It’s hard to keep up with which foods and beverages you’re supposed to avoid. One of the latest foods to come under fire are seed oils. These highly processed oils made from canola, sunflower, corn, soy and other plants are popular for cooking. However, some nutritional experts argue that the fatty acids in seed oils could cause inflammation and other health problems.
Do we have to give up vegetable oil forever? Here’s what science says.
The origin of seed oils
Prior to the 20th century, no one was cooking with seed oils. Enter Crisco: this cooking fat, which resembles lard, is derived from cottonseed oil. Proctor & Gamble, the manufacturer, started advertising Crisco as being healthier than using animal fats. Their marketing gambit paid off: they sold tens of millions of pounds of Crisco in just five years.
After Crisco’s smashing success—it’s still on the shelves today, by the way—other manufacturers started experimenting with seed oils. Today, it’s easy to find canola, soy, sunflower and corn oil in any grocery store.
Seed oils are extracted by either milling or using a chemical solvent. They’re usually purified, refined and even chemically altered. Today, they’re sold with labels like “heart healthy,” due to their polyunsaturated fat content, but some dieticians disagree.
What do the experts say?
Mainstream nutritionists and scientists don’t consider seed oils any unhealthier than other cooking oils. As long as you consume seed oils in moderation, they are safe to consume. (Just keep in mind that oils have about 120 calories per tablespoon, which adds up fast.)
On the other hand, some dieticians believe that the omega-6 fatty acids in seed oils will cause inflammation. For instance, Dr. Cate Shanahan calls canola, corn, cottonseed, soy, sunflower, safflower, grapeseed and rice bran oils “the hateful eight.” She argues that these eight oils are “very high in polyunsaturated fatty acids (PUFAs), which promote inflammation and the accumulation of toxins in body fat.” This is primarily due to the way seed oils are extracted: she believes the chemical solvents used affect the end product. She claims that consuming large amounts of seed oils increases inflammation, causing Alzheimer's, cancer, autoimmune diseases and obesity, among other conditions. She also claims that inflammation makes people more vulnerable to COVID-19.
It's true that most people take in more omega-6 fatty acids (which are richer than omega-3s found in fatty fish, olive oil, avocados and more). It’s also true that omega-6 fatty acids can contribute to inflammation, and seed oils have a higher trans fats content. Unfortunately, studies report inconsistent findings.
This study failed to find any support for the idea that vegetable oils increases inflammation. But this study finds linoleic acid, found in seed oils, is associated with a higher risk of coronary disease. And this review of multiple studies links high levels of linoleic acid to “reduced risk of cardiovascular events.”
Should you avoid seed oils?
To say the evidence is inconclusive might be a bit of an understatement. It might be a while before we find out once and for all whether seed oils are bad for us.
When adjusting your diet, the most important thing is to eat as many whole, unprocessed foods as possible. Seed oils are especially present in processed junk foods, like candy, cookies, salad dressing and even hummus. Keep your oil consumption down by cooking your own foods and avoiding processed, packaged foods at the grocery store.
If you’re dedicated to reducing inflammation as much as possible, there are plenty of other oils to try: coconut, olive and avocado oils boast more nutritional benefits than seed oils.
Olive oil is every dietician’s darling. Rich in omega-3 fatty acids (the good kind, which fight inflammation), it’s great in salad dressings and adds great flavor to meat, vegetables and other dishes.
Coconut oil is also great for boosting energy, fighting inflammation and maintaining good blood sugar levels. It can be used in both sweet and savory dishes, but it may impart a subtle coconut flavor to your food.
Avocado oil, like olive oil, is full of antioxidants and oleic acid, a healthy fat. It’s also full of vitamin E, which is important for eye and skin health. Avocado oil is quite neutral, so it won’t overpower your food like olive oil can.
Ultimately, whether you eschew seed oils or decide the benefits outweigh the drawbacks, the key is to keep your oil consumption as minimal as possible.