Plastic plates are a favourite of parents and picnic-goers the world over, but new research suggests that eating hot meals on melamine crockery could actually be harmful to health.

Taiwanese researchers have found that hot temperatures increase the amount of melamine we are exposed to - and this can increase the risk of kidney stones, the Daily Mail reported.

They studied two groups of people who ate piping hot noodle soup. One group ate from melamine bowls, the other from ceramic bowls.

Urine samples were collected before the meal, and every two hours for 12 hours following the meal.

Three weeks later, the volunteers consumed the same kind of soup but the type of bowl they used was reversed. Urine samples were collected again.

Total melamine levels in urine for 12 hours after eating the soup was 8.35 micrograms when the participants ate out of the melamine bowls versus about 1.3 micrograms when they ate out of ceramic bowls.

Lead researcher by Chia-Fang Wu, of Kaohsiung Medical University in Taiwan, said: "Melamine tableware may release large amounts of melamine when used to serve high-temperature foods."

He noted that both higher temperatures (from hot soups, for example) or more acidic foods can encourage melamine to contaminate food, especially in older or low-quality kitchenware.

But he added that the amount of melamine released into food and beverages from melamine tableware varies by brand, so the results of this study of one brand may not be generalised to other brands.

However the results suggest it is advisable to serve hot food on ceramic crockery, to be on the safe side.

They added that it`s not yet clear what effect all of this might have on human health. However, prior studies have linked chronic, low-dose melamine exposures to an increased risk for kidney stones in both children and adults, the researchers said.

Studies of melamine toxicity in animals indicate that ingestion can cause kidney stones, kidney damage and may induce cancer.

The study was published in the journal JAMA Internal Medicine.