Easily cause inflammation, deterioration and oxidation? Experts debunk 5 myths about seed oil

The term Seed oils was almost unsearched before 2022, but they are not new and have been around for decades; it refers to oils extracted from plant seeds (such as sunflower seeds, rapeseeds, soybeans, and grape seeds). They have been controversial in recent years and have been accused of being harmful to health, but scientific research and most nutrition experts disagree with these claims.

Nutritionist Jaclyn London (Jaclyn London) pointed out that seed oil is a source of unsaturated fats and contains Omega-6 fatty acids that are extremely critical to health and play an important role in cell structure, hormone production and brain function.

Current dietary guidelines recommend increasing unsaturated fat intake and reducing saturated fat, which can benefit heart health. Despite this, some lay opinions on the Internet still frequently advocate using butter, lard and butter as high sources of saturated fat to replace seed oil. With such conflicting advice so confusing, healthy living website Eating Well asked experts to debunk five common myths about seed oils.

1. Seed oil can cause inflammation

This myth stems from the fact that seed oil is rich in linoleic acid (an Omega-6 polyunsaturated fatty acid). Some studies speculate that excessive intake of Omega-6 fats may cause chronic low-grade inflammation. However, new research questions this, with multiple studies finding no link between seed oil intake and inflammation, and some even suggesting these oils may lower inflammation markers.

Another key factor is that in the standard American diet, the ratio of Omega-6 to Omega-3 fatty acids is about 20:1. This is mainly due to the fact that highly processed foods are generally rich in Omega-6 fatty acids. This does not mean that the oil itself is unhealthy. The problem is that most people do not consume enough Omega-3 fatty acids to balance this ratio. In other words, inflammation is far more affected by overall dietary patterns than seed oil alone.

London pointed out that the cooking oil chosen for cooking is far less important than the food itself and the overall eating pattern. She recommends not obsessing over specific oils, but focusing on nutrient-rich vegetables, seafood, beans, nuts, seeds, lean protein and sugar-free dairy products. At the same time, using various fats and cooking oils in moderation can form the basis of an anti-inflammatory dietary pattern.

2. Seed oil is harmful because it contains genetically modified ingredients.

Some (but not all) seed oils are derived from genetically modified plants, because crops such as corn, soybeans, and rapeseed are often genetically modified in the United States. Nutritionist Amy Brownstein points out that genetically modified crops are not harmful, but have been modified to increase their resistance to pests, thereby reducing the use of certain pesticides and insecticides.

The U.S. Food and Drug Administration (FDA) has strict safety standards for genetically modified crops and food grown in the country, and studies have confirmed that genetically modified crops are as safe as non-GM crops. If you want to avoid genetically modified products, be aware that certified organic oils may still be made from genetically modified crops.

3. Seed oils are ultra-processed foods.

Jacob Smith, Master of Science, pointed out that seed oils have indeed been industrially processed and refined, but they belong to a special category of processed foods. The widely adopted NOVA classification system classifies seed oils as processed cooking ingredients rather than ultra-processed foods. People don't consume canola oil directly as snacks or meals, but instead incorporate it into recipes or as a cooking oil, often in small amounts, and actual intakes are even lower, he said.

What’s more important is the overall diet that matches these oils. Brownstein said that seed oil is commonly found in fast food, restaurant meals and ready-to-eat foods. The other ingredients, high calories and portion size of these foods are the main reasons for the health risks associated with seed oil.

4. Seed oil can be harmful to health

Although seed oil is often blamed for various health problems, research has consistently shown that this statement is not true. Smith points out that to determine whether a substance is harmful, one should look at research data on people who actually ingested it.

Based on actual consumer data, seed oils are not associated with worse health, especially heart health. For example, a recent review study found that consuming unsaturated fats (including seed oils) is associated with lower total cholesterol and lower low-density lipoprotein (bad cholesterol). The review also found some evidence that consuming seed oils may aid weight loss and improve blood sugar management.

Regarding mortality, a follow-up study covering about 221,000 people found that daily intake of 5 grams of soybean oil or canola oil can reduce the risk of premature death by 6% and 15% respectively. The study also pointed out that replacing 10 grams of cream with vegetable oil (including seed oil) every day can reduce the risk of premature death by 17%.

Existing evidence shows that seed oil may be beneficial to health rather than harmful. The key lies in how it is used and how much it is consumed. London said that using canola oil instead of lard for frying is a step towards health, but if canola oil is used instead of lard for frying food, it may not be able to achieve the same benefits.

5. Seed oils are susceptible to deterioration and oxidation.

London pointed out that oils rich in polyunsaturated fats (such as seed oils) are more susceptible to oxidation when exposed to heat, light and air, and may produce harmful compounds. However, it is important to understand that all fats will oxidize, and the difference is only in the speed.

For this reason, nuts can last longer if frozen, and olive oil should also be stored in a cool, dark place. This principle applies to all oils and fats: place them in dark-colored bottles away from light and heat environments that accelerate oxidation and deterioration; otherwise, it is equivalent to claiming that "blueberries will eventually become moldy and therefore should not be eaten." The key is to store them properly and eat them within the expiration date.