Can stale oil cause health problems?

It hardly matters what type of oil has been used for frying any stuff, the used oil contains toxic substances and is known as Rancid. It may get decomposed with the progress of time and it will not offer any palatable test because of decomposition of such oil.
Stale oil containing Rancid may loose healthy properties such as antioxidants offering maintenance of good health.
Rancid foods are less nutritious since oxidation involved during the process would destroy healthy fats and the essential vitamins for the upkeep of sound health.
Moreover, the stale oil would accompany bad smells sometimes suggesting that the original composition of the oil has undergone transformation with the changed composition of the molecules of the oil, potentially causing health - hazards.
Stale oil may cause severe health - damage on its consistent use. A few are noted below -
1) It may cause indigestion because of lack of nutrient in it.
2) On prolonged usage of such oil, it may affect our lever because of its overworking.
3) It may affect our Lipid - profile. Stale oil would ultimately cause, high cholesterol, high transfat and low HDL- essential for maintenance our heart in healthy condition.
4) There could be excess surge of body weight due to poor metabolism of the body - system.
5) Rancid present in the stale oil may cause even cancer if used consistently.

All types of edible oils become stale or rancid, as they are technically called, if stored for a long time like 6 months to 1 year. In fact the vegetable oil qualities start degrading from 3 months itself. Their smell changes with that and are terms as rancid oils. They also get a change in their colour and are slightly thickened also. This is observed in nuts also like walnuts often get rancid with time. The rancid oils are known as spoiled oils also. First thing which happens is the taste of the oil is ruined and we do not feel to eat the dishes made up with rancid oils. Due to this transformation or degradation the oils lose some of their good properties. For example olive oils when become rancid, lose some of their antioxidant properties. The main reasons for the oils to become rancid are warm climate, sunlight or normal light and oxygen.

To preserve the oils for a long time they can be kept in refrigerator or in dark glass bottles and in shade so that they do not get rancid early. Research shows that in rancid oil, free radicals are produced which are not good for the health. They are linked to Alzheimer's disease and Diabetes. These radicals are carcinogenic in their character and also responsible for many other ailments including damage to arteries and creating digestive disorders. It is advised not to use the rancid oils for edible purposes.

All edible oils will have a shelf life. The shelf life depends based on the type of oil and storage conditions. Once the shelf-life period is crossed the oil will become rancid. This is also called stale oil. Even though the oil is fresh but you boiled it once and you want to use it again, the oil will be more dangerous for health. Repeatedly boiled oil is very bad for health. If the oil is exposed to sunlight, heat and open air for long it will lose its structure and transfats will increase.

The problems with the rancid oils are.
1. They lose their vitamins.
2. They also can develop potentially toxic compounds
3. Flavour will be lost.
4. The pungent smell will be developed. Some people may like this smell.
5. Trans fat will become more in the oil. It is difficult for our body to process these fats.
6. Antioxidants will reduce and hence it will be more unhealthy.
7. They may produce carcinogens and they many find long term problems like bad lever functioning and may lead to cancer also.

Always fresh vegetable oils are better and reboiling should be avoided. Refined oils are also not good for health.

Hello ma'am.

The oil contains unsaturated and polyunsaturated fats. It is because these fats allow the oil to be liquid at room temperature. Unsaturated fats have a carbon-carbon double bond in their structure. But these bonds can be broken by oxygen in the air by the process of oxidation. So if we forget to close the lid of the oil's bottle, the oil will be exposed to oxygen. This carbon-oxygen bond may lead to a number of products such as aldehyde, ketone and carboxylic acid. These products have a rancid odour and tastes. Also, heat accelerates these chemical processes and can make the oil go rancid very quickly. That is why cooking oil should be preserved in a dark place and it must be tightly capped.

Those oils that have more carbon-carbon double bonds would spoil more readily if they are exposed to heat, oxygen etc. Corn oil will spoil fastest, canola oil next and olive oil last. Rancid oil not only loses their vitamins but also develop potentially toxic compounds. These compounds can cause advanced ageing, neurological disorders, heart disease and cancer etc so people must throw away oil if it's rancid.

Also, repeated use of edible oil leads to the formation of Total Polar Compound (TPC). This compound is very harmful to humans and is unfit for their consumption. The nutritional and physicochemical properties of cooking oils are affected drastically because of reheating.

If we do not overheat the oil for a long time, don't add salt to foods before deep-frying, and if minimize food contamination by avoiding the food particles from being accumulated in the oil, then we can, to an extent, reduce the harmful effects that result while reheating oil.

Even the government has taken actions regarding the use of used oils. It introduced a set of regulations regarding the use of cooking oil in which the maximum permissible limit of TPC in cooking oil is at twenty-five per cent. The Food Safety and Standards Authority of India has been asked by the Biodiesel Association to create a nationwide ecosystem to collect used cooking oil to convert it into bio-diesel.

From July 1, 2019, all the Food Business Operators have been informed to strictly monitor the quality of the oil used for frying to see if it meets the approved regulations.

Indian masses consume approximately 23 million tonnes of oil in a year. But the cooking oil is not discarded in an environment-friendly way. If it is recycled, then about 3 million tonnes of edible oil can be recovered for producing biodiesel every year.

Hope it helps.

