Food Safety Focus (97th Issue, August 2014) – Food Safety Platform
Carcinogens in Food
Reported by Mr. Arthur YAU, Scientific Officer,
Risk Assessment Section, Centre for Food Safety
This is the last of a series of three articles on food, carcinogens and cancer.
As discussed in the first article, carcinogens are present in many commonly consumed foods. With careful handling, carcinogens can be reduced to a low level even though complete elimination may not be possible. Below are some common examples to illustrate how we can reduce the risks.
Aflatoxins
Aflatoxin contamination of foods is common worldwide. It is estimated that up to 25% of world food crops are affected by these potent carcinogens from moulds especially in hot and humid climate. Exposure to aflatoxins is mainly through consumption of contaminated foods like corn, peanuts, cereals, nuts and dried fruits. As aflatoxin contamination is widespread in cereal staples in many parts of the world, one will inevitably ingest low levels of aflatoxins. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has recommended that the intake of aflatoxins be reduced to as low as reasonably achievable (ALARA), which means that the current agricultural and manufacturing practices cannot completely prevent or remove these potent carcinogens from crops without rejecting a large portion of the commodities in the food supply.
The concept of ALARA can be illustrated by the Brazil nut example. JECFA has estimated that in theory, if there is no maximum level (ML) for Brazil nuts, the mean aflatoxins level would be 20 μg/kg with no rejection of Brazil nuts from the world market. However, with an ML of 20 μg/kg, the mean level would be 2.4 μg/kg with 11% rejection, whereas an ML of 4 μg/kg would result in 1.2 μg/kg mean level with 17% rejection.
Arsenic
Arsenic is a metal that exists both naturally and as a result of human activities, and its exposure is mainly through drinking water and food. Its inorganic forms are generally more of health concerns to humans than the organic forms. The arsenic level in food that originated from land is generally low with a notable exception: rice, which is particularly capable of accumulating arsenic from the soil and environment when compared with other crops. The arsenic level would be even higher when the soil is naturally high in arsenic or through contamination. It was reported that rice can accumulate up to 510 μg/kg of inorganic arsenic, while inorganic arsenic level in other foods do not usually exceed 100 μg/kg with mean value generally less than 30 μg/kg. Since rice is a local staple, it is inevitable that we ingest some arsenic through rice consumption as reported in the First Hong Kong Total Diet Study.
Alcohol, Chinese-style Salted Fish and Cured Meat Products
Alcoholic drinks are consumed by adults in many societies, even though alcoholic beverages are known to cause human cancers in many sites such as the oral cavity, pharynx, larynx, oesophagus, liver colorectum, and female breast.
N-nitroso compounds are formed during the processing of Chinese style salted fish and when cured meat products like ham and preserved sausages are consumed. The added nitrate in cured meat can inhibit toxin formation by Clostridium botulinum bacteria while imparting the distinctive reddish colour and flavour of cured meats. It is impractical to ban these foods solely because of their carcinogenic components.
Reduce Cancer Risk by Minimising Exposure to Carcinogens through Foods
Even though it is not possible to completely eliminate all carcinogens from food, there are various approaches in minimising the effect of carcinogens. For unavoidable contaminants like aflatoxins, the ALARA principle is the internationally accepted approach, taking into account the best practices in production of a particular crop and set a maximum level for the commodity accordingly. For food additives like nitrate in cured meats, maximum levels are set for their use with consideration of the minimum level to achieve the desired effect. Salt preserved foods like cured meat should only be consumed in moderation, especially so for Chinese-style salted fish. Consumption of alcoholic drinks is not recommended. Keeping the carcinogenic contaminants at reasonably low level, avoiding or only consuming in moderation of foods that contain carcinogens and maintaining a healthy lifestyle are among the viable options to reduce cancer risk.