The world's oldest man has celebrated his 113th birthday by sharing his secret to living a long life.

Francisco Nunez Olivera was born on December 13, 1904 in the village of Bienvenida in Badajoz, western Spain, where he has lived all his life.

He began his milestone day with his traditional piece of sponge cake and a glass of milk before opening birthday letters from across the world.

Affectionately known as Marchena to his family and friends, Olivera is in good health and is taken care of by his 82-year-old daughter Maria Antonia, the Metro reports.

She said her father is in "good health" and doesn't suffer from any aches, pains or illnesses that often plague seniors.  

"Some days he talks all day and others he sleeps all day," she said.

In total, Olivera has four children, nine grandchildren and 15 great-grandchildren. He has two sisters aged 97 and 93, and became the world's oldest man following the death of Polish-born Israeli Yisrael Kristal this past August.

When discussing his longevity, he said there's only two things that have kept alive for all these years.

Olivera said he simply owes his long life to a diet of home-grown vegetables and a daily glass of red wine.

On the contrary, others have linked his longevity to his living environment.

"He's an living example of the quality of life in the municipality, but also of the pollution-free skies and countryside and stress-free work of the traditional way of life," Mayor Antonio Carmona told Daily Mail.

According to his relatives, Olivera started to read again at 98-years-old after he underwent a cataract operation, one of only two occasions he has been to hospital. Having worked in the fields all his life, he would go on daily walks around his village until he turned 107.

In an April 2015 interview with Spanish daily newspaper El Mundo, Olivera said he hopes to live for a few more years despite outliving all of his friends.  

"I know I'm old but I don't feel old," he said.

Would you like to live to be 113 years old?