Tuesday May 20, 2014 (foodconsumer.org) -- A new study led by scientists at Northwestern University suggests intake of vitamin E from canola oil, corn oil and soybean oil or dietary supplements can cause inflammation in the lungs and probably asthma as well while vitamin E in olive oil and sunflower oil protects against inflammation in the lungs.

These are two types of vitamin E, gamma-toccopherol found high in soybean oil, canola oil and corn oil and alpha-tocopherol found high in olive oil and sunflower oil.

The new study shows gamma tocopherol is associated with decreased lung function in humans while alpha tocopherol is associated with better lung function.

Dr. Joan Cook-Mills, senior author of the study, said as many as 4.5 million Americans may suffer reduced lung function as a result of consuming high gamma-tocopherol in soybean oil, canola oil and corn oil.

The study was presented in May at the Oxidants and Antioxidants in Biology World Congress and also published in the journal Respiratory Research.  

The study, the first of its kind, explains why the rate of asthma in the U.S. has been increasing in the past 40 years.  During the same period, Americans stopped using lard and butter and started using soybean, canola and corn oils.  Vegetable oils are considered healthier for the heart than animal fats like lard and butter.

Dr. Cook-Mills also said people in other countries who used gamma-tocopherol rich olive oil and sunflower oil were at lower risk of asthma.  Americans' blood levels of gamma-tocopherol were four or more times higher than that found in people in European and Scandinavian countries where olive oil and olive oil were commonly consumed, Dr. Cook-Mills said in a press release.

The 2010 asthma rate in the U.S. was 8.4% and the rate in other countries where olive oil and sunflower oil were used was much lower.

The study suggests that olive oil and sunflower oil are healthier than soybean oil, canola oil and corn oil when it comes to how they affect the lung function.

This study also suggests people with asthma should avoid using gamma-tocopherol rich vegetables or supplements.  And health-concerned people should use only alpha tocopherol rich oil or alpha tocopherol supplements. (David Liu)