Keeping hearts healthy naturally has become more important, following research which shows transplant risks from the opposite sex.

Researchers at John Hopkins University discovered people had a higher chance of dying when they received a heart from someone not of their own sex.

Investigators were unsure why this was, but believed it was due to differences in size.

At higher risk of rejection were men who received a women’s hearts over women who showed the same risks when receiving the organ from either sex.

Researcher Dr Eric Weiss said: "One of the messages that we don’t want to give is that people should be waiting for a same-sex transplant, because the rate of survival is clearly superior having a transplant to not having a transplant."

The results came from a review of data from 18,240 people who had a heart transplant administered by the United Network of Organ Sharing from 1998 to 2007.

According to the National Institutes of Health, 88 per cent of people survive the first year after surgery with a 72 per cent survival rate over the following five years.