Seed oils have been at the center of a heated debate about their impact on health. Critics argue that these oils contribute significantly to inflammation, leading to various health issues like type 2 diabetes, obesity, cardiovascular disease, and cancer. However, recent studies and expert opinions challenge this notion, suggesting that the role of seed oils in inflammation is more complex than previously thought.
Research has shown that more than 15 randomized control trials have found refined seed oils to have no effect on inflammation, with some even indicating potential anti-inflammatory properties. Linoleic acid, a key component in oils such as sunflower and grapeseed, typically lowers inflammation. This contradicts the common belief that seed oils are inherently harmful due to their omega-6 fatty acid content.
“There’s overwhelming evidence that seed oils are not inflammatory.” – Sarah Berry
Omega-6 fatty acids are often blamed for the inflammatory reputation of seed oils. These are a type of polyunsaturated fat found in many seed oils. However, experts like Sarah Berry emphasize that inflammation is a natural and necessary process for the body to heal from harm.
“The reason seed oils are often believed to be inflammatory is that many have a high amount of omega-6 fatty acids, a type of polyunsaturated fatty acid,” – Sarah Berry
“However – and this is really important – we know that inflammation is a crucial part of the body’s natural processes.” – Sarah Berry
“It’s part of our normal physiological reaction to harm, for example. When you cut yourself, the only reason you heal is because you have an inflammatory reaction.” – Sarah Berry
The method of processing seed oils has also raised concerns. Hexane is commonly used to extract oil from seeds. However, after extraction, hexane is removed through distillation and evaporation, leaving only trace amounts. The European Union regulates this process, allowing a maximum residual limit of just 1 mg of hexane per kilo of oil. For individuals seeking alternatives, cold pressing offers a method of oil extraction without the use of hexane.
Despite the increase in seed oil consumption over the past five decades, coinciding with rising rates of cardiovascular disease, cancer, obesity, and type 2 diabetes, experts caution against drawing direct causative conclusions. Sarah Berry suggests that the mechanistic theory linking seed oils to inflammation does not hold up when examined closely.
“The idea that we’re going to suffer from inflammation seems to be this mechanistic theory that doesn’t play out in reality.” – Sarah Berry
“That’s because our bodies are so clever; what happens in a petri dish or even a mouse isn’t what happens in humans.” – Sarah Berry
While omega-6 fatty acids can exhibit inflammatory properties, they can be beneficial when consumed in balance with omega-3 fatty acids, which produce anti-inflammatory chemicals in the body. Omega-3s are found in fish and nuts and serve as an important dietary component for reducing inflammation.
Cooking methods also play a crucial role in the health impacts of seed oils. High-temperature cooking can degrade these oils, creating unhealthy compounds. Repeated frying or prolonged exposure to air can further deteriorate their quality. Sunflower oil, for example, is unsuitable for high-heat cooking due to its high polyunsaturated fat content.
In the UK, popular seed oils include rapeseed, sunflower, soybean, corn, grapeseed, rice bran, and safflower. These oils represent nearly all the fats consumed from seeds in British diets.
“In the UK, the largest contributor of fat in most people’s diets is palm oil, which is often used for deep frying.” – Sarah Berry
“Nearly all the rest of the oils that we consume come from seeds.” – Sarah Berry