"When we examined the reports, we found many had borderline or no statistical significance," said Dr Jonathan Schoenfeld of the Harvard School of Public Health in Boston.
Schoenfeld and colleagues say trials have repeatedly failed to find effects for observational studies which had initially linked various foods to cancer, 'The Observer' reported.
Initial studies have often triggered public debates "rife with emotional and sensational rhetoric that can subject the general public to increased anxiety and contradictory advice".
Recent reports have linked colouring in fizzy drinks, low-fat salad dressing, burnt toast and tea to elevated cancer risk.
The cancer risks involved in excess alcohol consumption are not disputed by scientists, but other links have been less easy to substantiate.
To examine the implications of these reports, researchers selected ingredients at random from the Boston Cooking-School Cook Book.
The 40 foods that had been linked to cancer risks included flour, coffee, butter, olives, sugar, bread and salt, tomatoes, lemon, onion, celery, carrot and lamb, together with more unusual ingredients, including lobster, tripe, veal, mace, cinnamon and mustard, the report said.
"We found that, if we took one individual study that finds a link with cancer, it was very often difficult to repeat that in other studies. People need to know whether a study linking a food to cancer risk is backed up before jumping to conclusions," said Schoenfeld.
The study was published in the American Journal of Clinical Nutrition.
