Reader Boey San Fei wrote in to AskST: "Is it unhealthy and a cancer risk to eat bak zhang (rice dumplings) as they are cooked for two or more hours with plastic raffia string?"

Mind&Body editor Ng Wan Ching has the answer.

Although there are no studies on whether cooking with plastic raffia string could pose a danger to health, dietitians here advise using other materials.

Rice dumplings or bak zhang should not be cooked with raffia as this material is not made for cooking. Chemicals from the string might melt into the boiling water and be absorbed by the food, said Dr Lim Su Lin, chief dietitian at National University Hospital. Reed string made from plants or string/twine made from 100 per cent cotton should be used instead, she said.

Principal dietitian Bibi Chia at Raffles Diabetes and Endocrine Centre also recommends using food-safe meat string or cotton.

When it comes to the bak zhang ingredients, you might be surprised to hear that glutinous rice has a lower caloric and carbohydrate content than normal white rice.

However, ingredients such as fatty pork and salted egg yolk are high in sodium and fat, said Ms Chia.

The nutritional value of a typical bak zhang, made with glutinous rice, filled with fatty meat, chestnuts and chopped mushrooms, wrapped in leaves and steamed:

•Weight per serving: 185g

•Energy: 386.65 kcal

•Protein: 11.84g

•Total fat: 13.51g

•Saturated fat: 5.37g

•Dietary fibre: 4.63g

•Carbohydrate: 54.58g

•Cholesterol: 101.75mg

•Sodium: 680.8mg

Bak zhang can be made healthier by using ingredients with lower sodium and saturated fat levels, such as unpolished glutinous rice, beans, chestnuts and lean meat, said Ms Chia.