The British Journal of Cancer states that during the frying process protein- rich foods like meat, fish and eggs form mutagenic and carcinogenic heterocyclic amines (HCAs)  and particularly when temperatures are very high. These chemical compounds have been proved to cause malignant tumors in the colons and breasts of mice and rats and are considered possible carcinogens to humans.  Some studies including (Phillips 3513-3522) and Demirer (2344-2348) have associated consumption of fried eggs and potatoes to cancer.

Frying food oxidizes the molecules, resulting in free radicals (unstable molecules that have one ‘free,’ unpaired, electron, which make them search for other molecules to bond to or displace) that have the potential to wreak havoc in the body. Antioxidants can be useful here to counteract free radicals (by serving as convenient binding agents that neutralize the free radicals before they react to endogenous molecules in an unhealthy way). That’s why traditionally herbs and spices were used in grilled/cooked foods such as rosemary with steak.

According to the American Cancer Society, when starchy foods such as potatoes are cooked at high temperatures of above 250° Fa chemical reaction between certain sugars and amino acid (asparagine) occurs forming acrylamide (a chemical commonly used for industrial purposes). According to research acrylamide has been found to increase the risk of several types of cancer in mice and rats which indicates a possible risk of cancer to humans. Polycyclic aromatic hydrocarbons (PAHs) are compounds formed from the incomplete burning of organic matter and advanced glycation end products (AGEs) form when foods are charred.

Therefore fried foods contain dangerous chemical compounds that contain mutagens and carcinogens that have been linked to various types of cancer. They raise low-density lipoprotein (LDL) and lower high-density lipoprotein (HDL), predisposing one to clogged and hardened arteries (atherosclerosis), and coupled with their high sodium levels heart disease and stroke become an imminent danger. Consumers are also at risk of kidney problems and those with impaired kidney function are unable to filter out the harmful compounds in fried food. Research has also confirmed that fried food consumption predisposes one to diabetes, Alzheimer’s and obesity.

The safety, calorific density, and nutritional value of food varies with the characteristics of the food and method of cooking (from most to leastharmful):

Deep Frying

Though a popular method of cooking that produces delicious dishes. It is the least healthy method of cooking, and destroys most nutrients because of the high temperatures involved. Though oil can protect some nutrients like vitamin B and C, it adds calories, and dangerous compounds are formed in the process.  These foods have a higher calorific density and are harder to digest.

Roasting

 A dry heat method that involves an open flame, and is mainly used for meats, roots and bulb vegetables, temperatures of at least 300 °F are used. It enhances the flavor of food through caramelization (oxidation of sugar) and Maillard browning (chemical reaction between amino acids and sugars, resulting in brown color), and through this process harmful chemical compounds are formed.

Grilling

It ensures maximum nutrition without sacrificing flavor, requires minimal added fats, keeps meats and veggies juicy and tender. It is definitely a healthier option, but not everything about grilling is rosy. Some research suggests that regularly consuming charred, well-done meat may increase the risk of pancreatic cancer and breast cancer. Cooking with high heat can also create a chemical reaction between the fat and protein in meat, creating toxins linked to the imbalance of antioxidants in the body and inflammation, which can lead to an increased risk of cancer, diabetes, and cardiovascular disease.

Baking

Cooking temperatures are considerably higher than those steaming and boiling. Meaning vitamins and minerals can be lost. Cooking vegetables with skins intact minimizes the contact with air, therefore, reduces the loss of nutrients. Baking makes protein in meat and eggs easier to digest, and in the case of grains, it can increase the amount of vitamin B. Higher temperatures and prolonged baking times destroy more nutrients, so boiling and steaming are better alternatives for fruits and vegetables, and baking may only be used for meat and grain products. This method is not entirely safe, since chemical compounds are formed due to the high temperatures and prolonged cooking duration.

