Taking the contraceptive pill could protect women from the worst effects of the flu, scientists claim.
Progesterone, found in most forms of birth control helps to stave off influenza, a study discovered.
When infected, levels of the hormone in the body decline – but certain forms of contraception allow for more of it to remain in the system.
Women of reproductive age are twice as likely as men to suffer from complications related to the flu.
But it is hoped the discovery means these hormones could one day be used as a treatment for the virus in women.
Progesterone, found in most forms of birth control, staves off the worst effects on influenza, researchers from Johns Hopkins University found
In an unexpected finding, the hormone also helped damaged lung cells heal quicker on mice.
When female mice get sick with the flu, their natural levels of progesterone fall, researchers from Johns Hopkins University found.
Women on hormonal contraceptives get a steadier level of the hormone which overrides what the ovaries make naturally.
They also help to reduce what the virus takes away during infection.
Lead researcher Dr Sabra Klein said: ‘Despite the staggering number of women who take this kind of birth control, very few studies are out there that evaluate the impact of contraceptives on how the body responds to infections beyond sexually-transmitted diseases.
When infected, levels of the hormone in the body decline. But forms of contraception which contain progesterone allow for more to enter the system to improve lung function
‘Understanding the role that progesterone appears to play in repairing lung cells could really be important for women’s health.
‘When women go on birth control, they don’t generally think about the health implications beyond stopping ovulation and it’s important to consider them.’
Researchers placed progesterone implants in female mice and left other mice, also female, without. They were then infected with influenza A virus.
OTHER BENEFITS OF THE PILL
Ovarian cancer rates among British women have dropped by more than a fifth in a decade, a major study found.
Experts say the 22 per cent fall is down to rising use of the contraceptive Pill – which protects against ovarian cancer – and declining use of HRT, thought to increase the risk.
Ovarian cancer is the sixth most common form of the disease among British women, with almost 7,300 cases diagnosed each year and 4,128 deaths.
Both sets of mice became ill, but those which had the implants had less pulmonary inflammation.
They also had better lung function and saw the damage to their lung cells repaired more quickly.
The hormone protected female mice from more serious effects of the flu by increasing the production of a protein called amphiregulin.
When the researchers bred mice depleted of the protein, the protective effects of progesterone disappeared as well.
The findings were published in the journal PLOS Pathogens.
The World Health Organisation (WHO) has reported more than 100 million women around the world are on progesterone-based contraception.
They have already listed hormonal contraceptives as essential medication because of the benefits they have on women’s health.
Previous research has found they widen the interval between pregnancies, decrease rates of maternal mortality and improve outcomes for babies and children.