If you think daily exercise and a healthy diet were the key to a long life, think again.

Scientists say that the secret to living more than 100 years comes down to a hardy immune system, thanks to an abundance of a particular infection-fighting white blood cell.

In a study coordinated by scientists at Japans RIKEN Center for Integrative Medical Sciences (IMS) and Keio University School of Medicine, researchers discovered that supercentenarians those aged over 110 years have an excess of cytotoxic CD4 T-cells.

These super immune system cells, according to the study published in Proceedings of the National Academy of Sciences (PNAS), are more aggressive and known to kill any damaged cell that crosses its path, such as virus-infected or cancer cells.

We believe that this type of cells, which are relatively uncommon in most individuals, even young, are useful for fighting against established tumors, and could be important for immunosurveillance, said Piero Carninci, deputy director of RIKEN, in a statement. This is exciting as it has given us new insights into how people who live very long lives are able to protect themselves from conditions such as infections and cancer.

Scientists noticed that most of Japans supercentenarians had managed to dodge illness most of their lives, leading them to believe their advanced age might have something to do with their extraordinary immune systems.

To find out, they pulled a total of 41,208 immune cell samples from seven supercentenarians, and 19,994 cells from younger individuals ages 50 to 89. They found that while both groups had about the same number of T-cells altogether, the supercentenarians had an excess of the unique cytotoxic CD4 T-cells.

This finding might help explain why so many centenarians will say that drinking booze regularly didnt stop them from reaching 100. Others, though, credit a life without the stress of marriage or children as helping them to outlast their peers.

Amparo Perez, 105, told The Post she doesnt regret never remarrying when her first husband died. No aggravation, she said, [is] the most important thing, not to have aggravation.

Caroline Binns, 101, would agree that husbands were only trouble. She told The Post last year, Id rather be left in peace, not in pieces.

Her friend, 101-year-old Lucille Watson, said dancing and cheesecake inspires her to get out of bed every morning: Lifes pleasures are meant to be enjoyed.

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110-year-olds live so long thanks to 'super' immune systems: study - New York Post