenase activity resulting in a surplus of tryptophan further in the pathway to niacin. This effect explains the higher production of several metabolites. OCs also reduce the proclivity for kynureninase, the pyridoxal phosphate of vitamin B6 dependent enzyme of tryptophan metabolism perhaps increasing the need for plasma pyridoxal phosphate. |
