They're proven to help prevent pregnancy, and new evidence suggests birth control pills may also prevent one type of cancer.
A recent study found that birth control pills reduced the risk of endometrial cancer, or cancer of the uterus.
The authors of this study estimated that use of the pill may have prevented about 400,000 cases of cancer.
“The strong protective effect of oral contraceptives against endometrial cancer — which persists for decades after stopping the pill — means that women who use it when they are in their 20s or even younger continue to benefit into their 50s and older, when cancer becomes more common,“ said lead study author Valerie Beral, FMedSci, of the University of Oxford, in a press statement.
Birth control pills, or oral contraceptives, contain the hormones progestin and estrogen, which prevent pregnancy.
Although there has been past evidence that birth control pills may prevent endometrial cancer, researchers were unsure how long the effect might last because endometrial cancer typically appears in middle-aged and older women.
For this study, Dr. Beral and team compared use of birth control pills in groups of women with and without endometrial cancer.
They found that women who took birth control pills were much less likely than those who didn't to have endometrial cancer. Also, the risk was lower for women who had taken the pill for a longer period of time.
For every five years of taking birth control pills, patients' endometrial cancer risk was decreased by one-fourth, Dr. Beral and team found.
For women in high-income countries, taking the pill for 10 years almost cut the rate of endometrial cancer at the age of 75 in half. In other words, the potential protective effect of birth control pills may last for years after the pills are taken.
“People used to worry that the pill might cause cancer, but in the long term the pill reduces the risk of getting cancer,” Dr. Beral explained.
The authors concluded that birth control pills may be effective in preventing endometrial cancer.
This study was published Aug. 4 in The Lancet Oncology.
The Medical Research Council and Cancer Research UK funded this research. Dr. Beral and team disclosed no conflicts of interest.