Is Rancid Oil Dangerous for Your Health?

Most of us use cooking oil in our daily food preparation. While some smart individuals may use fresh oils for their longevity and the health benefits they offer, most people use oils beyond their expiry or best by dates, and in some cases, rancid oil.

There’s a persistent question on the minds of many people – is rancid oil harmful to your health?

What is Rancid Oil?

Rancid oil is oil that is no longer suitable for consumption, primarily because it has undergone fat oxidation or has become oxidized due to exposure to oxygen, light, or heat.

Oxidation occurs when oxygen molecules attack and break down the oil’s structure. The breakdown produces various compounds that can significantly affect the oil’s taste, smell, and quality.

It’s important to note that all oils can become rancid, regardless of their type, quality, or source.

How to Detect Rancid Oil?

The easiest way to detect rancid oil is by its odor and taste. Rancid oil has a distinct smell of varnish or old paint, and it tastes bitter and metallic.

If you’re using rancid oil in your cooking, you’ll notice that your food will have an unpleasant taste and smell.

A more professional and scientific approach to detecting rancid oil is through the peroxide value (PV) and p-anisidine value (PAV). The peroxide value measures the primary oxidation products in the oil, while the p-anisidine value measures secondary oxidation products. By measuring these values, experts can determine the oil’s degree of oxidation and the extent of its rancidity.

Is Rancid Oil Dangerous for Your Health?

Consuming rancid oil is not good for your health. The oil’s degree of oxidation affects the production of free radicals and other toxic compounds, which can lead to various health problems.

Rancid Oil and Free Radicals

Free radicals are highly reactive compounds that can damage cells, proteins, and DNA in the body. When we consume rancid oil, our bodies are exposed to free radicals that the oil produces during oxidation.

Free radicals can cause several health problems, including cancer, heart disease, and aging.

Rancid Oil and Inflammation

Rancid oil can produce inflammation in the body, which can lead to several health issues such as arthritis, asthma, and heart disease.

The toxic compounds that rancid oil produces during oxidation can trigger an inflammatory response in the body’s cells and tissues, leading to chronic inflammation.

Rancid Oil and Acrolein

Acrolein is a toxic compound that is produced when oil oxidizes. This compound can cause irritation and damage to the eyes, skin, and respiratory system.

Acrolein can also contribute to several health problems such as pulmonary edema, asthma, and bronchitis.

What are the Health Risks of Consuming Rancid Oil?

Consuming rancid oil can lead to several health problems such as:

  • Cardiovascular disease
  • Cancer
  • Arthritis
  • Asthma
  • Chronic inflammation
  • Exacerbating inflammatory bowel disease
  • Respiratory problems

Rancid oil can also have detrimental effects on nutrient absorption, affecting the body’s ability to absorb essential vitamins and minerals from food.

How Can You Avoid Consuming Rancid Oil?

Here are some tips you can follow to avoid consuming rancid oil:

  • Store your oils in cool, dark, and dry places
  • Avoid storing your oils in plastic containers as they can leach chemicals into the oil
  • Check the expiry/best by date on the oil before purchasing it
  • Use oils within their recommended shelf lives
  • Invest in smaller bottles to ensure you’re not exposing large volumes of oil to air and light
  • Avoid using oil that has an unusual odor and taste


Rancid oil is hazardous to our health, so it’s essential to exercise caution when purchasing and storing oils. Pay attention to the oil’s expiry date and follow recommended storage practices to avoid consuming rancid oil.

Frequently Asked Questions (FAQs)

  • Q: Can I reuse oil that I’ve already used once or twice?
  • A: It’s highly recommended not to reuse oils that have already been used multiple times as they may already be rancid.
  • Q: Can I cook with rancid oils?
  • A: It’s not advisable to cook with rancid oils as they can produce harmful compounds when heated, further increasing the risk of health problems.
  • Q: How long can I store oil without it becoming rancid?
  • A: The shelf life for oil depends on the type of oil and storage conditions. Check the oil’s label for information on its shelf life and storage recommendations.
  • Q: Can rancid oil still be used for skincare?
  • A: It’s not recommended to use rancid oil for skincare as it can cause irritation and breakouts.
  • Q: Can rancid oil alter the nutritional value of a food?
  • A: Yes, rancid oil can negatively affect nutrient absorption, reducing the nutritional value of the food.


  1. Hassanien, M. F. R. (2014). Rancidity in edible oils: Its impact on food quality and health and possible ways to prevent it. Innovations in Food Science and Technology, 1(1), 1-14.
  2. Bozan, B., & Temelli, F. (2008). Chemical composition and oxidative stability of flax, safflower and poppy seed and seed oils. Bioresource technology, 99(14), 6354-6359.
  3. Bendini, A., Cerretani, L., Carrasco-Pancorbo, A., Gómez-Caravaca, A. M., Segura-Carretero, A., & Fernández-Gutiérrez, A. (2007). Phenolic molecules in virgin olive oils: a survey of their sensory properties, health effects, antioxidant activity and analytical methods. An overview of the last decade. Molecules, 12(8), 1679-1719.

Leave a Reply

Your email address will not be published. Required fields are marked *