Food reheating and cardiovascular health: Welcome back to “The Science Of Health”, ABP Live’s weekly health column. Last week, we discussed whether spinal cord injuries are irreversible, and discussed science advances that can cure spine injuries in the future. This week, we explain how reheating food and cooking food at high temperatures change its chemical constituents, and how the consumption of this food is linked to increased cardiovascular disease risk.
In today’s fast-paced world, people are often unable to consume freshly-cooked food, and reheat food due to their busy schedules. Not everyone knows that eating reheated food is linked with an increased risk of cardiovascular diseases. This is because reheating food changes its chemical constituents, and releases toxic substances.
Check ABP Live’s stories explaining the science behind various health phenomena, and the articles appearing in the weekly health column here.
Why repeated heating of food, especially oil, and cooking food at extremely high temperatures, are harmful
When vegetable oil used for cooking is repeatedly heated, lipid oxidation occurs, as a result of which the health benefits are deteriorated. Also, thermal oxidation leads to the production of new functional groups which can be hazardous to cardiovascular health. If one continuously consumes repeatedly heated oil for a prolonged period of time, their blood pressure and total cholesterol will increase. Also, vascular inflammation occurs. Certain vascular changes take place which lead to atherosclerosis, or the buildup of fats, cholesterol and plaque on the walls of the arteries.
Therefore, heated oils are dangerous and harmful due to the hazardous products generated as a result of lipid oxidation due to repeated heating.
Similarly, deep frying is a dangerous practice because cooking food at high temperatures produces toxic products such as trans-fatty acids and advanced glycation-end products, which are modifications of proteins or lipids that become non-enzymatically glycated (sugar gets added) and oxidised after contact with aldose sugars, which are sugars containing an aldehyde group. Acrylamide, a compound formed from sugars and an amino acid naturally found in food, can be formed when food is deep-fried. These products are called neo-formed contaminants or NFCs.
Any healthy food cooked at a high temperature will result in the production of NFCs. When the cooking temperature is high, NFCs are produced at a high rate.
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Trans fatty acids are considered the worst type of fat to eat because they increase low-density lipoprotein (LDL) cholesterol or bad cholesterol, and decrease high-density lipoprotein (HDL) cholesterol or good cholesterol, according to Mayo Clinic. This increases the risk of heart disease.
Increased levels of advanced glycation-end products increase inflammation and oxidative stress in the body, and increase the risk for Alzheimer’s disease, heart disease, diabetes, and renal failure.
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According to the British Heart Foundation, the products generated as a result of cooking food at high temperatures damage the blood vessels, increasing high blood pressure, and hardening the arteries.
“Fats are denatured when food is reheated. That is, polyunsaturated fatty acids (healthy fats) denature and become saturated and trans-saturated. This causes an increase in LDL cholesterol and triglycerides. This, in turn, causes plaques in healthy heart vessels,” Dr A Guru Prakash, Consultant, Interventional Cardiologist, Yashoda Hospitals, Hyderabad, told ABP Live.
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Another problem associated with the reheating of food is protein denaturation, as a result of which the nutritional value of proteins decreases. Carbohydrates can turn brown due to caramelisation when the food is reheated, or if food is heated at extremely high temperatures. Vitamins and antioxidants also degrade when the food is cooked at high temperatures. If food is reheated in plastic containers, toxic chemicals may be released into the food.
“Reheating food can alter its chemical constituents due to the effects of heat. Proteins may denature, losing their original structure and possibly affecting their nutritional value or texture. Carbohydrates can undergo caramelisation, turning sugars brown and changing flavour profiles. Fats may oxidise, potentially producing harmful compounds. Vitamins and antioxidants can degrade when exposed to high temperatures, leading to nutrient loss. Overheating or prolonged reheating can lead to the loss of heat-sensitive vitamins and antioxidants in food. These nutrients play a protective role in heart health, so their degradation can have negative effects. Additionally, reheating in plastic containers may release chemicals into the food,” Dr Naveen Bhamri, Senior Director & HOD, Interventional Cardiology, Max Super Specialty Hospital, Shalimar Bagh, told ABP Live.
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Protein denaturation will result in the release of free radicals, and the innermost layer of the heart (endothelium) will be damaged by free radicals, according to Dr Prakash.
Apart from the nutrient loss and formation of harmful compounds and oxidation by-products due to the reheating of food, and heating food at high temperatures, these practices also lead to bacterial growth, said Dr Bhamri. “Improper storage and reheating of food can promote bacterial growth, increasing the risk of foodborne illnesses. In severe cases, these infections can lead to inflammation and cardiovascular complications.”
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One must use mild reheating methods like reheating at lower power levels, or reheating on a stovetop in order to minimise nutrient loss and chemical changes.
Therefore, it is important to change the cooking process, and the temperature at which oil is heated, instead of solely changing the amount of oil used. Unhealthy oils must be placed by healthy oils, and overheating and frying must be avoided.
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