Theresa Rowley celebrated her 104th birthday on 1 January, 2018 and she is still in disbelief about the fact that she achieved the feat. A resident at the Sentinel Pointe Retirement Community, a care home, in Grand Rapids, Michigan, she gives credit to the most unlikely dietary habit for her longevity.

Rowley says she drinks at least one can of her favourite coke every day and, like many others, she too wonders how she has lived for so long. "I'm surprised that I'm 104. It just doesn't seem like I should be that old," she told WZZM.

Though she is unable to recall much about her past life, the Michigan resident claims she was born in 1914 in Illinois and her family later moved to North Dakota before finally settling in Michigan. Rowley moved to the care home when she was 89 and says she thought she would die by the age of 100.

"When I was 100, I thought I would never be 104. I thought I'd pass away by that time but it just didn't happen. Then I turn 101, and nothing happens," she added.

When asked why she drinks diet coke every day, Rowley answered, "I drink it because I like it. I'm going shopping, and I need more Diet Coke. I have a bag full of empty Diet Coke cans that I need to return to buy more Diet Coke."

Her diet, however, has puzzled researchers, who have previously claimed that diet sodas do more harm to a person's health than their drinkers can imagine.

"Diet sodas may have health downsides and may not even provide the benefits some people turn to them for, such as weight loss," the Consumer Report wrote in its findings.

"The strongest evidence so far links regular diet soda intake with cardiovascular conditions, such as stroke and heart attack, as well as type 2 diabetes and obesity (which are also risk factors for cardiovascular disease)," Dr Ralph L Sacco, MD, professor of neurology at University of Miami's Miller School of Medicine, said in the report.

But Rowley is not the only person who credits her weird diet to her longevity. Elizabeth Sullivan, who turned 104 in 2015, told CNN that she felt Dr Pepper soda was the secret to her long life.

"This stuff is good. It's got sugar in it. I have been to two doctors who told me, 'If I drink it, I'll die.' But they died first," she said.

Sullivan also claimed that she was not taking any medication but drank a bottle of the soda every day.