by admin-blog-kh | March 24, 2026 12:57 pm
The Indian Food Safety and Standards Act, 2006 (FSSAI) lays down laws for food manufacturing, storage, distribution, and sales. While the law is comprehensive, its enforcement remains weak, with food adulteration and unsafe practices common, particularly in street food. A major concern is the use of re-heated cooking oil, often done to reduce costs. Re-heating oil leads to the formation of harmful compounds like aldehydes, trans fats, and free radicals, which increase the risk of heart disease[5], cancer, and other illnesses. FSSAI recommends not re-heating oil more than three times and discarding oil with over 25% Total Polar Compounds (TPC). To reduce health risks, oil should be filtered after use, stored properly, and ideally reused only once. While economic factors drive re-use, being cautious about oil quality can protect against serious health problems linked to repeated consumption of re-heated oil.
The is a consolidated document with laws regarding food manufacturing, storage, distribution, import and sales. While the law is considered fairly comprehensive, it’s enforcement in India is highly questionable. Food adulteration and contamination are unacceptably common, especially in the street food category. This quick, cheap, easily accessible food is responsible for feeding a large portion of the working population. You might find yourself getting a samosa or bajji on the go from your local street vendor too. However, with the astronomical rise in grocery prices, the 20-rupee samosa or bajji should be treated with some suspicion. How can it be so cheap? How is the economics of this possible? This is not an attack on street vendors, but a call to think more critically about what we eat.
The Food Safety and Standard Authority of India[6] recommend not re-heating cooking oil more than 3 times. The government has introduced another parameter to gauge how safe oil is, called Total Polar Compound (TPC). TPC is formed during re-heating and is not fit for human consumption. If the TPC content of the reheated oil is greater than 25%, it should legally not be used for cooking. It is also recommended to filter the oil between uses to remove leftover food particles that could release toxic substances when reheated. Reheating cooking oil repeatedly is linked to various health problems including increased inflammation, cardiovascular disease, cancer and liver damage. Oil to be re-used should also not be stored for too long between uses – It tends to go rancid quickly. If the oil starts foaming, has a bad smell, or becomes thick and murky when reheated, it should be thrown away.
In general, nutritionists always recommend that you don’t re-heat cooking oil at all[8]. Use a minimal amount for frying in a small pan and throw away the leftover oil when finished. However, we must acknowledge the constraints of the current economy – With sky high oil prices, most middle-class families feel that they cannot afford to throw away oil after a single use. Let us look at what happens to oil when re-heated to understand if it’s worth the risk.
Heating oil results in an oxidation reaction, i.e. oxygen combines with the hydrocarbons in the oil. Reheating vegetable oils or even heating it to very high temperatures for long periods of time, releases a higher concentration of aldehydes, hydroxy-trans-4-nominal (HNE) and free radicals. These are toxic to the body, due to their unstable nature. They contribute to cell damage and increased inflammation, contributing to conditions like Cancer, Heart disease, Alzheimer’s disease, Dementia and Parkinson’s disease. Re-heating cooking oil also increases the amount of trans fats and LDL Cholesterol (the bad cholesterol) in the fried food[9]. Reheated oil is also more acidic, taking a toll on the digestive system.
Re-heating cooking oil to very high temperatures for long periods of time is even more harmful because it increases the speed at which these reactions happen. Storage between uses is also important. If the oil to be re-used isn’t first filtered and then stored in a cool, dry place, it is much more likely to turn rancid.
Consuming re-heated cooking oil is terrible for your health. The toxic chemicals produced during re-heating increase inflammation and cell damage in the body. The free radicals wreak havoc on the system, damaging important internal structures. The re-heated oil can even damage cell DNA, causing cancer. The excess trans fats and PUFA clog the arteries and cause heart disease. The risk of Alzheimer’s disease, Parkinson’s disease, stroke, kidney disease and liver damage also increases the more re-heated oil you consume.
According to nutritional experts, oil should not be re-heated. However, since we do not live in an ideal world, let’s talk about what can be done with used oil, mitigating the impact it would have on your health. First of all, never re-use oil that doesn’t have a high smoke point. If you fry foods in coconut oil or olive oil, do not re-use the oil at all. Refined sunflower oil or avocado oil have higher smoke points and can be saved for re-use. However, if you have heated it above its smoke point for a long time, and it has started to turn dark in colour, it is safest to throw it away.
The oil stored for re-use should also not have any visible particles of food in it. Let the oil cool down to room temperature and filter it through a strainer or fine cheesecloth lined with a coffee filter or multiple paper towels. The filtered oil should be stored in an airtight container in a cool, dry place. Oil stored for re-use should only be reused once, within 1 to 2 days from the first use. Even while following these good practices, you should always smell the oil before you actually fry anything in it. If the re-heated oil smells bad or gives off the smell of the food cooked in it the first time, just throw it away.
Making informed choices about cooking practices can significantly reduce the risk of long-term health problems. Being mindful about how often cooking oil is reused and following safe food preparation habits can help protect your heart and overall well-being[10]. Kauvery Hospital, with experienced specialists and advanced healthcare services across Chennai, Hosur, Salem, Tirunelveli, and Trichy, is committed to promoting healthier lifestyles through expert guidance, preventive care, and comprehensive medical support.
Is it safe to reuse cooking oil at home?
Reusing cooking oil occasionally may be safe if done correctly, but repeated reheating increases harmful compounds like trans fats and free radicals, which can damage health over time.
How many times can cooking oil be reused safely?
According to FSSAI, cooking oil should not be reheated more than three times. However, for better health, it is safer to reuse oil only once and avoid repeated heating.
What happens when cooking oil is reheated multiple times?
Reheating oil causes oxidation, producing toxic substances like aldehydes and free radicals. These compounds increase inflammation and may raise the risk of heart disease, cancer, and other chronic conditions.
What are Total Polar Compounds (TPC) in cooking oil?
TPC are harmful compounds formed when oil is heated repeatedly. If TPC levels exceed 25%, the oil is unsafe for consumption and should be discarded.
What are the health risks of consuming reheated cooking oil?
Regular consumption of reheated oil can lead to increased cholesterol levels, heart disease, inflammation, digestive issues, liver damage, and a higher risk of cancer.
How can I tell if cooking oil is no longer safe to use?
Oil that smells bad, foams, becomes thick, dark, or murky, or produces excessive smoke should not be reused, as these are signs of degradation and toxicity.
Which oils should never be reused after cooking?
Oils with low smoke points, such as olive oil and coconut oil, should not be reused for frying as they break down quickly and form harmful compounds.
How should used cooking oil be stored safely?
Allow oil to cool, filter out food particles, and store it in an airtight container in a cool, dry place. Use it within 1–2 days to reduce the risk of rancidity.
Does reheated oil increase the risk of heart disease?
Yes, reheated oil increases trans fats and bad cholesterol (LDL), which can clog arteries and significantly raise the risk of cardiovascular diseases.
Can reheated cooking oil cause cancer?
Repeatedly reheated oil produces carcinogenic compounds like aldehydes, which may damage cells and increase long-term cancer risk when consumed frequently.
Is reheated oil more harmful than fresh oil?
Yes, reheated oil contains more toxic by-products compared to fresh oil, making it significantly less safe for regular consumption.
What is the safest way to use cooking oil at home?
Use minimal oil for cooking, avoid deep frying frequently, do not overheat oil, and discard leftover oil whenever possible to reduce health risks.
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