What is the unhealthiest oil?

The Unhealthiest Oils You Should Avoid

Not all cooking oils are created equal—some can actually do more harm than good. Highly refined oils, in particular, have come under fire for their potential to trigger inflammation and contribute to long-term health issues. Among the worst offenders are soybean, corn, and canola oils, which are commonly found in processed foods and restaurant kitchens.

Soybean oil dominates the U.S. market, but research links it to increased inflammation and elevated levels of ApoB, a protein associated with harmful cholesterol particles. Its high omega-6 fatty acid content, when consumed in excess, can throw off the body’s omega-6 to omega-3 balance—a key factor in chronic inflammation.

Corn oil is another culprit. While technically “vegetable” oil, it’s far from healthy. It’s loaded with omega-6 fats and often undergoes high-heat processing, which can cause oxidation. These oxidized compounds may damage cells and contribute to heart disease over time.

Canola oil is frequently marketed as a “heart-healthy” choice, but the reality is more complicated. Most commercial canola oil is highly refined and derived from genetically modified crops. While unrefined, cold-pressed canola oil may have some benefits, the refined version used in most packaged foods can degrade into harmful substances when heated.

Other oils to watch out for include cottonseed and sunflower oil (especially when refined), both of which are often high in saturated fats or inflammatory compounds due to processing methods.

The key isn’t to eliminate fats—our bodies need them—but to choose wisely. Opt for less processed, stable fats like extra virgin olive oil, avocado oil, or coconut oil in moderation. When reading labels, avoid anything that lists “partially hydrogenated” oils or vague terms like “vegetable oil,” which usually hide the less healthy options. Your long-term health might just depend on it.