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Cooking oil is a staple food item in every household. While there are several types of cooking oil, vegetable oils are probably the most popular cooking oils in India. The most common among these include mustard oil, soybean oil, corn oil, sunflower oil, and safflower oil. Unfortunately, there are several safety issues plaguing cooking oils, and one of the biggest is that of rancidity.
Rancidity is a general term used to denote unpleasant odours and flavours in foods as a result of deterioration in the fat or oil component. The main reasons why oils go rancid in Indian households are improper storage and excessive heating during cooking. Every cooking oil is susceptible to oxidation in the presence of heat, air and light. When oils are heated or stored for a long time, they start getting rancid. Some oils may go rancid just by being exposed to sunlight. When oil goes rancid, it smells and tastes bad, but those problems are minor compared to safety issues linked to consuming rancid oil.
Rancidity of cooking oil is one of the biggest threats to people's health in India, and we need to be aware of the risks associated with it, as well as the simple steps required to minimise these health risks.
Perhaps the biggest safety issue arising out of using rancid cooking oil is the fact that we in India tend to use polyunsaturated fatty acids or PUFA-rich oils such as sunflower oil to cook, and heating causes the PUFAs in the oil to produce toxic trans fats, among other dangerous chemicals. I have talked about the safety issues associated with trans fats in an earlier article. Rancid PUFA and trans fats are toxic, and should ideally not be in our diets at all.
A 2015 article in the Journal of Drug Discovery and Therapeutics noted that when oils like sunflower and safflower oil are oxidized by exposure to light (oxidative rancidity), the chemicals that form are associated with increased cancer risk.
I believe that rancid vegetable oils are an important reason for the increased rates of cancer and other lifestyle diseases in India in recent decades. Prior to about 1960, Indians used the relatively inert and safe ghee or coconut oil for high heat cooking. Other vegetable oils were used for pickling, added to chutneys and otherwise used in food raw or for low heat cooking. The explosion of cheap vegetable oils for cooking has happened mostly in the last 60 years. Some vegetable oils like extra virgin olive oil, almond oil and sunflower oil are excellent sources of Vitamin E. This is evident from the fact that just one tablespoon of extra-virgin olive oil has 2 milligrams of Vitamin E, which is equal to 10 percent of our daily requirement.
Prior to about 1960, Indians used the relatively inert and safe ghee or coconut oil for high heat cooking. Other vegetable oils were used for pickling, added to chutneys and otherwise used in food raw or for low heat cooking.
Vitamin E is an excellent source of antioxidants which help to rid the body of free radicals that have been linked to various health issues. However, consuming rancid oils may actually reduce the body's Vitamin E levels. A study published in the Journal of Aquaculture Research reported that blood levels of a-tacopherol acetate (a type of Vitamin E) rapidly increased in American catfish when the fish were given extra a-tacopherol. However, when the same fish were given rancid oils to eat, these levels significantly dropped.
There are several simple, yet effective methods to prevent oil from going rancid. Buying oil in tinted bottles prevents exposure to light. This is especially important in the case of plant based oils. The 2015 article also recommends using palm oil, butter, olive oil or coconut oil while frying (something Indians do all the time), as they help to maintain a better PUFA balance. I agree with this recommendation, except for the olive oil. Olive oil is not suitable for high heat cooking as it does have significant PUFA content.
Oils that are rich in PUFA are better consumed raw or used in very light-heat cooking. It is not advisable to use these oils for high heat cooking practices common in India such as tadka or deep frying.
Oils that are rich in PUFA are better consumed raw or used in very light-heat cooking. It is not advisable to use these oils for high heat cooking practices common in India such as tadka or deep frying.
Oils primarily comprising saturated fatty acids and/or monounsaturated fatty acids (MUFAs), such as coconut oil, palm kernel oil, ghee or clarified butter, have a longer shelf life than oils rich in polyunsaturated fatty acids (PUFAs). Not using the same oil multiple times, storing it in a cool, dry place, and replacing the cap on the bottle properly after using it also goes a long way in preventing oils from going rancid.
Rancidity of cooking oil is one of the biggest threats to people's health in India, and we need to be aware of the risks associated with it, as well as the simple steps required to minimise these health risks.