A new study from King's College London and the University of
Nottingham has found an association between the amount of vitamin E in the
body, exposure to particulate pollution and lung function. The paper adds to
growing evidence from previous studies suggesting that some vitamins may play a
role in helping to protect the lungs from air pollution. Although the new study
did not specifically demonstrate a protective effect, it is the first to show a
clear link between vitamin E concentrations in the blood and exposure to fine
particulate pollution in the general population.
Particulate matter (PM) is one of the main air pollutants thought
to be damaging to human health. Previous studies have reported an inverse
association between exposure to PM and lung function. However, the underlying
mechanisms linking ambient air pollution to lung function are not yet fully
understood.
The new data, published in the American Journal of
Respiratory and Critical Care Medicine, looked at the association between
lung function and a set of metabolites -- chemical signatures circulating in
the blood -- and between these metabolites and exposure to PM10 and PM2.5
(particles smaller than 10 and 2.5 microns, respectively) determined as the
concentrations of these pollutants at the participants' residence.
Two-hundred and eighty metabolites were measured in the
blood of over 5,500 fasting volunteers from the TwinsUK study who had also
undergone a spirometry or lung test. This test determines the lung's forced
vital capacity (FVC), a measure of the amount of air you can exhale with force
after you inhale as deeply as possible, and forced expiratory volume (FEV), a
measure of the amount of air you can exhale with force in one breath.
A subset of this group of twins -- around 500 participants
-- living in the Greater London area also had their long-term exposure to PM
estimated from their postcode using computer modelling of air pollution across
London. Participants completed a medical history and lifestyle questionnaire,
including questions on whether they took vitamin supplements.
The profiling revealed 13 metabolites significantly
associated with FVC, 10 of which were also identified for FEV. Of the
metabolites associated with lung function, eight were also significantly
associated with exposure to both PM2.5 and PM10. In all eight instances, a
higher exposure to PM was found to correlate with lower levels of the
metabolite and a lower FEV.
Among the eight metabolites identified were two well-known
antioxidants, alpha tocopherol or a-tocopherol (biologically active form of
Vitamin E) and a metabolite of ascorbic acid (Vitamin C) known as threonate.
Both compounds have previously been linked to lung function as well as exposure
to PM.
The strongest association both with PM2.5 and FEV was seen
with vitamin E. Individuals with a higher exposure to PM2.5 had significantly
lower levels of alpha-tocopherol and also had lower lung function. These
findings provide further evidence supporting the theory that PM damages lungs
through oxidative attack while alpha-tocopherol acts to minimise oxidative
injury.
Dr Ana Valdes, Reader at the University of Nottingham and
co-author of the study, explained: 'Our work builds on a number studies
exploring whether some vitamins can counteract the negative effect on lungs
caused by air pollution. More work is needed to establish whether antioxidant
supplements do indeed provide protection to the lungs in the general
population.'
Professor Frank Kelly, Head of the Environmental Research
Group at King's College London and co-author of the study, said: 'These new
findings are consistent with previous reports which observed lower levels of vitamin
E in people with lung conditions such as asthma. However, we do not yet fully
understand which types of particulate pollution specifically damage the lungs
or which vitamins best interfere with this pathway to reduce the level of
damage.'
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