Bak kwa remains a popular Chinese New Year snack despite its high calorie content. You can buy it, make your own with ready-made sauce and even order some made with Australian free-range pork.

But, this Chinese New Year, you have another reason to not overindulge in these barbecued pork slices as bak kwa and lup cheong (Chinese sausage), another processed food commonly eaten during this festive period, are now considered carcinogenic.

Last October, the World Health Organisation's (WHO) International Agency for Research on Cancer announced that it considers processed red meat a Category 1 cancer-causing substance.

"The scientific evidence linking the consumption of processed red meat with increased risk of cancer, especially colorectal cancer, is definite and conclusive," said Dr Wong Seng Weng, medical director and consultant medical oncologist at The Cancer Centre.

Choosing to go organic likely won't help in this area. The use of nitrate-containing chemical preservatives may also lead to carcinogen formation, said Dr Wong.

"It is a myth that non-chemical means of curing meats is safe as chemical reactions involving the inherent fat and protein content of the meat will also lead to carcinogen formation," he said.

Dr Wong added that the use of antibiotics in animal husbandry probably makes no difference to human cancer causation.

"The use of growth hormones is potentially problematic in theory, but this has never been scientifically proven to raise cancer risk in reality," said Dr Wong.

There is no safe limit for the consumption of processed red meat, though it won't harm you as much as smoking will.

Dr Wong said you do not have to abstain from bak kwa or processed red meat, but you should moderate your consumption as "the risk rises progressively with increased consumption".

"The WHO estimated that an average consumption of an extra 50g of processed red meat a day will raise the risk of developing colorectal cancer by 18 per cent. That is not a lot; only a few slices of bak kwa will touch 50g," he said.

That same report from the WHO also classified unprocessed red meat as a Category 2A carcinogen, which means it is considered probably carcinogenic.

Dr Wong said the report mentioned that high-heat methods of food preparation, like grilling and deep-frying, are more likely to lead to the formation of carcinogenic substances, compared with low-heat techniques like boiling and steaming.

"Processed red meat cooked by grilling would potentially be a double whammy," he concluded.