Cooking and health
Food safety
Main article: Food safety
When heat is used in the preparation of food, it can kill or inactivate potentially harmful organisms, such as bacteria and viruses, as well as various parasites such as tapeworms and Toxoplasma gondii. Food poisoning and other illness from uncooked or poorly-prepared food may be caused by bacteria such as pathogenic strains of Escherichia coli, Salmonella typhimurium and Campylobacter, viruses such as noroviruses, and protozoa such as Entamoeba histolytica. Parasites may be introduced through salad, meat that is uncooked or done rare, and unboiled water.
The sterilizing effect of cooking will depend on temperature, cooking time, and technique used. However, some bacteria such as Clostridium botulinum or Bacillus cereus, can form spores that survive cooking, which then germinate and regrow after the food has cooled. It is therefore recommended that cooked food should not be reheated more than once to avoid repeated growths that allow the bacteria to proliferate to dangerous level.[12]
Cooking prevents many foodborne illnesses that would otherwise occur if the food was eaten raw. Cooking also increases the digestibility of some foods such as grains or lactose because most foods, when raw, are inedible, and some are poisonous. For example kidney beans are toxic when raw or improperly cooked, due to the presence of phytohaemagglutinin which can be inactivated after cooking for at least ten minutes at 100 °C.[13] Slow cookerhowever may not reach the desired temperature and cases of poisoning from red beans cooked in slow cooker have been reported.
Preparation, handling, and storage of food are other considerations in food safety. According to the USDA, the temperature range from 40°F to 140 °F, is the "Danger zone" where bacteria is likely to proliferate, food therefore should not be stored in this temperature range. Washing of hands and surfaces, and avoidance of cross-contamination are good practices in food safety.[14] Food prepared on plastic cutting boards may be less likely to harbor bacteria than wooden ones,[15] other research however suggested otherwise.[16] Washing and sanitizing cutting boards is highly recommended, especially after use with raw meat, poultry, or seafood. Hot water and soap followed by a rinse with an diluted antibacterial cleaner, or a trip through a dishwasher with a "sanitize" cycle, are effective methods for reducing the risk of illness due to contaminated cooking implements.[16]
Effects on nutritional content of food
See also: Raw foodism
Proponents of Raw foodism argue that cooking food increases the risk of some of the detrimental effects on food or health. They point out that the cooking of vegetables and fruit containing vitamin C both elutes the vitamin into the cooking water and degrades the vitamin through oxidation. Peeling vegetables can also substantially reduce the vitamin C content, especially in the case of potatoes where most vitamin C is in the skin.[17] However, research using an artificial gut has shown that in the specific case of carotenoids a greater proportion is absorbed from cooked vegetables than from raw vegetables.[11]
German research in 2003 showed significant benefits in reducing breast cancer risk when large amounts of raw vegetable matter are included in the diet. The authors attribute some of this effect to heat-labile phytonutrients.[18]Sulforaphane, which may be found in vegetables such as broccoli, has been shown to be protective against prostate cancer, however, much of it is destroyed when the vegetable is boiled.[19]
Cooking and carcinogens
In a human epidemiological analysis by Richard Doll and Richard Peto in 1981, diet was estimated to cause a certain percentage amount of cancers.[20] Some of these cancers may be caused by carcinogens in food generated during cooking process, although it is often difficult to identify the specific components in diet that serve to increase cancer risk. Many food, such as beef steak and broccoli, contain low concentrations of both carcinogens andanticarcinogens.[21]
Several studies published since 1990 indicate that cooking meat at high temperature creates heterocyclic amines (HCAs), which are thought to increase cancer risk in humans. Researchers at the National Cancer Institute found that human subjects who ate beef rare or medium-rare had less than one third the risk of stomach cancer than those who ate beef medium-well or well-done.[22] While eating meat raw may be the only way to avoid HCAs fully, the National Cancer Institute states that cooking meat below 212 °F (100 °C) creates "negligible amounts" of HCAs. Also, microwaving meat before cooking may reduce HCAs by 90%.[22] Nitrosamines, present in processed and cooked foods, have also been noted as being carcinogenic, being linked to colon cancer.
Research has shown that grilling, barbecuing and smoking meat and fish increases levels of carcinogenic Polycyclic aromatic hydrocarbons (PAH). In Europe, grilled meat and smoked fish generally only contribute a small proportion of dietary PAH intake since they are a minor component of diet – most intake comes from cereals, oils and fats.[23] However, in the US, grilled/barbecued meat is the second highest contributor of the mean daily intake ofbenzo[a]pyrene at 21% after ‘bread, cereal and grain’ at 29%.[23]
Baking, grilling or broiling food, especially starchy foods, until a toasted crust is formed generates significant concentrations of acrylamide, a possible carcinogen.[24]
Other health issues
Cooking dairy products may reduce a protective effect against colon cancer. Researchers at the University of Toronto suggest that ingesting uncooked or unpasteurized dairy products (see also Raw milk) may reduce the risk ofcolorectal cancer.[25] Mice and rats fed uncooked sucrose, casein, and beef tallow had one-third to one-fifth the incidence of microadenomas as the mice and rats fed the same ingredients cooked.[26][27] This claim, however, is contentious. According to the Food and Drug Administration of the United States, health benefits claimed by raw milk advocates do not exist. "The small quantities of antibodies in milk are not absorbed in the human intestinal tract," says Barbara Ingham, PhD, associate professor and extension food scientist at the University of Wisconsin-Madison. "There is no scientific evidence that raw milk contains an anti-arthritis factor or that it enhances resistance to other diseases."[28]
Heating sugars with proteins or fats can produce Advanced glycation end products ("glycotoxins").[29] These have been linked to ageing and health conditions such as diabetes and causing obesity.
Deep fried food in restaurants may contain high level of trans fat which is known to increase level of low-density lipoprotein that may increase risk of heart diseases and other conditions. However, many fast food chains have now switched to trans-fat-free alternatives for deep-frying.[30]
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