Hormonal control of ovulation has been available to women since the early 1960s with the introduction of "the pill." Initially, dosages of estrogen and progesterone were available only in pill form, but in 2011 they are offered as injections, patches and implants. All hormonal methods prevent ovulation by maintaining sex hormones at high levels throughout a woman's cycle. Some supplements may interfere with the actions of hormonal birth control, which can lead to unplanned pregnancies.
St. John's Wort
St. John's wort, or Hypericum perforatum, is usually prepared as an herbal tincture and used to treat mild depression and anxiety. It exerts its anti-anxiety and antidepressant effects by inhibiting the re-uptake of the neurotransmitters serotonin, dopamine and noradrenalin, which are brain chemicals responsible for mood. However, St. John's wort also stimulates certain enzymes to break down the estrogen in estrogen-based oral contraceptives faster than normal, which reduces the amount of the hormone in the blood and the effectiveness of birth control, as cited in "Medical Herbalism: The Science Principles and Practices of Herbal Medicine." In essence, taking St. John's wort may be similar to taking a low-dose estrogen pill. Further, St. John's wort has been reported to cause bleeding in women taking oral contraceptives, which is a sign of diminished pill effect and possible contraceptive failure, as cited in "The Essential Book of Herbal Medicine." Additional birth control, such as a condom, is recommended if taking St. John's wort along with birth control pills.
Soy products contain isoflavones, such as genistein, which are classified as phytoestrogens. Phytoestrogens mimic the effect of the hormone estrogen within the body. In women, the effects of phyoestrogen are controversial because some studies have found they stimulate growth of estrogen-sensitive breast cancer cells, while others have found they offer some protection against breast cancer, as cited in "Nutrition and Public Health." Regardless, isoflavones are used to reduce the intensity of menopause-related hot flashes and may interfere with the effectiveness of oral contraceptives and hormone replacement therapy, according to "Biochemical, Physiological and Molecular Aspects of Human Nutrition."
According to the University of Maryland Medical Center, mega-dosing vitamin C can cause a rise in estrogen levels when taken with oral contraceptives and hormone replacement drugs, particularly if the user is deficient in vitamin C to begin with. Oral estrogen-based birth control pills decrease the effects of vitamin C in the body, although it is unknown if large doses of vitamin C increase or decrease the effectiveness of the birth control. Absorption of estrogen may be increased.
Melatonin, a hormone secreted by the pineal gland within the brain in response to changing levels of light, promotes deep sleeps. As such, melatonin is important for the circadian rhythm, or internal body clock. Melatonin is also considered a "master control" hormone that regulates other hormones. Birth control pills seem to increase how much melatonin is secreted by the pineal gland, although supplementing with melatonin may have a negative impact on the effects of oral contraception. No human studies have been conducted to examine the effects, but consulting with a health professional before combining any supplement regimen with birth control pills is always recommended.