High Temperature Cooking - Burnt, barbequed, grilled, and deep-fried food

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High Temperature Cooking - Burnt, Barbequed, Grilled and Deep-fried Food

Posted: Oct 2007 (Return to the original web page from this print version)

Improper cooking methods can produce a lot of cancer-causing substances on the food. These include:

	Cooking Method	Carcinogenic Substances Produced
1.	Burnt or overheated food	Polycyclic aromatic hydrocarbons (PAHs)
2.	Barbecued / grilled food	Polycyclic aromatic hydrocarbons (PAHs), Heterocyclic amines (HCAs)
3.	Burnt food during broiling & pan-frying	Heterocyclic amines (HCAs, also called HAs)
4.	High temperature cooking of starchy plant products (e.g., frying, grilling, baking and roasting)	Toxic acrylamide

High temperature cooking can easily result in burnt food that contains carcinogens called PAHs. Photo: grilled corn (partly burnt).

1. Burnt or overheated food

If foods are overheated or burnt, a group of carcinogenic substances called polycyclic aromatic hydrocarbons (PAHs) are produced. PAHs represent a very large group of compounds. Chemically, they consist of fused aromatic rings made up of carbon and hydrogen atoms.

After being ingested, PAHs can be absorbed in the intestine and distributed to other organs through blood circulation.

Besides cancer-causing, PAH exposure is also associated with many adverse effects in laboratory animals, including reproductive toxicity, cardiovascular toxicity, bone marrow toxicity, immune system suppression, and liver toxicity.

Cooking Tips:

1.	Do not overcook food.

2.	Remove any burnt / charred portion before eating.

When fat from grilled meats falls down on flames or hot coals, cancer-causing PAHs are formed. Photo: grilled satae

It is advisable to avoid barbecued fatty meat. Photo: barbecued pork

2. Barbecued and grilled food

When fat from grilled meats falls down on flames or hot coals, cancer-causing PAHs (polycyclic aromatic hydrocarbons) are formed. These PAHs rise as vapour and permeate the meat. Heavy charring of meats also produces high concentrations of PAHs carcinogens, such as benzopyrene.

Some grilled chicken products may also contain a dangerous carcinogenic compound called PHIP, which is one type of heterocyclic amines (HCAs / HAs).

In September 2006, a doctor's group sued seven leading fast food chains in the US because their grilled chicken contained PHIP. According to the president of this group, even a grilled chicken salad would increase the risk of breast cancer, prostate cancer and other types of cancer. (Related News: September 28, 2006)

Cooking Tips:

1.	Avoid barbecuing or grilling, especially those over charcoal

2.	Remove the fatty portion of meat before barbecuing or grilling.

Burnt food from high temperature pan-frying contains carcinogens (HAs). Avoid burning the food by turning it frequently.

3. Burnt food during broiling and pan-frying

If the meats are burnt during broiling or pan-frying, cancer-causing chemicals called heterocyclic amines (HCAs or HAs) are formed.

Recent research indicates that heterocyclic amines (HCAs) are also created within muscle meats (e.g. beef, pork, fowl, and fish) during most types of high temperature cooking. Researchers have identified 17 different HCAs resulting from the cooking of muscle meats that may pose human cancer risk. (Related web page)

Cooking Tips:

1.	Use lower temperature in cooking.

2.	Turn the food frequently to avoid over-burning.

Potato crisps and French fries contain very high levels of toxic acrylamide.

Deep-fried crisps, wonton, spring rolls, and deep-fried Chinese dough sticks (i.e. 油條 / 油炸鬼) are coated with carcinogenic acrylamide.

Avoid deep-fried crispy vegetables, e.g. Japanese tempura or Italian fritto misto.

High temperature baking of bread results in toxic acrylamide. Do not eat the skin of bread.

4. High temperature frying, grilling and baking of starchy plant products

In a research conducted by the University of Stockholm and Sweden's National Food Administration, it was found that high levels of toxic acrylamide are formed in carbohydrate-rich plant products cooked at high temperatures in pan-frying, deep-frying, grilling, roasting and baking.

These products include common food such as potato chips, French fries, baked potatoes and certain bread. Other items with lower levels of acrylamide include maize crisps, biscuits, toast, breakfast cereals (baked / roasted), and coffee powder. (Related News: BBC, ENS - Apr 25, 2002)

The same results were not found in boiled products. Result highlights:

1.	An ordinary bag of crisps may contain acrylamide up to 500 times more than the maximum level allowed in drinking water by the World Health Organisation (WHO).

2.	French fries sold at Swedish franchises of US fast-food chains contained acrylamide t about 100 times the maximum level allowed in drinking water by the World Health Organisation (WHO).

Acrylamide has been shown to cause cancer in animals in previous studies where they were exposed to the chemical at high doses. Acrylamide is also known to cause nerve damages in both the central and peripheral nervous systems for people exposed to very high levels at work.

Scientists in the Swedish government estimated acrylamide could be responsible for several hundreds of the 45,000 cancer cases in the country each year, based on experiments in which rats were fed fried food.

Another study conducted in Italy found that a diet high in refined cereals, and bread in particular, is associated with an increased risk of renal cell carcinoma (RCC), the main type of kidney cancer. (Related News: Oct 20, 2006)

Cooking Tips:

1.	Use relatively low temperature cooking. These include steaming, boiling, poaching, stewing, casseroling, braising etc.

2.	Avoid potato crisps and French fries.

3.	Reduce the intake of toasted cereals or nuts.

4.	Do not eat the skin of bread.


Avoid high temperature baking of potato or other vegetables