More promiscuous people are more likely to get cancer in old age, according to a study.
Researchers found that having 10 or more sexual partners over a lifetime almost doubled the risk of a woman developing cancer, and raised it by two thirds for men.
A link between sexually-transmitted infections and cancers – HPV, for example, is known to raise the risk of diseases in the cervix and penis – could be to blame.
And people who had sex with more partners also tended to drink more alcohol and smoke more cigarettes, the scientists said – but they also did more exercise.
The finding was no reason to avoid having sex, they added, and said that intercourse brings a variety of physical and mental health benefits which outweighed the longer-term risk.
Researchers said that a higher risk of catching STIs could translate to a higher risk of developing cancer (stock image)
Researchers from Anglia Ruskin University, Cambridge, collected data from nearly 6,000 men and women over the age of 50.
Among men, those who reported more than 10 lovers in their lives had a 69 per cent higher chance of getting cancer, compared with those who had bedded only one or none.
Women who reported 10 or more sexual partners were found to be 91 per cent more likely to have been diagnosed with cancer.
Only 486 men (19 per cent) and 239 women (7.5 per cent) admitted to having had sex with 10 or more people.
Dr Lee Smith, an Anglia Ruskin University expert and the author of the study, told MailOnline: 'We expected there to be an association between number of sexual partners and cancer risk as previous research has shown that specific STIs may lead to several cancers.
'Indeed, a higher number of sexual partners means greater potential exposure to STIs. It is interesting that the risk is higher in women when compared to men.
'This may be because the link between certain STIs and cancer is stronger in women, such as HPV (Human papillomavirus) and cervical cancer compared to HPV and penile cancer.'
People in the study, which was published in the journal BMJ Sexual and Reproductive Health, had an average age of 64 and most were married.
The most common category for both sexes was one or no sexual partners – 785 out of 2,537 men and 1,285 out of 3,185 women.
In both sexes, people with a more colourful sexual history also tended to be younger, single and in either the richest or the poorest communities.
And those who reported a higher tally of sexual partners were also more likely to smoke, drink frequently, and do more vigorous physical activity on a weekly basis, the study found.
Clinics are 'struggling' to cope with soaring numbers of STIs because dating apps are encouraging casual sex, experts have warned warned.
Cases of syphilis rose by half in Wales between 2016 and 2017, and record numbers of over-65s are getting syphilis, gonorrhoea and chlamydia in England, figures have shown.
Experts and doctors in the field have warned the fast turnaround of partners and rise in casual sex fuelled by online dating apps may be making catching an STI more likely.
And they also make it more difficult to contact past partners, who may not have mutual friends.
Dr Olwen Williams, president of the British Association of Sexual Health and HIV told the BBC in October: 'The frequency of app hook-ups and dating apps used as a sort of medium to access sexual activity seems to have increased significantly.
'What we can say about sexual mixing and sexual networking is that things have changed considerably.
'We're seeing a genuine rise in STIs. If we were just seeing an increase in testing then our figures would look slightly different, but it feels that way.
'Certainly in my career I've never seen so much gonorrhoea or syphilis in my area, ever.'
When all the data was analysed, a significant association emerged between the number of lifetime sexual partners and risk of a cancer diagnosis among both sexes.
Participants were also asked to rate their own health and report any long standing condition or infirmity which impinged on routine activity in any way.
Researchers claim the