Seed oils include sunflower, rapeseed, corn and grapeseed oils. High heat, chemical solvents and extreme pressure are used to extract the oil from plant seeds. They are then further refined to stabilise it.
These refining processes can affect the chemical compounds of the oil, reducing the amount of healthy antioxidants, polyphenols and phospholipids. However, this process gives the oil a longer shelf life and stabilises the oil so that it doesn’t burn at high temperatures
Many social media influencers claim that seed oils contain toxins. But most of these compounds, such as pollutants and heavy metals, are removed during refining. The amount that is left is too small to cause humans any harm.
The main issue with these oils is that some fast-food outlets reuse them to cut costs. Once reused and reheated, trans fats, which increase “bad cholesterol” and decrease “good cholesterol”, can form in the oil. However, most health and safety regulations ban the reuse of oils in food establishments.
Most seed oils are rich sources of omega-6 fatty acids. According to decades of rigorous research, these unsaturated fatty acids have many health benefits. They are linked to reduced risk of heart disease and improvements in cholesterol levels.
These benefits were highlighted in epidemiological studies when people replaced animal fat and saturated fatty acids with omega-6 fatty acids and vegetable oils. Replacing saturated fatty acids with polyunsaturated and mono-unsaturated fatty acids from plant sources significantly reduced the risk of heart disease in different populations.
However, they do have some drawbacks. Omega-6 can increase the risk of inflammation throughout the body. Inflammation is linked to many chronic diseases, including heart disease and diabetes.
Studies show that omega-6 intake should be limited and tempered by consuming omega-3 fatty acids, which are anti-inflammatory.
It’s all about the ratios
A healthy diet should ideally have an omega-6 to omega-3 ratio of four to one (4:1). A diet with omega-3 can help control the harms of overconsumption of omega-6 from seed oils. However, different ratios of omega-6 to omega-3 fatty acids can help reduce the risk of certain chronic diseases. For example, a ratio of 5:1 may be beneficial for people with asthma. And ratios of 2:1 to 3:1 have been shown to reduce inflammation in people with rheumatoid arthritis.
In recent years, the ratio between the amount of omega-3 and omega-6 consumed has been trending in an unhealthy direction: people are consuming much more omega-6 than omega-3, with a ratio of 15:1 in some cases.
So if you’re looking for a healthier ratio, eat more foods rich in omega-3, such as seafood, avocado and nuts. Some oils, such as olive oil, are also rich in omega-3. However, olive oil may not be the best oil to cook with as some people believe it is unstable at high heat.
As long as people consume enough omega-3, the consumption of omega-6 would not cause inflammation. In fact, their combined intake would reduce the risk of several chronic diseases, such as heart disease and diabetes.
While seed oils are not toxic, fat intake should be moderated in any diet to maintain good health. Fat intake is essential as it helps with the absorption of fat-soluble vitamins (vitamins A, D, E and K), the deficiency of which can have dire consequences for your health.
A diet with some seed oil will not cause ill health. Seed oils also do not cause obesity, as some people are claiming. Obesity is linked to multiple factors beyond the type of oil being consumed. There is a stronger association between obesity and the amount rather than the type of oil consumed.
The main issue with seed oils is that they are mostly found in highly processed food and fast food. Reducing the intake of ultra-processed food, whether made with seed oils or not, would have more health benefits than simply cutting down on seed oil. A lot of these foods are high in refined sugar, trans fats and salt, which do more damage to health than seed oils.
Evidence shows that seed oils are a healthier alternative to animal fats. Decades of evidence show a clear link between the replacement of animal fat with plant-based oils with a reduced risk of heart disease.
For people cooking at home, a bit of oil, whether seed or fruit oil, will not damage your health. Used in moderation and as part of a varied, whole-foods-based diet, seed oils can be a valuable addition to a healthy lifestyle. As with all foods, moderation is key.
Raysa El Zein, Lecturer, Life Sciences, University of Westminster
This article is republished from The Conversation under a Creative Commons license. Read the original article.