Selecting the proper food preparation method is equally important as selecting the right foods. Some foods require cooking while others are best whole and live.

Cooking methods affect nutrition of the foods you eat. There are several factors in cooking that affect the mutation value of the foods we eat. Improving your cooking methods can improve your health.

Cooking methods to avoid:

Grilling, Smoking, high temp fat frying and boiling.

Grilling is a very popular method of cooking in North America particularly in the summer. There are two major problems with grilling. First, most grilling involves fat in one form or another subjected to direct flame. This transforms the fat creating free radicals, which are known to be carcinogenic. Second, the fuels used to barbeque produce toxins that are transferred to the foods. Charcoal and wood are the worst offenders but even propane has its dangers.

Does charred meat really cause cancer?
The American Institute for Cancer Research doesn't mince its words. ‘Cancer researchers have found that grilling ... causes ‘muscle meats' (red meat, poultry and fish) to produce cancer compounds.'

Another cancer-causing substance forms when fat from meat, poultry or fish drips onto hot coals or wood and then, via smoke and flare-ups, is deposited onto the food above. These carcinogens are called PAHs or polycyclic aromatic hydrocarbons.

Some years back there was some confusion about barbecued foods containing a cancer-causing substance called benzo(a)pyrene. Studies showed that the cooking temperature, type of fuel used, and the fat content of the meat all affect the amount of benzo(a)pyrene that is formed. The most benzo(a)pyrene is the result of

charcoal grilling and gas grilling, when the gas flame is below the meat

grilling closer to the heat source

grilling meats with more fat

grilling for a long period of time.

Smoking:

Smoked meat is contaminated with polycyclic aromatic hydrocarbons, another carcinogen created when fat from meat drips onto hot coals and sends smoke back up into the meat.  In addition, cooking meat over charcoal emits air-polluting compounds including hydrocarbons, furans, steroids, and pesticide residues.

High temp fat frying

Ok, this will be a hard one for some, but we would not have your better interests at heart if we held back on the truth. We believe that frying and deep-frying are major causes of cancer - and there is plenty of scientific evidence to support this.

As you consider the following, may we again remind you that you do not have to give up anything - you only have to switch to using better alternatives. Whatever you have fried in the past can be baked and, because your taste buds will not be coated in oil, your food will taste so much better - especially if you bake at a temperature not exceeding 160C- 320F. Whatever you have sautéed in the past can be sautéed in cold processed/cold pressed sesame oil provided you do so at a low temperature

Frying - Be Warned?

What happens in frying? Temperatures up to 600-700 degrees F. may be obtained. If fried foods become burned or scorched, temperatures up to 1000 or 1100 degrees F. may have been reached. At these temperatures ``cis'' fatty acids are converted to ``trans'' fatty acids . . . in other words, the unsaturated fats behave as if they were saturated. Thus, fried foods are more likely than un-fried foods to increase the likelihood of hardening of the arteries. When fat is reheated to frying temperatures the second time, as in a deep fryer [or a popcorn vendor], the fat is more likely to develop the cancer producing agent acrolein.' (Dr Agatha Thrash, Nutrition for Vegetarians, p. 46)

The dangers to health of frying and deep-frying result from rapid oxidation and other chemical changes that take place when oils are subjected to high temperature in the presence of light and oxygen.
First, antioxidants in the oil (vitamin E and carotene) are used up.
Then, frying and deep-frying produce free radicals that start chain reactions in oil molecules.

Under these conditions, many chemical changes take place in oils. Frying and deep-frying produce some trans- fatty acids. These are the least harmful of the altered molecules produced by these processes.
Other oxidation products are far more toxic than trans- fatty acids.
Scores of unnatural breakdown, dimer, and polymer products with unknown effects on health are produced by frying and deep-frying.

Frying with oils once will not kill us, and so [this practice] seems harmless. Our body copes with toxic substances. But over 10, 20, or 30 years, our cells accumulate altered and toxic products for which they have not evolved efficient detoxifying mechanisms. The altered and toxic substances interfere with our body's life chemistry, our `bio-chemistry'. Cells then degenerate, and these degenerative processes manifest as degenerative diseases. (Udo Erasmus, Fats that Heal, Fats that Kill, pg. 125,126)

Boiling:

Boiling vegetables impairs anti-cancer properties

The anti-cancer properties of Brassica vegetables, namely broccoli, cabbage, cauliflower and Brussels sprouts, are well-known. However, boiling such vegetables severely impairs their potential health benefits, as a new UK study has reported.

Researchers from Warwick University purchased a selection of Brassica vegetables and evaluated the impact of different storage and different cooking methods on concentrations of glucosinolates. These are constituents of Brassica vegetables which are metabolised in the body to become substances known as isothiocyanates. These substances are thought to reduce the risk of some cancers.

The results showed that boiling the vegetables for 30 minutes reduced levels of glucosinolates by 58% to 77%, depending upon the vegetable. Steaming, stir frying or microwaving the vegetables had a negligible effect on levels of glucosinolates. Storing vegetables at ambient or refrigeration temperatures resulted in minor losses of glucosinolates. Freezing had a more severe impact, due to the thawing process.

It was concluded that people should avoid boiling vegetables in order to gain the maximum nutritional benefits (although 30 minutes seems a long time to boil vegetables!)

For more information, see
Song & Thornalley (2007). Effect of storage, processing and cooking on glucosinolate content of Brassica vegetables. Food Chemistry and Toxicology, Vol 45, pg 216-24.

The effect of different cooking methods on folate retention in various foods that are amongst the major contributors to folate intake in the UK diet

Abstract:

Folate intake is strongly influenced by various methods of cooking that can degrade the natural forms of the vitamin in foods. The aim of the present study was to determine the effect of different cooking methods on folate retention in various foods that contribute to folate intake in the UK diet. Typical purchasing and cooking practices of representative food folate sources were determined from a questionnaire survey of local shoppers (n 100). Total folate was determined by microbiological assay (Lactobacillus casei NCIMB 10463) following thermal extraction and tri-enzyme (-amylase, protease and conjugase) treatment in raw foods and after typical methods of cooking. Boiling for typical time periods resulted in only 49 % retention of folate in spinach (191·8 and 94·4 g/100 g for raw and boiled spinach respectively; P<0·005), and only 44 % in broccoli (177·1 and 77·0 g/100 g for raw and boiled broccoli respectively, P<0·0001). Steaming of spinach or broccoli, in contrast, resulted in no significant decrease in folate content, even for the maximum steaming periods of 4·5 min (spinach) and 15·0 min (broccoli). Prolonged grilling of beef for the maximum period of 16·0 min did not result in a significant decrease in folate content (54·3 and 51·5 g/100 g for raw and grilled beef respectively). Compared with raw values, boiling of whole potatoes (skin and flesh) for 60·0 min did not result in a significant change in folate content (125·1 and 102·8 g/100 g for raw and boiled potato respectively), nor was there any effect on folate retention whether or not skin was retained during boiling. These current results show that the retention of folate in various foods is highly dependent both on the food in question and the method of cooking. Thus, public health efforts to increase folate intake in order to improve folate status should incorporate practical advice on cooking.

Authors: McKillop D.J.; Pentieva K.*; Daly D.; McPartlin J.M.; Hughes J.; Strain J.J.1; Scott J.M.1; McNulty

Source: British Journal of Nutrition, Volume 88, Number 6, December 2002 , pp. 681-688(8)

Publisher: CABI Publishing