A New Zealand woman's two-gallons-a-day Coca-Cola habit probably contributed to her death, experts have said.

Natasha Harris, a 30-year-old mother of eight, from Invercargill, died of a heart attack in 2010.

Fairfax Media said a pathologist has now said she probably suffered from hypokalemia, or low potassium, which was caused by excessive consumption of Coke and overall poor nutrition.

Ms Harris's partner said she drank up to 2.6 gallons (10 litres) of regular Coke every day. He also said she ate little and smoked about 30 cigarettes a day.

The coroner's office is compiling a final report on Ms Harris' death.

A spokeswoman for the soft-drinks giant said its products are safe and pointed out that even water can be deadly in excessive amounts.