Boiling

Boiling is a quick and easy method of cooking and needs nothing but water and a touch of salt. But the high temperatures and a large volume of water dissolves and washes away water-soluble vitamins and 60 to 70 percent of minerals. Making it unsuitable for vegetables. Some research suggests boiling is a good method to preserve nutrients in some vegetables like broccoli, zucchini, and carrots, though sometimes the high temperatures lead to the formation of dangerous compounds.

Stir-frying

This method requires minimal oil, just enough to sear meat and vegetables and is a much healthier option when compared to deep frying due to the use of a small amount of oil. It’s suitable for small chunks of meat, grains like rice and quinoa, and veggies like bell peppers, snow peas, and carrots.

Poaching

Very similar to boiling though only a small amount of water and seasoning is needed. It basically means cooking food in a little hot water, just below boiling point. It may take slightly longer which some experts believe decreases nutrients, but is an excellent way to cook foods like fish and eggs.

Steaming

Anything from fresh vegetables to small chunks of meat can be steamed. It allows food to cook using the high temperature of steam, and without adding water, therefore retaining all the essential nutrients. There’s no need for fat to preserve moisture and a little seasoning can be added for taste. Research suggests it may be the best method to cook vegetables like broccoli to retain glucosinolates which inhibit the growth of cancer cells.

No Cooking/Raw Food

Health freaks have resulted to raw food since food in its original state has more vitamins, minerals, fiber and no additives. It is considered safe, because it is not exposed to heat to form dangerous chemical compounds, and is rich in antioxidants that eliminate toxic compounds from our bodies. But research has proven that though consuming raw foods may be beneficial, cooking may in some cases increase the availability of nutrients like lycopene and carotenoids. Cooking also kills microbes and other microorganisms which may cause disease. This essentially means that cooking foods like tomatoes, peppers, carrots, sweet potatoes and spinach makes them more valuable to the human body.

Eggs already have 210 milligrams of cholesterol before cooking, when boiled an egg has 77 calories and 90 when fried, fried eggs are linked to cancer due to the formation of HCAs though at lower levels as compared to meat, therefore poaching and boiling would be considered healthier preparation methods.  Fried potatoes are loaded with the chemical compound acrylamide that is quite toxic to the body; therefore one can opt for suitable  low-heat methods when preparing them.

Direct heat methods like frying, grilling, roasting and baking produce more chemical compounds as compared to low-heat methods like stewing, steaming and poaching, which are considered relatively safe and retain nutrients. They also make food more palatable and enhance the availability of nutrients like lycopene and carotenoids.

Works Cited

Cahill LE, Pan A, Chiuve SE, Sun Q, Willett WC, Hu FB and Rimm EB. Fried-food consumption and risk of type 2 diabetes and coronary artery disease: a prospective study in two cohorts of U.S. health professionals. Am J Clin Nutr 2014;100(2);667-674.

Demirer T, Icli F, Uzunalimoglu O, Kucuk O. Diet and stomach cancer incidence. A case-control study in Turkey. Cancer. 1990;65:2344–2348.

IARC, International Agency for Research on Cancer some naturally occurring substances: Food items and constituents, heterocyclic aromatic amines and mycotoxins IARC Monogr Eval Carcinog Risks Hum1993Lyon, France: IARC; Vol. 56.

Phillips RL. Role of life-style and dietary habits in risk of cancer among Seventh-day Adventists. Cancer Res.1975;35:3513–3522.

Sinha R, Kulldorff M, Curtin J, Brown CC, Alavanja MCR, Swanson CA. Fried, well-done red meat and risk of lung cancer in women (United States) Cancer Causes Control. 1998a;9:621–630.

Steineck G, Gerhardsson de Verdier M, Övervik E. The epidemiological evidence concerning intake of mutagenic activity from the fried surface and the risk of cancer cannot justify preventive measures. Eur J Cancer Prev.1993;2:293–300.

Steineck G, Hagman U, Gerhardsson M, Norell SE. Vitamin A supplements, fried foods, fat and urothelial cancer. A case-referent study in Stockholm, 1985–87. Int J Cancer. 1990;45:1006–1011.

 http://www.cancer.org/cancer

http://www.nature.com/bjc

https://www.nih.gov/