Reusing oil - why is it dangerous for your health?

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One litre of oil costs Rs 3.60 more since this Sunday. Consequently, more and more people might be tempted to reuse oil when cooking. But can reusing the same oil again lead to health problems? We decided to find out.




Oil is a very essential part of cooking. It is usually the first step of cooking. Place a pan on the gas and pour some oil into it. Since it is so frequently used, often people tend to reuse it several times. But is this practice safe? Can it lead to health problems? Let’s find out.

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What happens when you use the same oil for deep frying again and again?

The problem with reusing oil is that it can create free radicals which cause ailments in the long run. According to diet consultant Nisha Goolub, ‘Free radicals attach themselves to healthy cells and lead to diseases. These free radicals can be carcinogenic i.e. can cause cancer and also atherosclerosis which can lead to increase in bad cholesterol levels, blocking the arteries.’

Some other potential health risks of reusing oil include:

  • Acidity
  • Heart disease
  • Alzheimer’s and Parkinson’s disease
  • Irritable throat (due to inhalation)

How many times can one reuse oil?

Says nutritionist Priya Mauloo, ‘There is no set number to how many times one can reuse the oil as it depends on factors like which oil is used, how long the oil was heated, was it used for deep frying or shallow frying, what type of food was cooked in it etc…’

Though using a fresh batch every time is good, it is not really practical. But if done correctly, one can reduce the risk of negative effects that reused oil may pose. Priya lists a few pointers to help you reuse oil safely.

  • Make sure the leftover oil from cooking or frying is cooled down and then transferred into an airtight container through a strainer/cheesecloth. This will remove any food particles in the oil as they spoil the oil much sooner than expected.
  • Make sure you check the oil each time before reusing for the colour and thickness. If it’s dark in colour and is greasy/sticky than usual it is time to change the oil.
  • Also, if the oil is smokey on heating much before than expected, you need to discard this batch as it may have accumulated HNE which is a toxic substance that has been associated with a number of diseases including Parkinson’s, Alzheimer’s, stroke, liver disease, etc.
  • Another thing to remember is that not all oils are same. Some of them have a high smoke point i.e. they can be used for frying, deep frying. Basically they do not break down at high temperatures. Such oils include sunflower, safflower, soybean, rice bran, peanut, sesame, mustard and canola oil. Oils which do not have a high smoke point such as olive oil should only be used for sautéing, nothing which will involve high temperatures. So make sure you do not use the wrong oil for cooking and definitely don’t reuse it for frying, etc.