The modern contraceptive pill—a combination of two hormones, estrogen and progestin—fools the body into thinking its pregnant and prevents the release of eggs to be fertilized. But hormones are powerful chemicals and they have other effects—some of which can be beneficial.
A new meta-analysis in the Lancet Oncology of 63 studies involving 27,000 women weeds out differences between smaller studies to draw an overarching conclusion: the use of oral contraceptives is linked to lower risk of womb cancer.
Even better, the analysis reveals that benefits last much longer—for as long as 30 years after you stop consuming the pill. For those who have taken the pill for 10 years, the risk of womb cancer before the age of 75 is halved. The exact mechanism of why this occurs is not yet clear—but it may have to do with how these hormones regulate cell-proliferation, which can lead to cancer if things go wrong.
As many as 400 million women in developed countries alone have used the pill for often prolonged periods of time. Looking at the reduction in cancer risk, the authors estimate that the pill has prevented 400,000 cases of cancer in the last 50 years and as many as 200,000 cases in just the last decade.
Beyond womb cancer, however, the pill has mixed impact on other types of cancer. It increases the risks of some types and protects against others. Fortunately, according to the Cancer Research UK, any increased risk of cancer starts subsiding after you stop taking the pill. For these other cancers:
Breast and cervical cancer: Those on the pill have slightly higher risk of breast cancer and cervical cancer. But the risk starts to drop once you stop taking the pill. In both cases, 10 years later, the risk is back to normal.
Ovarian cancer: The longer you take the pill, the lower your risk of ovarian cancer. The protection is endowed because the pill suppresses the stimulation of ovaries.
Bowel cancer: Those who have taken the pill have a 20% lower risk of bowel cancer, but the strength of the link will need to be verified with more studies.