A new US review suggests that adequate intakes of vitamin E (alpha-tocopherol, but not gamma-tocopherol) seem to help patients with chronic allergic inflammation of airways.
The review discussed the potential cellular mechanisms and differential effects that vitamin E forms alpha- and gamma-tocopherol had on the allergic inflammation of airways, providing a potential explanation for conflicting study results on the vitamin E forms’ protective role in asthma (1). The data analysis showed that the discrepancies in clinical studies are consistent with experimental evidence of differential regulatory acti- vity of the two tocopherol forms. In addition to their high antioxidant capacity, both tocopherols seem to regulate signaling pathways which are essential in the inflammatory process. Specifically, supplementation with physiological amounts of alpha-tocopherol has shown to have an anti-inflammatory effect, improving lung function in asthma patients, while gamma-tocopherol promotes inflammation.
The researchers commented that understanding the differential regulation of inflammation by these vitamin E forms would provide a basis for designing diets that help patients with chronic inflammatory airways more effectively. Patients with asthma have shown to have reduced concentrations of alpha-tocopherol and vitamin C (ascorbic acid) in airway fluid (2, 3). Countries with the highest prevalence rate of asthma tend to have higher plasma levels of gamma-tocopherol (4). In the United States, for example, the average plasma gam- ma-tocopherol levels are two to five times higher than those of many European and Asian countries, given that vitamin E in the US diet mainly comes in the form of gamma-tocopherol from soybean oil, the major dietary vegetable oil in the US. Alpha-tocopherol – the most biologically active vitamin E form reaching ten- fold higher tissue levels compared to other tocopherols – is mainly found in sunflower and olive oil, common- ly used across Europe.
Asthma is one of the world’s most common chronic diseases, with a conservative estimate of 300 million people being affected by it. Typical symptoms include chronic inflammation of the airways, periodic wheezing, breathlessness, paroxysmal cough, and chest tightness. Severity ranges from occasional symptoms to disab- ling persistent symptoms and/or frequent life-threatening exacerbations. Asthma is caused by a combination of genetic and environmental factors. Among the potential mechanisms that contribute to airway disease is an imbalance of oxidants and antioxidants (oxidative stress) (5).