The American Heart Association wants people to know that “there’s no reason to avoid seed oils and plenty of reasons to eat them,” but some media headlines and social media influencers will ask you to believe otherwise.

To better understand seed oils and why they might be getting a bad reputation, Tufts Now consulted Diane L. McKay, an assistant professor at the Gerald J. and Dorothy R. Friedman  School of Nutrition Science and Policy and Tufts University School of Medicine, and Alice H. Lichtenstein, senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University and the Stanley N. Gershoff Professor of Nutrition Science and Policy at the Friedman School.

Tufts Now: What makes seed oils like soybean, sunflower, canola, safflower, and corn different from other oils we may cook with or consume?

Alice H. Lichtenstein: Most seed or plant oils differ from other plant oils (coconut and palm oil) by the type of fatty acids they contain. Soybean, sunflower, canola, safflower, and corn oils, as well as olive and avocado oils, are rich in unsaturated fat.  Coconut and palm oils, as well as animal fats (meat and dairy), are rich in saturated fat. There’s a tremendous amount of data that has shown if you consume plant oils high in unsaturated fat opposed to coconut and palm oils or animal fats, there are better health outcomes. 

As far as soybean oil and canola oil, soybean oil is high in polyunsaturated fatty acids, and canola oil is high in monounsaturated fatty acids. They are unique among the common cooking oils because they're also high in what's called ALA, or alpha-linolenic acid, the plant form of omega-3 fatty acids. There are some advantages to using oils, but we also get omega-3 fatty acids from most types of fish, hence, the recommendation to eat at least two servings of fish per week. 

On a daily basis people should pick the type of plant oil that they’re going to use based on personal preference and intended use. For salad dressing, you might choose olive oil, for regular sauteing, soybean oil or canola oil are great. They're affordable oils. If you're making a stir-fry dish, you might also want to use a bit of sesame oil for flavor. But choosing one oil because you think it is better than others is splitting hairs. The real focus should be on using liquid plant oils as opposed to animal fat.

Can you explain more why we should be aiming to eat more liquid plant oils as opposed to animal fat? 

Diane L. McKay: If you have a diet that's high in saturated fat and you replace the foods highest in saturated fat with foods higher in unsaturated fat, studies have shown that it will help reduce cardiovascular disease risk. 

Saturated fats in amounts that exceed your body's needs or ability to process can turn on the production of cholesterol in your liver. There’s actually more cholesterol produced in your liver per day than you would get from your diet. This cholesterol circulates around your body in lipoproteins like LDL, and can lead to increased blood cholesterol levels. In addition, saturated fat can also increase inflammation, which triggers a number of disease processes.

So, if seed oils are the healthier option, why are they getting such negative attention in the media?

DLM: The problem is not necessarily the seed oils, or the ‘hateful eight’ as they’ve been described, it’s that they are just one of many ingredients found in ultra-processed foods. If you're consuming a diet high in ultra-processed foods you are likely consuming more seed oils as well as several other ingredients like refined carbohydrates, added sugar, salt, additives and stabilizers, a combination that’s often associated with higher risk of adverse health outcomes. The real problem is that we're not getting enough omega-3 fatty acids in our diet.

Why is it important to consume omega-3 fatty acids?

DLM: Omega-3 fatty acids are essential, meaning our bodies can’t make them in sufficient quantities to meet our needs so we need to get them from food sources. They are an important component of our cell membranes, especially those found in our eyes and brain, and play a vital role in the function of the cardiovascular, respiratory, immune, and endocrine systems.

So, when it comes to choosing fats for food preparation, what advice would you give to those who shop at the grocery store?

AHL: In terms of grocery shopping, when choosing oils the best options are soybean or canola oils for most food prep needs, and other plant oils depending on the intended use and, of course, your own preference. Whole foods that contain healthy unsaturated fats include nuts and seeds, legumes and beans, as well as olives and avocados. The key is to prepare as much of your food as you can yourself. That is the best way to control what goes into your body. 

If you take this basic approach when it comes to your diet, you’re going to do very well. We’re so fortunate that we have so many choices regularly available, it’s just a matter of getting into the habit of choosing the healthier ones. 

Does that mean, if you take this general advice, you won’t have to constantly worry about the oil you choose and cook with? 

AHL: Absolutely, following the general guidance will put you on a path to eating a healthy diet. It’s important to remember, it’s about the whole diet—all the foods and beverages you choose, not necessarily individual foods. 

I’ve been asked if someone should give up butter in favor of plant oils, but my answer is always “not necessarily.” If you’re not eating a lot of meat and full-fat dairy products, you’re not getting a lot of saturated fat from those sources, so if you want a little butter, that’s fine. Whereas if you’re eating a lot of meat or full fat dairy products, then you should be a bit more concerned about your butter consumption. It has to do with balance.

If you’re ready to move toward a healthier dietary pattern, you’re best off building your basic cooking skills. It’s not worth worrying about whether to use soybean or canola oil. If somebody wants to use one of those or other plant oils—preferably not coconut or palm, that’s fine. It’s not only what you’re eating, it’s what you’re not eating. 

And lastly, covering a hot fudge sundae with a plant oil-based topping because it’s “healthy” is not going to neutralize the saturated fat and sugar. Better to share and enjoy one, occasionally.