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Oral contraceptives (OCs), or birth control pills, are some of the most effective contraceptive drugs.
These medications include:
Although the evidence is not consistent, women who are taking OCs may need extra folate.1-5
Since folate deficiency is fairly common even among women who are not taking OCs, and it's not wise to be lacking in an essential nutrient, taking a folate supplement on general principle is probably a good idea.
Evidence from several studies suggests that OCs might interfere with the absorption or metabolism of magnesium, vitamin B2, vitamin C, and zinc.6-12 With the exception of the trials involving magnesium, these studies used older, high-dose OCs. Modern, low-dose OCs may not affect nutrients to the same extent; still, you should probably make sure you get enough of these nutrients.
Reliable case reports, as well as controlled clinical trials, indicate that St. John's wort interferes with the effectiveness of oral contraceptives and may have led to unwanted pregnancies.13,20,25
Indole-3-carbinol (I3C) is a substance found in broccoli that is thought to have cancer preventive effects. One of its mechanisms of action is thought to involve facilitating the inactivation of estrogen, as well as blocking its effects on cells.21-24 The net result could be decreased effectiveness of oral contraceptives.
OCs have been reported to cause increased sensitivity to the sun, amplifying the risk of sunburn or skin rash. Because dong quai and St. John's wort may also cause this problem, taking these herbal supplements while taking OCs might add to this risk.
It may be a good idea to wear sunscreen or protective clothing during sun exposure if you take one of these herbs while using OCs.
Weak evidence hints that the herb rosemary may enhance the liver’s ability to deactivate estrogen in the body.26 This could potentially interfere with the activity of medications that contain estrogen.
Grapefruit juice slows the body's normal breakdown of several drugs, including estrogen, allowing it to build up to potentially excessive levels in the blood.14 A recent study indicates this effect can last for 3 days or more following the last glass of juice.15
If you take estrogen, the safest approach is to avoid grapefruit juice altogether.
The supplement resveratrol has a chemical structure similar to that of the synthetic estrogen diethylstilbestrol and produces estrogenic-like effects.16 For this reason, it should not be combined with prescription estrogen products.
One report has noted that an ingredient of milk thistle, silibinin, can inhibit a bacterial enzyme called beta-glucuronidase. This enzyme helps oral contraceptives work.17 Taking milk thistle could, therefore, reduce the effectiveness of OCs.
Androstenedione has become popular as a sports supplement, on the theory that it increases testosterone levels as well as sports performance. However, there is no evidence that it is effective. In addition, androstenedione appears more likely to elevate estrogen than testosterone levels. This could increase risks of developing estrogen-related diseases, including breast and uterine cancers. Women taking estrogen should not take androstenedione.18
Fears have been expressed by some experts that soy or soy isoflavones might interfere with the action of oral contraceptives. However, one study of 36 women suggests that such concerns are groundless.19
1. Martinez O and Roe DA. Effect of oral contraceptives on blood folate levels in pregnancy. Am J Obstet Gynecol 128: 255-261, 1977.
2. Steegers-Theunissen RP, Van Rossum JM, Steegers EA, et al. Sub-50 oral contraceptives affect folate kinetics. Gynecol Obstet Invest 1993;36:230-233.
3. Mooij PNM, Thomas CMG, Doesburg WH, et al. Multivitamin supplementation in oral contraceptive users. Contraception 1991;44:277-288.
4. Shojania AM, Hornady G, and Barnes PH. Oral contraceptives and serum-folate level. Lancet 1968;1:1376-1377.
5. Whitehead N, Reyner F, and Lindenbaum J. Megaloblastic changes in the cervical epithelium. Association with oral contraceptive therapy and reversal with folic acid. JAMA 1973;226:1421-1424.
6. Larsson-Cohn U. Oral contraceptives and vitamins: a review. Am J Obstet Gynecol 1975;121:84-90.
7. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-564.
8. Webb JL. Nutritional effects of oral contraceptive use: a review. J Reprod Med 1980;25:150-156.
9. Rivers JM and Devine M. Plasma ascorbic acid concentrations and oral contraceptives. Am J Clin Nutr 1972;25:684-689.
10. Briggs M and Briggs M. Vitamin C requirements and oral contraceptives. Nature 1972;238:277.
11. Seelig MS. Increased need for magnesium with the use of combined oestrogen and calcium for osteoporosis treatment. Magnes Res 1990;3:197-215.
12. Blum M, et al. Oral contraceptive lowers serum magnesium. Harefuah 1991;3:363-364.
13. Jobst KA, McIntyre M, St. George D, et al. Safety of St John's wort (Hypericum perforatum).Lancet 2000;355:575.
14. A to Z Drug Facts [book on CD-ROM]. 2nd ed. St. Louis, MO: Facts and Comparisons; 2000.
15. Takanaga H, Ohnishi A, Murakami H, et al. Relationship between time after intake of grapefruit juice and the effect on pharmacokinetics and pharmacodynamics of nisoldipine in healthy subjects. Clin Pharmacol Ther 2000;67:201-214.
16. Gehm BD, McAndrews JM, Chien PY, et al. Resveratrol, a polyphenolic compound found in grapes and wine, is an agonist for the estrogen receptor. Proc Natl Acad Sci U S A 1997;94:14138-14143.
17. Kim DH, et al. Silymarin and its components are inhibitors of beta-glucuronidase. Biol Pharm Bull 1994;17:443-445.
18. Leder BZ, Longcope C, Catlin DH, et al. Oral androstenedione administration and serum testosterone concentrations in young men. JAMA 2000;283:779-782.
19. Martini MC, Dancisak BB, Haggans CJ, et al. Effects of soy intake on sex hormone metabolism in premenopausal women. Nutr Cancer 1999;34:133-139.
20. Gorski JC, Hamman MA, Wang Z, et al. The effect of St. John's Wort on the efficacy of oral contraception [abstract MPI-80]. American Society for Clinical Pharmacology and Therapeutics Annual Meeting, March 24-27; Atlanta, GA; 2002.
21. Michnovicz JJ. Increased estrogen 2-hydroxylation in obese women using oral indole-3-carbinol. Int J Obes Relat Metab Disord. 1998;22:227-229.
22. Bradlow HL, Sepkovic DW, Telang NT, et al. Multifunctional aspects of the action of indole-3-carbinol as an antitumor agent. Ann N Y Acad Sci. 1999;889:204-213.
23. Yuan F, Chen DZ, Liu K, et al. Anti-estrogenic activities of indole-3-carbinol in cervical cells: implication for prevention of cervical cancer. Anticancer Res. 1999;19:1673-1680.
24. Meng Q, Yuan F, Goldberg ID, et al. Indole-3-carbinol is a negative regulator of estrogen receptor-alpha signaling in human tumor cells. J Nutr. 2000;130:2927-2931.
25. Pfrunder A, Schiesser M, Gerber S, et al. Interaction of St John's wort with low-dose oral contraceptive therapy: a randomized controlled trial. Br J Clin Pharmacol. 2003;56:683-690.
26. Zhu BT, Loder DP, Cai MX, et al. Dietary administration of an extract from rosemary leaves enhances the liver microsomal metabolism of endogenous estrogens and decreases their uterotropic action in CD-1 mice. Carcinogenesis. 1998;19:1821-1827.
Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015