Vitamin E in Canola and Other Oils Found to Hurt Lungs

alpha- and gamma-tocopherol structures
Vitamin E molecules alpha- and gamma-tocopherol. The difference is the extra methyl group (CH3) on the first ring. Credit: Todd Helmenstine

Vegetable oils were added to our diets as an alternative to cooking with lard and butter, which are believed to be healthier for the heart. These oils also contain the antioxidant vitamin E molecule tocopherol for an additional nutritional benefit. Different oils have different forms of vitamin E. Olive, sunflower, and safflower oils contain the alpha-tocopherol form and canola, soybean and corn oils contain the gamma-tocopherol form. Alpha-tocopherol oils are more popular in European countries where gamma-tocopherol oils are used more in the United States.

A new study from Northwestern University’s Northwestern Medicine shows the slight difference between these two molecules makes a strong difference in lung function. Asthma rates in the United States have been climbing steadily for the past 40 years, coinciding with the switch from cooking with lard and butter to gamma-tocopherol vegetable oils. European countries switched to alpha-tocopherol vegetable oils and have significantly less of an asthma problem.

In lab animals, alpha-tocopherol was found to promote lung function where gamma-tocopherol decreased lung-function. The researches wanted to see if the same is true for humans. They examined 20 years of data from individuals involved in the Coronary Artery Risk Development in Young Adults (CARDIA) study. The researchers found that a 10 micromolar concentration of gamma-tocopherol in blood plasma yielded a 10 to 17% reduction in lung function. A 10% reduction in lung function is similar to an asthma attack.

Americans were found to have four or more times the levels of gamma-tocopherol in their blood plasma than Europeans. “Considering the rate of affected people we found in this study, there could be 4.5 million individuals in the U.S. with reduced lung function as a result of their high gamma-tocopherol consumption,” said senior author Joan Cook-Mills.

If you suffer from asthma or other breathing difficulties, perhaps a change in your cooking oil of choice would help.