What science says about using seed oils in our diets

An anti-seed oil movement has proliferated on social media platforms and has continued to grow as well-known public figures and influencers have attributed common health problems like heart disease, diabetes and cancer to consuming seed oils. Seed oils are cooking and salad oils pressed from seeds like canola, corn, cottonseed, sunflower, safflower, grapeseed and soy. However, a substantial body of peer-reviewed scientific evidence doesn’t support these negative claims.

What does science say about seed oils, and should we be steering away from them or not?

Recently, health food grocer Erewhon and national restaurant chains including Sweetgreen and True Food Kitchen have announced transitioning away from the use of seeds oils. These companies are clearly trying to appeal to the demands of their health-conscious customers, but is the departure from seed oils science-backed or merely misinformation?

The primary claims against seed oils are related to their omega-6 fatty acid content and the refining process used in extracting them.

Seed oils are rich in omega-6 fatty acids, especially linoleic acid. Seed oil critics reason that there are pathways in which linoleic acid is converted in the body to other polyunsaturated fatty acids associated with inflammation. However, an overwhelming majority of published scientific literature points to the safety and potential health benefits of linoleic acid in reducing inflammation and risk of coronary artery disease, stroke and type 2 diabetes. Contrary to claims that omega-6 fats promote inflammation, research indicates that they do not have harmful pro-inflammatory effects when consumed as part of a balanced diet.

Another purported risk of seed oils is due to the use of heat and solvents, such as hexane, in processing and extraction, creating chemical contaminants and unhealthy trans fats. However, seed oils contain little residual hexane. The brief heating process creates insignificant levels of trans fats. Mechanical pressing, like cold or expeller pressing, is an alternative to hexane extraction, but usually produces oils with lower smoke points, shorter shelf lives and higher prices. Consumers can limit their trans fat intake by steering away from hydrogenated oils, typically labeled in the ingredient list on food packaging, and avoid prolonged periods of high heat cooking and deep frying.

Ultimately, monounsaturated fats (MUFAs) and polyunsaturated fats (PUFAs) are essential for good health. They help maintain healthy cholesterol levels, reduce inflammation and reduce the risk of heart disease and stroke. Saturated fats and trans fats found in butter, shortening, coconut oil and palm oil should be limited due to their ability to raise cholesterol. Trans fats, in particular, are associated with inflammation and negative changes in the brain. Keep in mind that most sources of dietary fats contain a combination of MUFAs, PUFAs and saturated fats.

For everyday cooking and meal preparation, it’s advisable to choose oils that are stable at high temperatures and offer health benefits. Here are some options:

• Extra Virgin Olive Oil (EVOO) – Rich in monounsaturated fats and antioxidants, EVOO is well-established for its heart health benefits and is suitable for most cooking methods.
• High-Oleic Sunflower and Safflower Oils – These oils have a higher monounsaturated fat content and are more stable for high-heat cooking compared to their regular counterparts.
• Avocado Oil – With a high smoke point and a favorable fat profile, avocado oil is excellent for high-heat cooking and also provides beneficial nutrients.
• Canola Oil – A cost-effective option, canola oil contains omega-3 fatty acids and phytosterols that can help lower cholesterol levels.

It’s important to make food choices for health based on sound scientific information, not unwarranted fear or misinformation. The spread of inaccurate or alarmist information about seed oils can create unnecessary stress and anxiety about food. The current science doesn’t suggest that totally avoiding seed oils would result in a measurable improvement in health and wellness.

LeeAnn Weintraub, MPH, RD is a registered dietitian, providing nutrition counseling and consulting to individuals, families and organizations. She can be reached by email at RD@halfacup.com.