New studies have discovered how a fatty acid found in palm oil affects the cancer genome, increasing the likelihood the disease will spread in human beings.
The spread of cancer, known as metastasis, is the main cause of death in patients with the disease. Researchers in the field say the vast majority of people with metastatic cancer can only be treated, but not cured.
The Institute for Research in Biomedicine (IRB) in Barcelona conducted a study on mice, finding that palmitic acid promoted metastasis in mouth and skin cancers.
Scientists suggest this process could be targeted with drugs or carefully designed eating plans in the future, but the team behind the work has put out a warning for patients putting themselves on diets in the absence of clinical trials.
According to the research, other fatty acids called oleic acid and linoleic acid found in foods such as olive oil and flaxseeds did not show the same effect.
"There is something very special about palmitic acid that makes it an extremely potent promoter of metastasis," Professor Salvador Aznar-Benitah said via The Guardian.
The research found that when palmitic acid was supplemented into the diet of mice, it not only contributed to metastasis but also exerted long-term effects on the genome.
However, the professor also claimed it was too early to tell what diet should be taken for patients with metastatic cancers.
"I think it is too early to determine which type of diet could be consumed by patients with metastatic cancer that would slow down the metastatic process," he said.
"That is a much more realistic approach in terms of a real therapy, that doesn't depend on whether a patient likes Nutella or pizza. Playing with diets is so complicated."
Prof Greg Hannon, director of the Cancer Research UK Cambridge Institute, praised the "rigorous and comprehensive" study into one of the most commonly used oils around the world.
"This is a rigorous and comprehensive study that suggests that exposure to a major constituent of palm oil durably changes the behaviour of cancer cells, making them more prone to progress from local to potentially lethal metastatic disease," he said.
"Given the prevalence of palm oil as an ingredient in processed foods, this study provides strong motivation for further study on how dietary choices influence the risk of tumour progression."
Made from the fruit pulp of the oil palm tree, palm oil plantations are grown in tropical regions in Indonesia, Malaysia, Colombia, New Guinea and Ghana.
According to Ethical Consumer, it is the most consumed vegetable oil on the planet, with 72 per cent of worldwide production being used in the food industry. A 2015 report by the Roundtable on Sustainable Palm Oil estimated worldwide use would more than double by 2030 and triple by 2050.
Palm oil is a cheap substitute for butter, meaning it is especially common in dough and baked foods. It is commonly found in everyday pantry items, such as margarine, Nutella and biscuits.