12 January - 20 June 2016

Vitamin E in canola, soybean and corn oils can harm lungs

04 June 14

A first of its kind study by the Northwestern University School of Medicine has shown drastically different effects of vitamin E intake in humans depending on the form of the vitamin. Associations were observed between gamma-tocopherol levels in the blood - present in soybean, corn and canola oils - and lung inflammation, airway hyperresponsiveness and asthma. In contrast, alpha-tocopherol, the form of vitamin E found in olive, wheat germ, almond and sunflower oils, in the blood was associated with better lung function in humans.

Researchers analysed data from a large cohort of 4526 participants aged 18-30 from the Coronary Artery Risk Development in Young Adults Study (CARDIA). Senior author Joan Cook-Mills analysed spirometry data to measure lung function and capacity at 0, 2, 5, 10 and 20 years, and alpha and gamma tocopherol levels in the blood plasma at 0, 7 and 15 years.

The study concluded that high gamma-tocopherol levels were associated with a 10-17% reduction in lung function. Vitamin E affects lung function because it influences a protein that allows white blood cells to exit the bloodstream and enter tissues, including cells in the lung. Gamma-tocopherol increases the activity of the protein, causing lung inflammation, whereas alpha-tocopherol reduces it. Separate research on allergies has shown that in mice, alpha-tocopherol decreased lung inflammation and gamma-tocopherol increased airway hyperresponsiveness, a characteristic of asthma.

Cook-Mills noted that a 10% reduction in lung function is comparable to an asthmatic condition, causing trouble breathing and expelling air, reducing lung capacity. Therefore, these recent findings are significant for human health, with potential implications including improving lung capacity, improving and maintaining lung function and ultimately decreasing the incidence of individuals with reduced lung function.

Also significant is the potential link to diet. A movement in U.S diets away from lard and butter to oils such as soybean, canola and corn oils has coincided with elevated rates of asthma, though Dr Cook-Mills stressed that this is only observational at present, and it has not been demonstrated that dietary vitamin E of either type has a direct effect on lung function. European and Scandinavian countries have higher dietary intakes of the alpha-tocopherol rich vegetable oils, leading to average blood plasma levels of gamma-tocopherol being four times lower than in the US. [NYTimes, NorthWestern]

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