Hidden Killers in Food


Mandy Lau, HK BioTek Nutritionist


Cancer is one of the major killers in Hong Kong. According to the most recent report from Hong Kong Cancer Registry of Hospital Authority, lung cancer and colorectum cancer are the top two common cancers in Hong Kong, with crude incident rate of over 60%. Generally speaking, cancer is mainly caused by undisciplined lifestyle, especially unhealthy dietary habits. Hidden “killers” can be found in food. This article would introduce several common cancer-causing substances in food and present some health tips to protect from cancer.


Cancer is a type of disorder happened in body cells. In normal body, cells would divide and multiply orderly under systematic control. For abnormal cells with damaged genes, they might multiply without regulation, leading to the formation of plague of damaged cells called tumour. If the tumour becomes invasive and spreads to other tissues, cancer will then be developed. Any substances that cause abnormal cell division at DNA level are called carcinogens. They can further divided into several types: physical (e.g. UV light and radiation), chemical (e.g. Lead) and biological (e.g. toxin of bacteria).


Carcinogen in food can be a naturally occurring component or formed during food processing and cooking. Some can be avoided in totality while some cannot. The table lists some common dietary carcinogens and their related cancers.


Common Dietary Carcinogens Source Genotoxicity/Related Cancer(s)
Acrylamide Potato chips, French fries, cakes, bread Chromosomal mutation
Alfatoxins Moldy peanuts, cereals, nuts Liver Cancer
Inorganic Arsenic Contaminated drinking water, white rice Skin and Lung Cancer
Heavy metals

(e.g. Cadmium, lead)

Leafy vegetables, shellfishes, contaminated water Kidney and Prostate Cancer
Alcohol Alcoholic beverages Oral cavity, Pharynx, Larynx,

Oesophagus and Liver Cancer

Polycyclic Aromatic

Hydrocarbons (PAHs)

Roasted meat Genotoxic
Nitrosamine Processed meat (e.g. sausage, ham, bacon) Stomach Cancer
Dioxins and polychlorinated biphenyl (PCBs) Fatty tissue of animals (e.g. fish) Increased risk for all cancers combined

Source: Centre for Food Safety


As you may observed, acrylamide and PAHs are formed under high heat. Deep frying or roasting are frequently used cooking method in fast food restaurants and junk food production. Besides, nitrate is added as preservatives in many popular processed meat we consumed so as to make the “fresh reddish colour”. As a result, nitrate could react to form carcinogenic nitrosamine. As illustrated above, unhealthy eating habits could definitely increase your exposure to carcinogens.


Knowing that diet is an important cancer-causing factor, you can reduce the risk by adjusting to a healthy lifestyle. World Health Organisation suggests some practical tips:

  • Maintain regular exercise (at least 30 minutes a day)
  • Consume adequate fruits and vegetables
  • Drink adequate amount of water (at least 8 cups of water a day)
  • Avoid processed meat, high-fat food and high-sodium food
  • Avoid cooking method involving intense heat (e.g. deep frying, roasting)
  • Avoid alcoholic drinks and smoking