3 best and 3 worst oils for cooking and the common mistakes that turn them toxic

Cooking oil looks simple, but it behaves like a chemical. Heat it too much, reuse it incorrectly, or pick the wrong oil for the wrong style of cooking, and it can quietly turn toxic, releasing compounds that inflame your gut, stress your liver and harm your heart. Most Indian kitchens rely on just one oil for everything, but experts say each oil has its own personality: some thrive in heat, some collapse. Here’s a look at the three best oils for Indian cooking, the three worst, and the everyday mistakes that make even “healthy” oils harmful.

Mustard oil has been used for centuries because it can handle high heat, adds flavour, and contains natural antioxidants. Its high smoke point (around 250°C) makes it ideal for tadkas, sabzis and shallow frying. And unlike refined oils, cold-pressed mustard oil retains omega-3 fats that support heart and brain health.
Why it’s one of the best:
•Extremely stable at high temperatures
•Rich in anti-inflammatory compounds
•Improves digestion and metabolism
•Great for Indian masala cooking

Peanut oil is naturally stable, nutty and excellent for frying. It doesn’t break down easily, which means fewer harmful byproducts during high-heat cooking. It also contains vitamin E, which supports cell repair and immunity.

Why it’s great:
•High smoke point
•Ideal for deep frying and stir-frying
•Doesn’t turn bitter or smoky easily

Extra virgin olive oil (EVOO) is a heart-health superstar thanks to its antioxidants and monounsaturated fats. But the truth is: it’s not meant for heavy frying. Use it for low-heat cooking, light sautés, eggs, pasta, and salad dressings.
Why it belongs on the best list:
•Rich in polyphenols that protect the heart
•Supports gut health
•Great for finishing dishes
Tip: Use EVOO for low to medium heat, and use mustard or groundnut for high-heat cooking. No single oil fits all tasks.

Sunflower, soybean, rice bran, and “vegetable oil blends” sound healthy, but the refining process strips nutrition and pumps them full of chemicals, bleaching agents and stabilisers. When heated, they release aldehydes - harmful compounds linked with inflammation and oxidative stress.

Why they’re among the worst:

•Break down quickly when heated
•Can disrupt gut health
•Linked with higher inflammation over time

Still used in halwai shops, vanaspati and margarine contain trans fats, the single most damaging fat for the heart. Even small amounts increase bad cholesterol and inflammation.

Why avoid it completely:

•Very high in trans fats
•Increases heart disease risk
•Creates free radicals during heating

Heavily marketed as “healthy,” most canola oil available in India is refined, deodorised and stabilised using high heat and chemicals. It has a decent fatty acid profile but breaks down fast at high temperatures, exactly how most Indian cooking works.

Why it makes the worst list:

•Unstable during frying

•Loses nutrition quickly

•Releases harmful oxidation compounds

• Heating oil beyond its smoke point
  Each oil has a limit. Once it starts smoking, it’s literally burning, releasing toxic fumes and breaking down into free radicals.
  
• What to do instead:
  Use mustard/groundnut for high heat, olive oil for low heat, and switch off the gas the moment the oil starts smoking. Even a few extra seconds of overheated oil can damage nutrients and alter the taste of your entire dish, so stay alert.
  
• Reusing the same oil again and again
  That big kadhai of “fried once, save for later” oil is a huge mistake. Reheated oil becomes thick, sticky and loaded with aldehydes that stress the liver and inflame the gut.
  
• Rule:
  Never reuse oil more than once. If it smells “old,” throw it. Your organs pay a bigger price than the few teaspoons you think you’re saving.
  
• Storing oil in sunlight or near the stove
  Light + heat = oxidation. When oils oxidise, they turn rancid (even before you can smell it).
  Fix:
  Store oils in airtight, dark containers away from direct sunlight. A cool shelf is better than the countertop, and it keeps the flavour cleaner for longer.
  
• Mixing multiple oils in the same kadhai
  People often keep topping up the same oil with whichever bottle is nearby. Different oils have different smoke points; mixing confuses the chemistry and speeds up breakdown.
  This leads to unstable fats, faster oxidation and a strange aftertaste you may not notice immediately.
  
• Ignoring the type of cooking
  Using olive oil to deep fry pakoras or refined sunflower oil for tadka is both wrong for heat stability.
  Quick guide:
  • High heat: mustard, groundnut
  • Medium heat: sesame, coconut
  • Low heat: extra virgin olive oil
  Choosing the right oil isn’t fancy, it’s foundational. The wrong match can ruin nutrients, flavour and gut health, while the right one elevates every bite.