Sex is good for the heart, say scientists - but only if you're a man
Sex is good for the heart because it reduces the levels of a harmful chemical in the blood, scientists believe - but the effect is only seen in men.
Having sex several times a week can cut lead to better circulation and healthier blood vessels in men, which researchers say is crucial for preventing a build-up of the chemical homocysteine.
But scientists say women benefit much less because sexual arousal is less dependent on having a healthy blood flow, which is a key factor in keeping homocysteine under control.
Heart disease is the biggest killer in Britain.
Doctors have long suspected that frequent sex can reduce the risks, but the latest findings, published in the Journal of Sexual Medicine, are the first to show it works by driving down homocysteine levels.
The chemical is a vital building block of proteins and occurs naturally in the body.
But excess levels, which can be caused by poor diet, are thought to damage blood vessels supplying the heart - raising the risk of a deadly clot forming.
Researchers from the National Defence Medical Centre in Taiwan tracked more than 2,000 men and women, aged from 20 to 59.
They analysed blood samples to measure levels of homocysteine and matched the results up with volunteers' sexual activity.
The results showed the lowest traces of the chemical were found in men claiming to have sex at least twice a week, while the highest readings were found in those restricted to less than once a month.
But in women there was no significant variation.
Researchers called on doctors to advice male patients at risk of heart disease to have more sex.
In a report on their findings they said: "This is the first study of its kind to evaluate the correlation between sexual frequency and homocysteine levels.
"A good quality sex life, frequent sex and libido are all related to health in the middle-aged and elderly.
"Increased sexual frequency could have a protective effect on general health and quality of life - especially in men - so doctors should support patients' sexual activity.'
Dr Mike Knapton from the British Heart Foundation said the study produced an "interesting result" but did not prove regular sex reduced homocysteine levels.
He said: "A relationship does exist between sex and heart disease risk.
"Checking your blood pressure and cholesterol, as well as keeping active and not smoking, remain the best ways to ensure a healthy future."
A major review of scientific data in 2015 found raised homocysteine levels increased the risk of death from heart disease by 66 per cent.
And last year experts at Boston University discovered the chances of a stroke jumped by almost a third in those with high readings.
It has also been linked with Alzheimer's disease and cancer.