Oil is an essential and required thing in our everyday cooking or every Indian family kitchen. Generally, we save the leftover oil from frying Papads, Bahijas, Pooris and sauteing deep frying and making Rotis, etc and keep on using it over weeks or months till it is over. Re-using or overheating cooking oil may change its chemical compound or fats causing called polymerization. It means the structure of the fat molecule is altered forming new compounds that are inutile and in some cases unhealthy. According to the author Rudolph Ballentine of the book Diet & Nutrition, A Holistic Approach, Nutritionist expert Dr. Anju Sood and Chef Laurence Edelman, spoil or rancid oil won't make you sick or going to kill you suddenly but it ruins recipes and slowly affects our body.

Some facts we about rancid oils in relation to human health that we should understand are:
1. It is harmful to the body in the longer run - Rancid oil increase the trans-fatty acids thus increasing the bad cholesterol levels in our body, eventually blocking the arteries. It turns carcinogenic, cytotoxic and mutagenic which increases the risk of cancer. As per a study published in the journal Anticancer Research in 2002, rancid or spoil oils not only involved in tumor promotion but also in its initiation. Acidity, irritable throat and heart disease are other health hazards that can also be included in the list due to the use of spoil or rancid oil.

2. Spoil or rancid oil more Prone to Oxidation - edible oils that are rich in Polyunsaturated fatty acids (PUFAs) include the essential fatty acids and super-healthy omega-3 but are highly unstable and prone to oxidation can go rancid within a very short period of time.

3. Depleted Vitamin E - Edible oils (extra-virgin olive oil, almond oil, sunflower oil) are excellent dietary sources of vitamin E which is a powerful antioxidant that protects the body from dangerous free radicles linked with health problems and other diseases. In a study published in 1996, it found that rancid oil is capable of depleting Vitamin E levels.

Some tips to keep oil safe for reuse are as follows:
a) Try to gauge the amount of oil required for your purposes like frying, sauteing or deep frying so that you don't have much leftover oil in the pan be used next time.

b) When you know you want to preserve the used oil, Let the oil cool down, filter all the food particles from the oil, pour it in an airtight container preferably glass. Seal the container tightly and store it in a cool and dry place. It is advisable to consume the used oil first or within a month's time.

c) While re-using the oil again, check for its degradation i.e. when you start heating the oil and it smokes before it reaches the desired frying temperature or foam is formed on the surface of the oil or a dark and murky appearance, has thick texture or have a rancid odor, it may not be good to re-use.

Always try to reduce reuse and wastage of oil for better health.

It is a thinkable process as we get many adulterated oils in the market. If we get good one from genuine seller/grinder the oil after frying we can use again. But that too the oil after frying the meat or fish can be avoided for re-use. In olden days our elders used to re use the oil at least once as we got a good quality of oil that too we got the same from retailer and not in pouches/packets. Moreover our elders fry the snacks etc., by pouring the oil little by little as and when required to avoid the reminder of excess oil after the process.

Oil is an essential part of cooking. We are habitual to save the leftover oil from frying. This oil is later re-used for deep-frying or other uses. But oils become stale or rancid over time. This is because unsaturated fats present in oil breaks got broken into different compounds like aldehyde, ketone and carboxylic acid due to reaction of oxygen with carbon molecules. This gives a rancid taste to the oil. That's why oily food or even oil kept for long becomes rancid and gives very foul smell. Re-heating oil may change its chemical properties, consequently making it more harmful for the body.

If the oil has to be kept for a longer duration, it should be preserved properly in air tight bottle and in cool and dark place.

Oil should not be reheated and on reheating it undergoes a series of chemical changes and as a result of which many harmful substances are produced which may cause severe health problems in long run. Several studies also showed that continuous use of reheated oil may cause many health diseases like stomach, liver diseases, cholesterol and sometimes cancer and neurodegenerative diseases such as Alzheimer's and Parkinson's. etc.
Also reheating of oil should be avoided due to following reasons:
a. Reheating cooking oil can release harmful toxins,
b. Reheating may cause increase in the percentage of trans- fats in it makes it rancid
c. Reheating oil can deteriorate health by resulting in several harmful effects like Acidity, Heart disease, Irritable throat (due to inhalation) etc.
d. It may cause indigestion.
e. It may have bad smell
f. It may have bad flavor
g. Nutrient level also duplets on reheating.

But if you want to reuse the oil, some care should be taken. Some of tips to store the oil for further use are given below:

i) After frying let the oil cool and then strain it and ensure that no larger piece or debris is there in the oil
ii) Keep it in a air tight container
iii) Keep it in cool and dark place (you can also store it in refrigerator)
iv) T is also better to smell first before reuse.
v) Do not heat it at the smoking point
The better way is to take only small amount of oil for frying so that there will ne no left over oil and there will be no requirement of reheating of oil.
Some of the oil have a high smoke point that is they can be used for frying, deep frying and they do not break down at high temperatures. e.g. sunflower, soybean, peanut, safflower, rice bran, mustard, sesame and canola oil etc.

Olive oil is a good option if you used to reheat oil as it can be re-used more often than others. The other advantage of using this oil is that the digestibility of heated olive oil does not change even when re-used for frying several times. Some studies also shows that olive oil, having higher concentration of monounsaturated fats (such as oleic), generate harmful compounds in a smaller amount on reheating.
Further, used oil should be stored in a separate bottle and discard safely and should be handed over to used oil vendors.
So, try to take small amount while frying and avoid reheating oil.