Photo courtesy Pixabay
By Julie Garden-Robinson, PhD, LRD
“I think we need to toss the oil that is stored in the cupboard,” I said to my intern.
She agreed to do the “sniff test” on the variety of oils. She reported several of the bottles had a crayon-like aroma, a hallmark of rancidity or spoilage.
She also checked the best-if-used-by dates. Some of the oils were within their storage life, but their odor – a sign of rancidity – was… off. The bottles were in a dark place, but the room was kind of warm. Warm storage can promote rancidity, as can light and oxygen exposure.
Lately, some information widely shared on social media, such as TikTok and Facebook, has tried to sway opinions on seed oils, even if they are freshly purchased.
First, don’t believe everything you see on social media. Some of that content would make you think seed oils will reach out of the bottle and grab you by the neck.
In reality, some social media posts about seed oils causing inflammation and health issues are not fully backed up by published nutrition research. Seed oils, which include corn, soy, canola, sesame, sunflower, safflower, grapeseed and rice bran, are the types of oils we in nutrition have recommended for years.
Remember that influencers are paid based on the clicks on their content. If influencers make exceptionally provocative or scary posts, social media users are more likely to pause and read the content. Then they get deposits in their bank accounts.
When it comes to seed oils, what should a savvy consumer believe?
Let’s go back in time a bit. Oil is the name for liquid fat. Soybean oil originated thousands of years ago in Asian countries such as China and Japan. Olive oil production began about 1,000 years after soybean oil.
Oils have been used widely for many years, and then hydrogenation was invented to extend their shelf life. That process allowed the food industry to convert liquid vegetable oil to solid fat, such as the white shortening sold in cans in the grocery store.
Through research, scientists could see that changing oils from liquid to solid caused the formation of trans fat, which can raise our “bad” cholesterol and lower our “good” cholesterol.
The Dietary Guidelines and the American Heart Association recommend that we reduce our intake of saturated fat and trans fat and focus on unsaturated fat.
To understand all these terms, we have to think a bit about chemistry.
“Saturated” refers to the chemical structure of the building blocks of fat called fatty acids. If the fat is saturated, each of the carbon atoms that make up fat has a hydrogen atom attached. Saturated fat tends to be solid at room temperature.
“Unsaturated” means that the fatty acids have some double bonds in the chain of carbon atoms, so the fat is more “bendy” and flows. Unsaturated fat is liquid at room temperature.
Oils are made up of saturated and unsaturated fats. Some oils, such as olive, canola, peanut and sesame, are more “monounsaturated” (having one double bond). Other oils, such as soybean, sunflower and corn, are higher in “polyunsaturated” (having two or more double bonds) fat.
To add even more complexity, some oils are primarily made up of “omega-3” fats and others are “omega-6” fats. “Omega” refers to the position of the double bond from the end of the carbon chain. Omega-3 fats get a gold star for promoting health and are found in fatty fish, nuts and seeds, including soybeans.
Can we boil this chemistry down to something we can apply at home?
- Use a variety of oils in moderation. Some oils have a distinct flavor, while others are neutral.
- Do not be afraid of seed oils. These oils are widely recommended by leading health organizations as being good for our health.
- Consider using plant oils in place of butter. According to a 2025 publication from Harvard University, substituting plant oils (canola, soy, olive) for butter can reduce the risk of disease, and consuming plant oils is linked with a 16% decrease in mortality.
- Consume fewer ultra-processed foods, such as many commercial snack foods and deep-fried foods. Look for foods with a shorter ingredient list.
- Try to cook from scratch more often, starting with basic ingredients.
- Moderate your fat intake from all sources. Instead of frying in any kind of oil, consider roasting or grilling.
- Keep tabs on the freshness of the oils in your cupboard. Find a cool, dark place to store them. If the oil becomes rancid before you use it, consider purchasing a smaller bottle next time.
Julie Garden-Robinson, PhD, Rd, LRD, is a North Dakota State University Extension food and nutrition specialist and professor in the Department of Health, Nutrition, and Exercise Sciences.