The effect of vitamin E on lung health may depend on its form

A new US study suggests that the form of vitamin E called gamma-tocopherol, found in soybean, corn and canola oils, is associated with decreased lung function, while alpha-tocopherol, contained in olive and sunflower oils, does support lung function.

The observational study examined the lung function and measured the concentrations of vitamin E, alpha- and gamma-tocopherol, in the blood plasma of 4,526 adults at several points in time over 20 years (1). The study results showed that a high level of gamma-tocoperol, 10 micromolar in blood plasma, was associated with a 10 to 17% reduction in lung function – a reduced lung capacity found in an asthmatic condition. Parti- cipants with asthma and high gamma-tocopherol levels had the lowest lung function.

The researchers commented that earlier research in animals showed that gamma-tocopherol seems to incre- ase lung inflammation and airway hyperresponsiveness, a characteristic of asthma (2). On the other hand, alpha-tocopherol decreased lung inflammation, protecting healthy lung function. The effects on inflammation seem to be linked to an enzyme (protein kinase C-alpha), which binds both forms of vitamin E: while alpha-tocopherol inhibits the action of the protein, gamma-tocopherol increases its action. Both forms, which are the most abundant vitamin E forms in diet and tissues, may have similar effects in humans. Asthma is a complex dysfunction, involving over 90 genes. Many factors can initiate a reaction, including allergens and environmental irritants like smoke particulates.

Considering the rate of affected people found in this study, there could be 4.5 million individuals in the US with reduced lung function as a result of their high gamma-tocopherol consumption, the researchers con- cluded. Rates of asthma in the US have been climbing in the last 40 years, coinciding with a switch in US diets from lard and butter to gamma-tocopherol-rich soybean, canola and corn oils. Looking at other count- ries’ rates of asthma, those with significantly lower rates of asthma have diets high in olive and sunflower oils (3). In the US, the average blood plasma level of gamma-tocopherol is four or more times higher than those of European and Scandinavian countries that consume sunflower and olive oil.

1. Marchese M. E. et al. The vitamin E isoforms alpha-tocopherol and gamma-tocopherol have opposite associations with spirometric parameters: the CARDIA study. Respir Res. 2014; 15:31.
   
2. Berdnikovs S. et al. Isoforms of vitamin E have opposing immunoregulatory functions during inflammation by regulating leukocyte recruitment. J Immunol. 2009; 182(7):4395–4405.
   
3. Cook-Mills J. M. et al. Two faces of vitamin E in the lung. Am J Respir Crit Care Med. 2013; 15:279–284.