A decision on the best oil for deep frying should be based on how it responds to heat. A recent study indicates extra-virgin olive oil may beat sunflower or vegetable oil for cooking.
High temperatures in frying cause oils to decompose and produce polar compounds, which have adverse health effects. Instead of the problem being related to an oil's smoke point as previously thought, oxidative stability and other factors more accurately predict its performance, concludes a June 2018 study published in Acta Scientific Nutritional Health.
How Oils Compare When Heated
The authors of the Acta Scientific Nutritional Health study challenged the belief that a cooking oil's smoke point correlates with safety. Because the field of research offers little evidence to support the theory, they wondered if other characteristics of the oil might play a more prominent role in performance when heated. After exposing common cooking oils to high temperatures for prolonged periods, they made several discoveries.
Their experiment revealed that a high smoke point wasn't related to oil safety. In fact, the higher the oil's smoke point, the more polar compounds it produced. Results showed that during heat exposure, extra-virgin olive oil created the least amount, followed by coconut oil and other virgin oils like avocado oil and high-oleic seed oils. Although canola oil has a reputation for being healthy, it produced the most polar compounds when heated.
Choice of Oil Matters
The University of Rochester Medical Center says that many restaurants use vegetable oil, which usually comes from corn or soy. Some eateries use partially hydrogenated vegetable oil for deep frying because they don't have to change it as often as the other oils, notes the Mayo Clinic. Partially hydrogenated oil contains trans fat, which raises the risk of heart attacks, strokes and Type 2 diabetes. Still other restaurants may use peanut oil or canola oil for frying.
One of the findings of a January 2012 study featured in the British Medical Journal is that the choice of cooking oil for frying can make a difference. A few studies have linked the higher consumption of fried foods with an elevated risk of cardiovascular disease, unhealthy lipids, obesity and a larger waist circumference, state the authors.
After assessing the participants' dietary habits and monitoring their medical records for 11 years, the researchers found no link between eating fried foods and the development of heart disease.
Why were the British Medical Journal study results at odds with previous research? The difference may lie in the type of fat used in frying. In Mediterranean countries, such as Spain, where the study was conducted, olive oil and sunflower oil are the most commonly used fats. Sixty-two percent of the participants in the study used olive oil. The results may not apply to other countries where other fats are used for frying, say the authors.
Healthy Oil Cooking Guidelines
The American Heart Association (AHA) provides a list of "better for you" fats that includes peanut, corn, olive, safflower, canola, soybean and sunflower oils. Other acceptable choices involve combinations of these oils in vegetables oils, as well as avocado, grapeseed, sesame seed and rice bran oils. The main thing to remember is to avoid hydrogenated and trans fats.
All the AHA-approved oils are suitable for home baking and cooking, including stir-frying and pan-frying. However, the organization doesn't recommend deep frying as a healthy cooking method.
Harvard Health Publishing agrees that sauteing is a healthier cooking method than deep frying. When food is immersed in oil, it absorbs more calories.
An August 2016 study published in Toxicology Reports found that reusing oil is also a threat to wellness. Filling up a deep-fryer with oil and using it only once can be expensive. To save money, some people save used cooking oil and fry with it repeatedly before disposal. The researchers found this practice creates free radicals, which have adverse health effects, including increasing the risk of cancer.
Sunflower Oil for Cooking
The Centers for Disease Control and Prevention and the AHA include sunflower oil in the list of heart-healthy oils. It's high in unsaturated fatty acids, which makes it a better alternative to saturated fat sources such as lard, palm oil, stick margarine and shortening. The medical community sanctions the use of sunflower oil for cooking or baking.
Consumers should be aware that findings from studies exploring the effects of sunflower oil aren't all positive. A February 2017 study published in the_ Journal of Hazardous Materials_ compared the aldehyde emissions of sunflower oil, canola oil, palm oil and soybean oil. Aldehydes are a concern because some of them are carcinogenic. Of the four oils, sunflower had the highest emissions, while palm and canola oil had the lowest.
The main possible side effect connected to sunflower oil is inflammation. Sunflower oil, in addition to corn, soy, safflower and vegetable oil, contains omega-6 fatty acids, which promote inflammation, warns the Arthritis Foundation. The organization doesn't advocate avoiding these oils, but it says not to overdo your intake.
Extra-Virgin Olive Oil Benefits
Based on the Acta Scientific Nutritional Health study, the best oil for frying chicken and making french fries is extra-virgin olive oil because it produces the least amount of harmful compounds when heated. Although deep frying isn't a cooking method health authorities recommend, on occasions when you have a yen for fried food, opt for this oil.
That extra-virgin olive oil carries anti-inflammatory properties is another reason why it's a good choice for cooking. Unlike sunflower, corn, safflower, soy and vegetable oils, all of which contain inflammatory omega-6 fatty acids, according to the Arthritis Foundation, olive oil is low in omega-6 fat. Harvard Health Publishing includes the capacity to reduce inflammation in its list of health benefits linked to olive oil. For this reason, olive oil is better than sunflower oil for cooking.
Read more: What Are the Benefits of Drinking Olive Oil?
In addition, olive oil is associated with other advantages. The National Cancer Institute states that research shows olive oil may also help protect against various cancers and cardiovascular disease. The prevention may stem from the oil's content of monounsaturated fat, phenols and vitamins E and F.
- Acta Scientific Nutritional Health: "Evaluation of Chemical and Physical Changes in Different Commercial Oils During Heating"
- University of Rochester Medical Center: "Cooking Oils: Which One When, and Why?"
- Mayo Clinic: "Trans Fat Is Double Trouble for Your Heart Health"
- British Medical Journal: "Consumption of Fried Foods and Risk of Coronary Heart Disease: Spanish Cohort of the European Prospective Investigation Into Cancer and Nutrition Study"
- American Heart Association: "Healthy Cooking Oils"
- Harvard Health Publishing: "Healthier Oils Make Fried Food Safer"
- Toxicology Reports: "Evaluation of the Deleterious Health Effects of Consumption of Repeatedly Heated Vegetable Oil"
- Centers for Disease Control and Prevention: "Keep Your Heart Healthy"
- Journal of Hazardous Materials: "Effects of Cooking Method, Cooking Oil, and Food Type on Aldehyde Emissions in Cooking Oil Fumes"
- Arthritis Foundation: "Fats and Oils to Avoid"
- Harvard Health Publishing: "Is Extra-Virgin Olive Oil Extra Healthy?"
- National Cancer Institute: "Olive Oil"
- What's Cooking America: Types of Cooking Fats and Oils
- National Sunflower Association: What is High Oleic Sunflower Oil?