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There is no doubt that cooking food adds physical and chemical benefits to it, facilitating mastication, improving digestion and increasing the absorption of various nutrients, not to mention the enhanced flavors that are incorporated into food.
Some cooking techniques, depending on the temperature used, can cause the formation of harmful substances, such as Maillard Reaction Products (MRPs).
This is especially true within high temperature cooking techniques.
In recent decades, high-heat cooking has become more popular and, as a result, the consumption of MRPs has increased considerably.
This article focuses on the impact of high temperature cooking and the effects of the resulting harmful substances on health.
For the purpose of this article, cooking methods can be divided into two groups, depending on the temperature ranges:
- Mild temperature cooking methods, such as Sous-vide, steaming, poaching, simmering, and boiling, are done at around 212F/100C or lower.
- Medium/High temperature cooking methods of 284F/140C or over, such as roasting (meat)/baking (wheat based products e.g. bread, cookies), grilling, broiling, frying/deep frying and stir frying.
Dangers of high heat cooking
High heat cooking methods produce Maillard reaction products (MRPs) giving them characteristic texture, taste and flavor.
The clear changes when you sear a steak, roast almonds, brew coffee or fry golden-brown potato chips, are just a small sample of the visible part of this reaction.
It is undisputable that foods that have undergone Maillard reaction taste and smell delicious.
However, the MRPs responsible for these properties also include a wide range of invisible molecules, some of which may have some health benefits (more studies are needed), while others have been proven to be harmful.
- Antioxidant, antimicrobial and antihypertensive properties from the Melanoidins. These compounds may also have beneficial effects on gut anaerobic bacteria, such as in the Bifidobacteria strains.
- Anti-oxidative properties from the Pronyl-lysine substance.
- Possible benefits in the immune system and in reducing toxicity levels from some nitrosamines
Most prevalent, harmful substances found in MRPs: (7)
- Acrylamide – toxic substance with potential mutagenic and carcinogenic properties. It is five times higher in MRPs-rich diets than in steamed food based diets. (8, 9, 10, 11)
- Hydroxymethylfurfural (HMF) – potentially carcinogenic in humans. It is 40 times higher in diets rich in MRPs than in steamed based diets. (12)
- Heterocyclic amines – include potent carcinogens (13)
- N-Carboxymethyllysine (CML) – associated with type 2 diabetes and cardiovascular diseases (14)
- Insulin resistance development, that can lead to or aggravate a type 2 diabetes condition
- Renal dysfunction
- Inflammation, by increasing the formation of pro-inflammatory cytokines, such as tumor necrosis factor-alpha
- Increased risk of developing cardiovascular diseases
- Increased production and accumulation of harmful Advanced Glycation End Products (AGEs) in the body. These substances cause inflammation and are associated with cataracts and age-related macular degeneration, damage to the kidney tissues, vascular complications in diabetics, atherogenesis, neurodegenerative diseases, such as Alzheimers and Parkinsons, loss of bone mass, and changes in DNA and RNA structure and function.
- Additionally, a MPRs-high diet can lead to:
– The destruction of an essential amino acid, the lysine
– The reduction in the absorption and digestibility of proteins (16, 5)
– The decrease in the bioavailability of minerals (e.g. iron, magnesium, calcium and phosphorus). (12)
Steamed based diets compared to high heat-treated diets, show the following differences: (17)
- Reduction of biomarkers associated with type 2 diabetes and cardiovascular diseases
- Higher concentration of Omega-3 in the blood
- Higher concentration of vitamins C and E in the blood
Additionally, a diet based on high temperature cooking methods significantly increases insulin resistance and can lead to an increase of blood cholesterol and triglycerides.
How to limit foods with harmful substances produced by high heat cooking?
To reduce the risk of developing insulin resistance and type 2 diabetes, and the production and accumulation of harmful AGEs in your body follow these steps:
- Choose low temperature cooking methods, such as sous-vide, steaming, poaching, simmering, and boiling.
- Limit high heat cooking methods (especially when cooking proteins) such as roasting (meat)/baking (wheat based products), grilling, broiling, frying/deep frying and stir frying.
- Decrease the consumption of high heat cooked foods, such as processed foods, ready-to-eat breakfast cereals, cookies/biscuits, grilled and fried foods and foods that involve high heat roasting/baking.
- Increase consumption of raw fruits, vegetables, high cocoa chocolate, nuts and seeds which contain antioxidants that counteract the destructive action of AGEs.