The vitamin E content in canola and other oils may be to blame for the rising incidence of inflammation and asthma, researchers believe.
The new study shows drastically different health effects of vitamin E depending on its form. The form of Vitamin E called gamma-tocopherol in the ubiquitous soybean, corn and canola oils is associated with decreased lung function in humans, the study reports.
The other form of Vitamin E, alpha-tocopherol, which is found in olive and sunflower oils, does the opposite. It associated with better lung function.
This is the first study to show gamma-tocopherol is associated with worse lung function.
The study examined 4,526 individuals from the Coronary Artery Risk Development in Young Adults Study (CARDIA). Cook-Mills had done previous allergy research in mice showing alpha-tocopherol decreased lung inflammation, protecting healthy lung function and gamma-tocopherol increased lung inflammation and airway hyperresponsiveness, a characteristic of asthma. She hypothesized that they might have similar effects in humans.
Cook-Mills examined the CARDIA results for individuals' lung function tests at four intervals from baseline to 20 years and the type of tocopherol levels in their blood plasma at three intervals from baseline to 15 years. She found that a high level of gamma-tocoperol, 10 micromolar in the blood plasma, was associated with a 10 to 17 percent reduction in lung function. Micromolar is a measure of the amount of gamma-tocopherol per liter volume of blood plasma.
"The blood plasma showed how much they had acquired in their tissues," Cook-Mills said. "You get vitamin E from your diet or supplements."
The study has been published in the journal Respiratory Research.