Thai consumers have once again been shaken by the recent news circulated earlier this month on social network channels which tells a story of the mother of a 19-year-old Malaysian girl who died of stomach cancer. According to the girl who shared the tragedy on her Facebook wall, her mother's regular consumption of leftover food was responsible for her death.
She claimed that leftover food, after reheated, releases chemicals which are detrimental to kidney and liver and can also cause cancer. This leaves readers of such a sad story feeling bewildered if food left from last night's meal can be a silent killer.
Gastroenterologist and hepatologist Dr Pitulak Aswakul urged Thai consumers not to be overly panicked about the news because the long-term consumption of leftover food and cancer risk is in fact not directly associated.
"The only concern when it comes to reheated leftover food is the possibility that the food might be contaminated with bacteria which is likely to cause diarrhoea," said Dr Pitulak.
Whether it's freshly-prepared dishes or leftovers, first, the doctor said it is important to understand red meats when cooked at high temperature or over 180C such as in frying or grilling release carcinogenic agents, a result of the change in some amino acids in the meat.
And therefore if these leftover meats are heated again at high temperature, of course it means in the long run consumers put themselves at higher risk of developing cancer because these cooked meats are likely to lead to cancer in the first place.
When leftover food is refrigerated, it stops the growth of bacteria in food, but only temporarily, said the gastroenterologist. But heating the food by means of microwave is notoriously known to not cook the food evenly given it does not render enough heat.
This means when we microwave the leftovers for the next meal, the heat doesn't kill the bacteria, which brings about contamination and certain gastrointestinal symptoms, especially diarrhoea.
In line with Dr Pitulak's explanation are recommendations by the World Health Organization (WHO) with regard to food safety and the use of microwave ovens. In a microwave, the rate of heating depends on the power rating of the oven and on the water content, density and amount of food being heated.
According to the WHO, in normal circumstances, microwave energy does not penetrate well in thicker pieces of food, and may produce uneven cooking. This is likely to cause a health risk if some parts of the food are not heated sufficiently to kill potentially dangerous micro-organisms.
So for safety reasons, food heated in a microwave oven should rest for several minutes after cooking is completed to allow the heat to distribute throughout the food, according to the WHO.
Due to the fact that Thais have a habit of not throwing away the remaining food but rather prefer to keep it for the next day, Dr Pitulak suggested that consumers not keep foods for more than 24 hours.
"This rule only applies to tropical countries like Thailand, for example, because weather like this is likely to quickly spoil the food. In some Western countries, on the contrary, we can leave food in room temperature and it is still good to eat even on the next day," said Dr Pitulak, adding that food that is cooked at temperatures lower than 180C such as boiling and steaming is less likely to cause cancer even if it's reheated.
Consumers should be extra cautious when it comes to seafood and poultry, said the specialist, because bacteria in said food such as Salmonella in duck and chicken can grow faster than that in any other kinds of food. Consequently, leftovers that contain seafood and poultry must not be stored for more than 24 hours.
But in all, to fix the root cause of this problem, Dr Pitulak recommended that consumers not prepare too much food for each meal so that there is nothing left over.
"Eating leftover food is common in every household," she said. "Even I myself do it sometimes. But it's best to cook a portion of food that can be finished in one sitting to reduce the risk of any foodborne illnesses that might be caused by contamination."
