Birth control pills contains a combination of female hormones that prevent pregnancy by stopping ovulation, the release of an egg from the ovaries. Birth control pills secondarily prevent pregnancy by changing the uterine lining and cervical mucus to make it harder for sperm to reach the uterus and for an embryo to implant. Several dietary and herbal supplements can interfere with the efficacy of birth control pills, causing hormones to fluctuate and possibly resulting in pregnancy.
St. John's Wort
St. John's wort, also known as hypericum or goatweed, is a yellow flower used to treat mild to moderate depression. St. John's wort is the most well-known herbal supplement to interact with hormonal methods of contraception. According to a 2005 study published in the journal, Contraception, women taking a certain type of birth control pill who were treated with 300mg of St. John's wort three times daily had 15 percent less contraceptive hormones in their bloodstream, increased breakthrough bleeding and increased possibility of ovulation.
Vitex, also known as chasteberry and monk's pepper, is the fruit of the chaste tree. Vitex is used to treat symptoms of premenstrual syndrome, or PMS, menopause, acne and infertility. Vitex may help with these syndromes due to its ability to influence hormonal levels. However, this means vitex could modulate hormone levels in women taking birth control pills, rendering them less effective. The National Center for Complementary and Alternative Medicine, or NCCAM, a division of the National Institutes of Health, recommends that women taking hormonal contraceptives do not take vitex.
Dong quai, scientifically known as Angelica sinensis, is a member of the celery plant family. The plant grows in China, Korea and Japan and the root is used to treat PMS, menopause, cramps and irregular periods. A 2006 study in rats published in Phytotherapy Research found dong quai had estrogen-like effects and changed the estrous cycle. Dong quai's manipulation of female hormones means it may be unsafe to take dong quai with hormonal forms of contraceptives.
Black cohosh, also known as rattleweed, bugbane, bugwort and black snakeroot, is a member of the buttercup family. Black cohosh is used to treat symptoms of menopause, PMS and arthritis as well as to induce labor. Black cohosh is able to modulate menopause and PMS symptoms because of its ability to modulate female hormones. However, this is also the reason why black cohosh may interfere with the effectiveness of female hormonal birth control methods.
Red clover, also known as cow clover and wild clover, is a member of the legume family. Red clover is used to treat menopause, menstrual cycle-related breast pain, cancer, respiratory problems, osteoporosis, high cholesterol and prostate enlargement. Because red clover contains phytoestrogens, which are estrogen-like natural chemicals, red clover may decrease the efficacy of birth control pills.