Can vegetable oil go bad?

In this brief article, we are going to answer the question “can vegetable oil go bad?” by providing answers related to the shelf life of vegetable oil, how long it lasts, how to identify stable vegetable oil, and how to store it correctly.

Can vegetable oil go bad?

Yes, vegetable oil can go bad. Oils are nothing more than fat. Chemically, fat in food  is mostly formed of fatty acids glued together to form triglycerides. 

You have probably heard about triglycerides because they are also present in your blood, and knowing their level is part of that long list of exams during your annual health check-up.

Actually, every fat (the one in red meat, in butter, in porc fat)  is primarily made of triglycerides. But triglycerides in vegetable oils are majorly constituted of a special type of fatty acids, the ones that are highly prone to reactions with air (oxidation).

When vegetable oils undergo oxidation, a chain of complex chemical reactions takes place whose main final results are the appearance of off-flavors (rancidity), nutrient losses, and even toxic compounds [1]. 

How long does vegetable oil last?

An unopened bottle of vegetable oil lasts for six months to one year, according to manufacturers. But this limit date may vary among countries. 

When you open a vegetable oil bottle, the shelf life will depend on the handling practices, but as a rule of thumb, it is reduced. The reason is that when you open a bottle of vegetable oil, it gets exposed to air, promoting oxidation.  

Even though the quality does not deteriorate immediately, it happens over time because so far, fat oxidation cannot be avoided, just delayed. 

But if you stock the oil bottle fastened, safe from excessive heat and light incidence, it can last the whole shelf life period indicated on the label without any significant sign of rancidity.

How to tell if your vegetable oil has gone bad?

Smelling is the best way to know if a vegetable oil has gone bad. Oxidation is easily recognized as rancidity. For this reason, usually, it is not necessary to taste it, just sniff it. 

You can also observe the oil color and consistency. Most oils come in clear bottles, so when having look at it, the oil should be translucid. 

Turbidity and viscous consistency indicate extensive oxidation and oil like that should be immediately discarded.  

All vegetable oils come with a best-before date. This date helps you judge the quality of the oil and it is usually not a determining factor when it comes to the safety of the vegetable oil.

Can you get sick from eating rancid vegetable oil?

No, you do not necessarily get sick from eating rancid vegetable oil. Pathogenic microorganisms (those causing foodborne diseases) cannot grow in oils. It will mostly just taste unpalatable which will make you want to throw it away.

If you feel like you have consumed rancid vegetable oil, it is not a cause for concern and you will not see any immediate side effects.

But in long term, it is not safe continuously ingest oxidized vegetable oil. This is because oxidized fat and oxidized fat-derived compounds are toxic to the human body and may cause or worsen certain types of pathologies.

A number of studies have described the adverse implications of oxidized fat in the human body [1, 2, 3].

What are the health hazards of consuming rancid vegetable oil?

The long-term health hazards of consuming rancid vegetable oil are cellular damage. Previous research showed that rancid vegetable oil contains free radicals, which are highly reactive molecules capable of harming cell membranes, proteins, and DNA [1].

Free radicals are involved in numerous pathological states including several age-related neurodegenerative diseases, such as Alzheimer’s [3].

In addition to free radicals, oxidized oils can also contain toxic compounds derived from the extensive transformation of fatty acids due to oxidation reactions.

According to studies, some of these compounds can be pro-carcinogenic and alter cell functions [2,3]. 

So the best way to avoid these health hazards is not to consume oils that you perceived as oxidized. You should also store vegetable oils correctly to minimize oxidation, and consequently, the formation of undesirable toxic compounds.

What does affect the shelf life of vegetal oils?

Heat, light, and oxygen are the main factors that affect the shelf life of vegetable oils because they are critical parameters that catalyze oxidation reactions.

This means that vegetable oils exposed to direct sunlight incidence, heat, and air will oxidize much faster than oils kept sealed and safe in a pantry [4]. 

For example, frying accelerates oil oxidation [4]. With repeated frying cycles, oxidation-derived compounds accumulate in frying oils up to a level that becomes unpalatable and dangerous to health, according to research [4].

How to properly store vegetable oils?

Vegetable oils should be stored in a cool, dry, and dark place, away from the stove because of the heat.

If stored correctly, vegetable oils can last the whole best-before date and a bit more, as long as it still owns proper taste, color, and smell characteristics. Just be mindful and if you have doubts it is best to throw them away. 

What to do with vegetable oils that have gone bad?

Follow these tips if you do not know how to proceed with bad vegetable oils:

  • Never throw the oil in the sink! Place the oil in a container with a lid — a PET bottle, for example. Look for the nearest collection point.
  • If your city does not have a collection point, place the bottle with oil next to the garbage to be collected. 

These actions reduce the risks of soil and water resource contamination.

  • You can deliver it to experts in making homemade soap. As Francischi [5] explains, it is possible to make soap from cooking oils, but it takes caustic soda, which is very corrosive.

Thus, it is more advisable to give vegetable oil to professionals or take lessons with experts on how to do it before making your soap.


In this brief guide, we discussed the query “can vegetable oil go bad?” by providing answers related to the shelf life of vegetable oil, how long it lasts, how to identify stable vegetable oil, and how to store it correctly.

If you have any comments or questions please let us know.


1. Vieira SA, Zhang G, Decker EA. Biological Implications of Lipid Oxidation Products. Journal of the American Oil Chemists’ Society. 2017;94(3):339-51.

2. Di Domenico F, Tramutola A, Butterfield DA. Role of 4-hydroxy-2-nonenal (HNE) in the pathogenesis of alzheimer disease and other selected age-related neurodegenerative disorders. Free Radical Biology and Medicine. 2017;111:253-61

3. Zarkovic K, Jakovcevic A, Zarkovic N. Contribution of the HNE-immunohistochemistry to modern pathological concepts of major human diseases. Free Radical Biology and Medicine. 2017;111:110-26.

4. Seppanen CM, Saari Csallany A. Formation of 4-hydroxynonenal, a toxic aldehyde, in soybean oil at frying temperature. Journal of the American Oil Chemists’ Society. 2002;79(10):1033-8.

5. Transforming waste into soap. Available on: