Scroll through social media or watch any newscast and you may be confused by conflicting health claims about cooking oils. Should you steer clear of seed oils? Is avocado oil the best? Is beef tallow a healthful alternative for cooking French fries? And what happens when you cook with various oils or fats? Is there a link to cancer?
A wealth of scientific research may help guide your choices when it comes to which oil to use. But, as Elaine Siu, MS, RD, CNSC, CSO, Clinical Nutrition Services Supervisor at City of Hope® Cancer Center Duarte, notes, it may be disappointing to hear, but there is no one food—or cooking oil—that is the ticket to good health.
“I can say there is a lot of good evidence that things like olive oil, oils from seafood, from fish, avocado oil—those are good for you—whereas things like animal fat are generally quite high in saturated fats. Many studies have shown there are risks for eating a high saturated fat diet,” Siu says. “But, if you look back over time, moderation and balance are always the keys. We go through phases—a while back everything needed to be low fat. Now we're saying, ‘Oh, no sugar; avoid sugar.’ At the end of the day, the most important thing is that you eat a generally well-balanced diet containing a lot of fruits and vegetables, healthy fats, lean protein. That's what really is most important.”
This article examines different types of healthy—and not so healthy—fats and cooking oils, explaining:
- What are seed oils?
- Are seed oils bad for you?
- What is tallow?
- Tallow and your health
- Does cooking oil cause cancer?
- Which oils should you eat?
If you’ve been diagnosed with cancer and are interested in getting a second opinion of your diagnosis or treatment options, call us or chat online with a member of our team.
What are seed oils?
Seed oils are derived from the seeds of certain plants. Common varieties used in home-cooked as well as manufactured foods include:
- Canola or rapeseed oil from the seeds of the yellow-flowered canola or rapeseed plant
- Corn oil derived from corn kernels
- Cottonseed oil extracted from the seeds of cotton plants
- Soybean oil
- Safflower oil
- Grapeseed oil made from grape seeds
- Rice bran oil from the bran layer of rice grains
- Sesame seed, sunflower seed and flaxseed oils derived from those particular seeds, which may also be eaten as whole seeds
According to Siu, seed oils contain unsaturated fat, “which generally is better for you than saturated fat.” According to the American Heart Association, eating more unsaturated fats instead of saturated fats can help reduce the risk of heart disease.
Other oils derived from plants include avocado oil, olive oil, coconut oil and peanut oil, which have varying levels of unsaturated and saturated fat and nutrients. For instance, coconut oil has about 85 percent saturated fat and should be used in moderation. Olive oil, particularly extra virgin olive oil, is rich in monounsaturated fats, along with healthful vitamins and antioxidants.
“Avocado oil is a a healthy choice,” Siu says, “but if you have an excess amount, it still is going to cause weight gain, which can lead to obesity and then increase the risk for a chronic disease. So, bad or good oils, it all comes down to the total amount you're eating.”
Are seed oils bad for you?
Seed oils have been maligned recently because they often contain omega-6 fatty acids, which, unlike the more commonly discussed and desirable omega-3 fatty acids found in fish and seafood, are not considered healthy.
But Siu says our bodies need both omega-6 and omega-3 fats. “We cannot function without these essential fatty acids— omega-3 and -6. We need to get them from our diets. Seed oils tend to be higher in omega-6, and there is concern that very high intake or excessive intake of omega-6 will cause more inflammation,” she explains. “Again, it’s really important to focus on moderation. We don't want to be taking excessive amounts of omega-6, just like you don’t want an unlimited amount of saturated fat. If you take a moderate amount of [seed oils], then that's totally fine. It's part of a healthy diet.”
Another concern with seed oils is that they may be processed using the chemical hexane, which quickly and efficiently extracts oil from the plant seeds. Hexane is toxic, particularly when inhaled, and prolonged exposure can cause neurological damage.
But Siu cites studies that have shown “the amount of hexane left in processed oils is a very, very minute amount.”
Really, the health issues with seed oils are linked to their use in unhealthy, processed foods.
“Fast food, fried chicken, French fries—this is where we get most of these oils,” Siu says. “When you're eating an unhealthy, unbalanced diet, not eating fruits and vegetables, fiber, you can get chronic conditions. So, I think that's the problem—the American diet generally is just not balanced. You can't really demonize that one component.”
What is tallow?
Tallow is made by heating animal fat, specifically beef fat, over low heat to separate it from other tissues and impurities in the meat in a process called rendering. At room temperature, rendered fat is solid.
Other animal fats used for cooking include:
- Lard, which is rendered from pig fat
- Schmalz, rendered from chicken or poultry fat
- Bacon fat rendered from bacon and pancetta
- Butter churned into a solid from milk fat
- Ghee, which is clarified butter or butter simmered over low heat to remove the milk solids
Since tallow and these other fats are made from rendered or clarified animal fat, they may not be appropriate for a vegetarian or vegan diet.
Tallow and your health
While beef tallow contains trace amounts of healthful omega-3 fatty acids and vitamins, it also is high in saturated fat, which has led the American Heart Association and the Physicians Committee for Responsible Medicine to advise against using it for cooking.
“Scientific studies show that beef tallow poses concerns for heart health. Beef fat is approximately 50 percent saturated fat, which raises cholesterol levels,” said Anna Herby, DHSc, RD, CDCES, a nutrition education specialist with the Physicians Committee for Responsible Medicine, in a news alert. “While the beef industry has suggested that the stearic acid in beef should limit its cholesterol-raising effect, testing shows that beef tallow has cholesterol-raising effects similar to that of other meats.”
A Japanese study showed specifically that consuming beef tallow is linked to the increased risk for developing intestinal and prostate cancer in rats.
Many studies over the years have established a link between a diet high in saturated fat and cardiovascular disease and other chronic conditions. Based on this research, the current U.S. Department of Agriculture’s Dietary Guidelines recommend limiting saturated fat consumption to less than 10 percent of daily calorie intake.
The USDA’s Dietary Guidelines Advisory Committee’s Scientific Report, released in December 2024, states: “Evidence indicates that when reducing butter, processed and unprocessed red meat, and dairy, substitution or replacement with a wide range of plant-based food sources, including plant-based protein foods (e.g., beans, peas, and lentils), whole grains, vegetables, or monounsaturated fatty acid (MUFA)- and PUFA-rich vegetable oils and spreads, is associated with cardiovascular disease risk reduction.”
More recently, a study published in JAMA Internal Medicine showed that replacing butter, which is high in saturated fat, with plant-based oils, including olive, soybean and canola oil, may help prevent death from heart disease as well as cancer. The researchers write: “These results support current dietary recommendations to replace animal fats like butter with nonhydrogenated vegetable oils that are high in unsaturated fats, especially olive, soy and canola oil.”
Does cooking oil cause cancer?
Siu says research has yet to establish a direct link between consuming any particular type of cooking oil and cancer in humans. However, she says, “I would not be surprised if research does continue to show that saturated fats contribute to more inflammation, more weight and then cancer.”
While eating oils high in saturated fat may not be directly tied to cancer, studies have shown that heating these oils to a high temperature to the point they are burning or smoking creates carcinogenic fumes containing polycyclic aromatic hydrocarbons (PAH) and aldehydes.
For this reason, it’s important to know when to use specific oils and guard against heating them to the point of smoking. Certain oils like flaxseed oil and extra virgin olive oil have lower smoke points making them appropriate for low temperature cooking, salad dressings or tossing with pasta. Avocado and canola oils have high smoke points making them versatile oils good for stir frying, sautéing and deep frying. Butter and coconut oil have medium smoke points.
Research published in Critical Reviews of Food Science and Nutrition has shown that reheating vegetable oils repeatedly may produce harmful fumes associated with higher risks of colorectal, breast and prostate cancers in those exposed to the fumes over extended periods.
And Siu notes that reheating oils also diminishes any nutritional value they may have, adding that even before cooking with the oil “the more refined, the more processed [the oil], the fewer nutrients, too.”
Which oils should you eat?
When selecting a cooking oil, there are many considerations: how you will use it; healthy properties; cost and, of course, taste.
“For myself, I generally use canola or avocado oil for stir fries and sesame oil for drizzling when I’m making Asian cuisines and olive oil for everything else,” Siu says. “I like olive oil for most foods. But they are more expensive, so, for some people, this is not always an economic choice because of the cost. Avocado oil is even more expensive, but it is very versatile—you can use it in many different ways since it has a high smoke point and a mild flavor making it suitable for almost any cuisine.”
She notes that using an oil spray can be a smart choice for many people. “It helps you use less oil overall, which can reduce fat intake, and since you're only using a small amount, it's easier to justify spending a bit more on a higher-quality option.”
“Whenever you can, find the one that has the least processing. Look for ‘cold press’ on the label,” she advises. “Again, these will also cost more. So, it's kind of a balance. Whenever you have to choose, any kind of plant oil is better than saturated fat. In general, you would want to steer clear [of animal fats]—if you want to have butter make it a kind of special treat. That's your goal.”
If you’ve been diagnosed with cancer and are interested in getting a second opinion of your diagnosis or treatment options, call us or chat online with a member of our team.
