A rise in consumption of fizzy drinks could be to blame for some cancers of the gullet, research suggests.
There are health concerns about fizzy drinks
A team from India's Tata Memorial Hospital found consumption of carbonated drinks had increased five-fold in the US in the last 50 years.
They linked this to a six-fold increase in oesophageal cancer in white men - who consume the most fizzy drinks.
However, other scientists have questioned whether a link exists, and called for more research.
The Indian team found the same trend in UK and Australia, where fizzy drink consumption has also increased.
In the UK 7,200 people a year are diagnosed with gullet cancer - up 65% in the last 30 years.
But in countries like China and Japan, where the fizzy drinks craze has been much slower to
catch on, there was no rise in cancers affecting the oesophagus.
Researcher Dr Mohandas Mallath said; "The surprisingly strong correlation demonstrates the impact of diet patterns on health trends.
"As the rates may continue to rise for another 20 years, we believe that more epidemiological studies are urgently required to establish the true association."
Lee Kaplan, of Massachusetts General Hospital, stressed that the research in no way proved that consuming fizzy drinks caused gullet cancer - it was just pointing out a possible association.
He added that people who drink large amounts of carbonated drinks may have other
lifestyle factors which lead to cancer, such as being overweight.
However, research suggests that carbonated drinks cause the stomach to distend, which makes it more likely that its contents will flow back into the oesophagus.
Because the stomach contents tend to be acidic, they irritate the lining of the oesophagus - a phenomenon which has been linked to the development of cancer.
Dr John Toy, Cancer Research UK's Medical Director, says: "The increase in incidence of oesophageal cancer in recent years is alarming and somewhat puzzling.
"Reflux of the acidic gastric juices from the stomach into the oesophagus is a suspected culprit.
"People who are obese are more prone to this reflux and they have an increased risk of cancer.
"Carbonated drinks cause burping and some reflux. These drinks are also acidic and will bathe the lining of the oesophagus as they are swallowed.
"This retrospective association between diet and cancer is plausible but needs careful further research."
Richard Laming, of the British Soft Drink Association, said: "The author of the new study has only compared soft drink consumption data with an increase in a very rare type of cancer.
"He has not looked at the consumption patterns of the people who actually develop this type of cancer.
"Cancer researchers who have done this type of work have not found a relationship between the two.
"Furthermore, over the last two decades, many different aspects of diet and lifestyle have changed.
"There is no scientific basis for singling out one food as a possible cause."
The findings were presented to a Digestive Disease Week conference of gastro-intestinal specialists in New Orleans.