Lung cancer is a major killer
Commonly-used food additives may fuel the growth of lung cancers, a Korean study on animals has suggested.
Processed foods including meat, cheese, and drink contain inorganic phosphates.
Researchers fed mice with lung cancer a diet with similar percentages of phosphates to those in human food, and found tumour growth accelerated.
But UK experts stressed the findings reported in the American Journal of Respiratory and Critical Care Medicine may not be repeated in humans.
Phosphates are an essential nutrient for living organisms, and adding phosphates to food can improve its texture and ability to retain water.
But the study suggested that high levels of inorganic phosphates may be interfering with the body's cell signalling systems.
The researchers, from Seoul National University, studied mice bred to automatically develop lung tumours.
The animals were given a diet of either 0.5% or 1% phosphate, which the scientists suggested represented the levels in modern human diets.
After four weeks, lung tissue was analysed. Tumours from the 1% phosphate mice had grown faster.
Dr Myung-Haing Cho, who led the study, said: "Lung cancer is a disease of uncontrolled cell proliferation in lung tissue, and disruption of signalling pathways in those tissues can confer a normal cell with malignant properties.
"This study demonstrates that high intake of inorganic phosphates may strongly stimulate lung cancer development by altering those signalling pathways."
He said that phosphate levels in modern diets had risen even in recent years, perhaps reaching 1000mg a day in some cases.
"The average diet today is actually closer to the 1% diet and may actually exceed it," he said.
However, Professor Stephen Spiro, the deputy chairman of the British Lung Foundation, said that the case was far from being proven.
"Whilst this may be a relevant observation it has never been assessed in man, and any recent increase in high phosphate ingestion due to excessive phosphates in processed foodstuffs would be likely to take many years before they could affect tumour development in humans.
"This study does suggest that it may be worth while assessing phosphate ingestion in the modern diet; however, further study would be required to ascertain any link in humans."
A spokesman for the Food Standards Agency confirmed that phosphates were legally used in UK foods, but said it had not yet had the chance to assess the study.