Using the pill, even for just a few years, offers significant long-term protection against womb cancer, a major new study has shown.

According to the findings, the drug's use has probably prevented as many as 400,000 cases of the disease in high-income countries over the last 50 years.

Oral contraceptives, known commonly as the pill, are one of the most popular types of contraception used by women worldwide. UK researchers set out to assess the pill's impact on endometrial cancer.

The endometrium is the lining of the womb and around 300 women in Ireland are diagnosed with the disease every year.

The researchers looked at 36 studies from around the world, which involved over 27,000 women with endometrial cancer. They found that the pill offers substantial long-term protection against this type of cancer, and the longer it is used, the bigger the reduction in risk.

"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," explained the study's author, Prof Valerie Beral, of the University of Oxford.

The researchers estimated that between 1965 and 2014, around 400,000 cases of endometrial cancer were prevented in high-income countries as a result of women using the pill. In the last decade alone (2005 - 2014), some 200,000 cases have been prevented.

The study revealed that for every five years of oral contraceptive use, the risk of endometrial cancer reduces by about a quarter.

The researchers said that the current evidence suggests that ‘medium-to-long-term use of oral contraceptives (i.e. for five years or longer) results in substantially reduced risk of endometrial cancer'.

"Previous research has shown that the pill also protects against ovarian cancer. People used to worry that the pill might cause cancer, but in the long term the pill reduces the risk of getting cancer," Prof Beral added.

Details of these findings are published in the journal, The Lancet Oncology.