Patrons at a restaurant sample genetically modified rice in Hangzhou, capital of East China's Zhejiang province, on July 14. [Photo/CFP]

Every year, Wang Xiuqiong defies a particular norm in the name of tradition: She makes her own moon cakes. As summer comes to a close, supermarkets and other shops around China quickly fill up with the Chinese pastry around the Mid-Autumn Festival, which fell on Sept 19 this year. The holiday food is a popular gift for friends, family and colleagues.

But keeping with tradition can prove difficult, as Wang, a native of Beijing, soon found out. Soybean oil is Wang's secret ingredient in her moon cakes, but this year she learned that most soybean oil sold in supermarkets is genetically modified (GM). For Wang, that's a big no-no. The supermarket near her home used to have a shelf dedicated to non-GM soybean oil, but the shelf was removed several months ago. A clerk at the supermarket told Wang it's almost impossible to find non-GM soybean oil suppliers. Wang ended up using sunflower seed oil to make moon cakes this year, fearing health hazards from using GM soybean oil.

Wu Mei, an official in charge of data collection at the Beijing Municipal Bureau of Statistics, said it's quite hard to buy non-GM soybean oil in big cities, as only small oil manufacturing factories in rural areas produce it. "Over 90 percent of the soybean oil for sale in Beijing is genetically modified," she said.