Swapping butter for canola or olive oil could slash the risk of an early death, new US research suggests.

Experts examined data for more than 221,000 adults, who were followed up for 30 to 50 years, and found butter actually seemed to drive up the risk of dying.

Over time, some 50,932 deaths were documented among the group, with 12,241 due to cancer and 11,240 due to heart disease.

After adjusting for other factors, people in the group who had the highest butter intake had a 15 per cent higher risk of dying from any cause compared with those with the lowest intake.

In contrast, the highest intake of plant-based oils such as corn, olive and rapeseed was associated with a 16 per cent reduced risk of dying, compared with people with the lowest intake.

The researchers suggested that every 10g per day increase in plant-based oil intake was associated with an 11 per cent lower risk of cancer death and a 6 per cent lower risk of heart disease death.

Meanwhile, a higher intake of butter was associated with a 12 per cent higher cancer death risk.

Substituting 10g per day of butter with an equivalent amount of plant-based oils was associated with an estimated 17 per cent reduction in death from any cause and a 17 per cent reduction in cancer death.

Writing in the journal JAMA Internal Medicine, the authors concluded that "higher intake of butter was associated with increased mortality, while higher plant-based oils intake was associated with lower mortality".

"Substituting butter with plant-based oils may confer substantial benefits for preventing premature deaths."

The data for the research was drawn from the US Nurses' Health Study, the Nurses' Health Study II and the Health Professionals Follow-up Study.

Researchers included those from Harvard Medical School in the US.

People's diets were assessed by food questionnaires every four years.