21 May 2014
Vitamin E in canola linked to asthma, lung inflammation
by Will Parker
A new study from Northwestern University shows the drastically different health effects of vitamin E depending on its form. The study authors say a vitamin E variant known as gamma-tocopherol - found in soybean, corn, and canola oils - was found to be associated with decreased lung function in humans. The researchers speculate that the widespread use of these products could be linked to the rising incidence of lung inflammation and asthma.
Interestingly, while gamma-tocopherol was associated with decreased lung function in humans, the other form of vitamin E, alpha-tocopherol, which is found in olive and sunflower oils, does the opposite. It is associated with better lung function.
The study was based on more than 4,000 individuals from the Coronary Artery Risk Development in Young Adults Study (CARDIA). The researchers examined the CARDIA results for individuals' lung function tests and the type of tocopherol levels in their blood plasma. They found that a high level of gamma-tocoperol (10 micromolar in the blood plasma) was associated with a 10-17 percent reduction in lung function.
Rates of asthma in the U.S. have been climbing in the last 40 years, coinciding with a switch in U.S. diets from lard and butter to soybean, canola, and corn oils, which were thought to be healthier for the heart. Looking at other countries' rates of asthma, the researchers found those with significantly lower rates of asthma have diets high in olive and sunflower oils.
"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 immunologist Joan Cook-Mills, a senior author on the study.
The study, appearing in the journal Respiratory Research, notes that in the U.S., the average blood plasma level of gamma-tocopherol is four or more times higher than those of European countries that consume sunflower and olive oil.
"People in countries that consume olive and sunflower oil have the lowest rate of asthma and those that consume soybean, corn and canola oil have the highest rate of asthma," Cook-Mills said. "When people consume alpha-tocopherol, which is rich in olive oil and sunflower oil, their lung function is better."
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Source: Northwestern University