A 30-year-old New Zealand woman's habit of drinking several litres of Coca-Cola a day probably contributed to her death, doctors testifed at an inquest this week.

Natasha Harris, a stay-at-home mother of eight from Invercargill, died of a heart attack in February, 2010.

A pathologist, Dr. Dan Mornin, testified at the inquest Thursday that Harris' heart attack was caused by cardiac arrhythmia (abnormal heart rhythm), Fairfax Media reported.

He added it was likely she was suffering from hypokalemia (low potassium) a condition that can lead to abnormal heart rhythms. He said be believed the condition was likely caused by her excessive consumption of cola and overall poor nutrition.

Mornin said that Harris also had toxic levels of caffeine, a stimulant found in most colas, which also may have contributed to her death.

Harris' partner, Chris Hodgkinson, testified that Harris regularly drank between 4.5 and 10 litres of Coke every day, averaging about seven litres a day.

"The first thing she would do in the morning was to have a drink of Coke beside her bed and the last thing she would do at night was have a drink of Coke," Hodgkinson said in a deposition.

"She was addicted to Coke," he said adding that if she didn't have her daily dose of Coke, she got moody, had headaches and was low in energy.

He said he had known Harris since she was 16 and she had always drank Coke. But he said in the last seven or eight years of her life, she had increased her habit from a couple of 1.5-litre bottles a day up to five bottles a day.

Hodgkinson said Harris ate little and smoked more than a pack of cigarettes a day. Harris also had severe dental problems and all her teeth had been removed.

In the months before her death, he said, Harris felt sick all the time, experienced blood pressure problems and lacked energy. She had pain in her stomach and complained her heart would "pump like mad," Hodgkinson said.

He said he never suspected the Coke was making her ill.

"I never thought about it. It's just a soft drink, just like drinking water. I didn't think a soft drink was going to kill her," he said.

Another pathologist, Dr. Martin Sage, said in a deposition that "it is certainly well demonstrated that excessive long or short term cola ingestion can be dramatically symptomatic, and there are strong hypothetical grounds for this becoming fatal in individual cases."

Hodgkinson said he thinks cola drinks should come with warning label, saying that might have reduced the amount Harris drank.

"I know she wouldn't have wanted to die and leave her eight children with no mother," he said.

Karen Thompson, a spokeswoman for Coca-Cola Oceania, said in a statement that its products are safe.

"We concur with the information shared by the coroner's office that the grossly excessive ingestion of any food product, including water, over a short period of time with the inadequate consumption of essential nutrients, and the failure to seek appropriate medical intervention when needed, can be dramatically symptomatic."

Drinking too much water in a short period can lead to a condition known as water intoxication. The condition can cause hyponatremia, which is the dilution of sodium and other electrolytes needed to maintain basic heart and brain functions.

The coroner's office is expected to issue a final report on the death soon.

With a report from the Associated Press