Customers who are involved in suspected food poisoning incidents in a restaurant should keep any leftover food, and their vomit and feces as evidence, Beijing health authorities have suggested.

The capital has a high incidence of microbial and mass food poisoning in summer and fall, said Cai Changjing, media officer of Beijing Health Inspection Institute on Monday.

The institute has published a set of guidelines on its website, giving suggestions on how to deal with a food poisoning incident, he told the Global Times.

"Customers should keep the restaurant receipt, and then we'll know which dishes in which restaurants have problems," Cai said.

"We also suggest people keep any leftovers, or vomit and feces as evidence," he noted.

Since the end of July, more than 2,000 cases of infectious diarrhea have been reported in the city, according to the Beijing News.

Li Na, 29, a resident in Beijing, said the institute's suggestion is useful but she feels it will be hard to implement.

"It's disgusting. I'd rather take some pills at home than collect the vomit as proof," she said.

"If the poisoning is serious, I'll just go to the hospital and let the doctor decide whether to keep these things," said Li.

Cai said that they also required restaurants not to cook wild vegetables they picked by themselves or those provided by customers, who then request the restaurant to cook them. 

"Not everyone can discern what a poisonous vegetable is," he said.

Liu Yanping, an employee of a restaurant in Changping district, told the Global Times that their boss had informed employees not to cook wild vegetables several times recently.

"We only cook those we recognise for fear of food poisoning incidents," she said.

A warning against mushroom poisoning was released by the institute on August 2 after 50 people in Shaanxi Province were poisoned in one month from eating poisonous mushrooms they had picked themselves.

Seven of them died in July, the Xinhua News Agency reported on August 3.