Man frying food in a pan

Cooking food at a high heat can be bad for a number of reasons (Image: GETTY)

When you cook your own food, it’s mostly unprocessed foods you’re eating, which makes it healthier.

But according to US-based medical doctor Dr Mike Hansen, there are four methods of cooking that pose a health risk, whether that come in the form of increasing cancer risk or making people more likely to gain weight.

1. Cooking at high heat

Heating foods to high temperatures can be bad for a few different reasons, said Dr Hansen. One of those is glycation.

Glycation occurs when heat causes glucose and fructose to bind to proteins, creating advanced glycation end products (AGEs).

In a video posted to his YouTube channel, Dr Hansen explained: “Fructose is worse than glucose when it comes to AGEs. In fact, fructose metabolism leads to seven times more oxidative stress compared to glucose.

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“AGEs can be found in many processed foods, which are often flash heated to kill bacterial contaminants.

“Recent research suggests that AGES are not as harmless as previously thought. They’re absorbed through the gut and into the bloodstream where they bind to receptors on liver cells called RAGEs.

“This binding drives a molecular signal that stops the burning of energy and promotes fat accumulation instead.”

Studies have shown high levels of RAGEs in teenagers are associated with obesity and blood vessel damage.

And a study involving 70,000 women found that those who consumed the most AGEs had a 30 percent increased risk of developing breast cancer.

Heating foods to high temperatures can also lead to the formation of trans fats, said Dr Hansen. He explained: “Trans fats are incredibly unhealthy and are not commonly found in real whole foods. But they can be easily formed when unsaturated fats are heated to high temperatures.

“When an unsaturated fat such as olive oil is heated past smoking point…the cis double bonds in the unsaturated fat end up turning into a trans bond, so a trans double bond, and that results in the formation of trans fats.”

Olive oil

Understanding the smoking point of different oils is important (Image: GETTY)

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Dr Hansen said this highlights the importance of understanding the smoking point of different oils, and how heating oils to high temperatures can result in the formation of trans fat.

Of all the oils, extra virgin olive oil has the lowest smoking point, making it the most susceptible to trans fat formation.

Experts say extra virgin olive oil has a smoke point of 210C.

“So just make sure if you’re cooking with oil, that you’re not going past that smoking point,” said Dr Hansen.

2. Flash heating

Flash heating can form 3-MCPD fatty acid esters, said Dr Hansen – a harmful by product that can be found in processed foods.

He said: “They’re formed when free fatty acids from fats react with chloride ions in salt during the process of flash heating at temperatures above 400 degrees Fahrenheit, 240 degrees Celsius.

“These 3-MCPD fatty acid esters have been shown to have toxic effects on the kidneys, the testicles, and it may also impact the liver and other organs.”

Meet on a BBQ

Marinating meat before cooking can reduce the formation of PAHs (Image: GETTY)

3. Non-stick cookware

Non-stick cookware is coated with a material called polytetrafluorethylene (PTFE) which is a type of polyfluoroalkyl substance (PFAS), said Dr Hansen.

He explained: “PFAS are a group of synthetic chemicals that are resistant to heat, water and oil, which makes them ideal for use.

“However when the non-stick coating on the cookware is heated to very high temperatures PFAS can then be released into the food that’s being cooked.

“This can result in the exposure of PFAS which have been shown to be carcinogenic and obesogenic.

“PFAS have been linked to certain types of cancer such as liver and testicular cancers, as well as colon cancer.”

Dr Hansen added it’s best to be aware of the potential dangers of non-stick cookware and know there are alternatives, like cast iron, stainless steel and ceramic.  

4. Grilling polycyclic aromatic hydrocarbons (PAHs)

PAHs are a group of chemical compounds that are formed during the cooking process, particularly when fat and juices from meat come into contact with high heat sources, such as flames and hot coals.

Dr Hansen said: “This can be done during grilling, barbecuing or smoking of meat. PAHs are also present in the smoke that’s produced in the cooking process, which can cling to the surface of the meat and can also be inhaled.

“Studies have suggested that consuming and inhaling PAHs may increase the risk of certain cancers including lung, breast, bladder and colon cancer.

“PAHs can be formed when organic matter such as wood or coal or oil is burned or subjected to high heat which can cause the release of chemicals that can bind to other substances to form PAHs.

“But the formation of PAHs during the cooking process is a particular concern because of the popularity of outdoor cooking methods during the summer.”

Dr Hansen advised there are several methods that can be used to reduce the formation of PAHs during cooking:

  • Marinating the meat before cooking
  • Using a lid on the grill or smoker to trap the smoke and reduce the amount of PAHs that come into contact with the meat
  • Choosing cooking methods that don’t involve high heat, such as baking or boiling

He added: “Consuming a well balanced diet that includes a variety of fruits, vegetables, whole intact grains, can also help to reduce the overall exposure to PAHs and even potentially counteract some of the effects of oxidative stress, especially if you’re consuming omega-3 fatty acids.” 

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