No link between vitamin and antioxidant intake and asthma status: Japan RCT
This was the key finding from a study assessing the relationships between oxidative stress, serum vitamin levels, dietary vitamin intake, daily physical activity, and pulmonary functions in asthma patients.
The study assessed 18 patients with bronchial asthma, testing their oxidative stress levels, antioxidant capacity, respiratory functions, serum vitamin levels, pulmonary functions, and daily level of physical activity.
It found “no significant relationships between the index of oxidative stress and pulmonary functions, levels of vitamin in serum, daily vitamin intakes, and activity counts in asthmatic patients”.
Though several earlier studies had shown antioxidants to benefit pulmonary functions and asthmatic symptoms, little to no relation between oxidative stress markers and either vitamins in serum or the daily intake of vitamins was found.
"Therefore, no clear and obvious relationships may exist in antioxidant vitamins or nutrition in a real-life setting," wrote the researchers.
Although vitamin D is not an antioxidant, the study also assessed the subjects' vitamin D levels. Previous studies have linked vitamin D deficiency to deteriorated lung function in asthma patients, while higher levels have been found to protect against exacerbation.
But in this case, the researchers wrote: "We could not find any correlation between pulmonary functions and either the serum levels or intake of vitamin D. The protective effects with exacerbation were not observed because of the short period of this study."
Additionally, α-tocopherol and γ-tocopherol, both variants of vitamin E, were measured in the patients. The former was found to be slightly above the normal range and the latter within normal range.
A previous study had reported that low levels of α-tocopherol and high levels of γ-tocopherol increase the risk of asthma, though “further study is necessary to clarify the relationships between α-tocopherol and γ-tocopherol in patients with established asthma”.
The reseachers concluded: "In a real life setting with a short-term evaluation, oxidative stress may not be affected by daily activity and by antioxidant nutrition intake. A large and longitudinal prospective study is necessary to confirm our results."
Source: Yonago Acta Medica
“Relationship between Oxidative Stress, Physical Activity, and Vitamin Intake in Patients with Asthma”
Authors: Akira Yamasaki, et al.