More fruit could mean less asthma in adults

By Stephen Daniells
5/17/2006

http://www.nutraingredients-usa.com/news/ng.asp?n=67753&m=2niu517&c=qdrhrvoeraoqydo

People with an antioxidant-rich diet could reduce
their risk of developing asthma in adulthood, say
Cambridge researchers - adding to a growing body of
science on the subject.

�We have found symptomatic asthma in adults to be
associated with a low intake of the dietary
antioxidants vitamin C and manganese. The low intake
of vitamin C appears to primarily associated with a
diet deficient in fruit,� wrote corresponding author
Dr. Nick Wareham.

This study appears to support a growing body of
science that has linked antioxidant intake,
particularly vitamins C and E, to the incidence of
asthma, a condition on the rise in the Western world
and the most common long-term condition in the UK
today. And, according to the charity Asthma UK, it
affects over four million adults and over a million
children.

According to the European Federation of Allergy and
Airway Diseases Patients Association (EFA), over 30m
Europeans suffer from asthma, costing Europe �17.7bn
every year. The cost due to lost productivity is
estimated to be around �9.8bn.

The new study, published in the journal Thorax (Vol.
61, pp. 388-393), used a nested case-control design to
investigate a potential relationship between fruit and
vegetable intake, and corresponding antioxidant
intake, and the incidence of both diagnosed and
symptomatic asthma for 515 cases and 515 controls with
average age 32.

The researchers used registrants in the European
Prospective Investigation of Cancer (EPIC)-Norfolk
cohort and assigned them as either cases or controls
depending on results from a health and lifestyle
questionnaire (HLQ). Dietary data was obtained using
seven day food diaries.

Dr. Wareham and his colleagues found that dietary
intake of vitamin C and manganese were inversely and
independently linked to symptomatic asthma, with a 12
per cent reduction in incidence with increasing
vitamin C intake, and a 15 per cent reduction in
incidence with increasing manganese intake. The
researchers divided intakes into five groups
(quintiles) ranging from low to high intake, but no
quantification of each cut-off point is made.

For diagnosed asthma, only manganese has an effect on
the incidence of the condition. Increasing intake of
manganese, as a per quintile measure, was associated
with a 14 per cent reduction in the risk of diagnosed
asthma.

When the researchers looked at the incidence and
associated risks of both symptomatic and diagnosed
asthma in terms of fruit and vegetable consumption,
and particular types of each, it was reported that
moderate consumption (between 0.7 and 46.2 grams per
day) of citrus fruits decreased the risk of asthma by
12 per cent. High consumption (46.3 grams per day or
more) decreased the risk by 41 per cent.

Apples consumption also reported a significant effect
on the risk of asthma, both symptomatic and diagnosed,
with high consumption (48.1 grams per day or more)
associated with a 32 per cent reduction in risk.

�Our observations are consistent with previous
reports
of an inverse association between dietary fruit and
dietary vitamin C and respiratory symptoms,� said
the
researchers.

The mechanism behind the protective effects of vitamin
C and manganese appears to be due to their antioxidant
nature, with manganese in particular playing a key
role in the enzyme superoxide dismutase. Reduced
levels of this enzyme have been reported in the lungs
and blood of asthma sufferers.

A major strength of this study, argue the researchers,
is the comprehensive nature of the dietary data,
allowing them to confidently make the link between
manganese and vitamin C intake and reduced risk of
asthma.

There are several limitations however, as there are
with all observational studies. The most notable being
that cases may have altered their diets because of
their asthma, although possible errors from this are
reduced by the fact that only 22 cases reported such a
change. There also exists the possibility that other,
unaccountable confounders, may have affected the
results.

The study does appear to add to a growing body of
evidence linking increased antioxidant intake to a
reduced risk of asthma. Indeed, a spokesperson for
British charity Asthma UK told NutraIngredients.com:
"Fresh fruit and vegetables are a good source of
anti-oxidants and the results of several studies
suggest that a diet high in anti-oxidants may protect
against asthma and some other lung diseases.

This research has looked at whether people with a low
intake of fruit and antioxidants such as vitamin C
have a higher risk of asthma. Further research is
necessary before the link between diet and asthma is
fully understood.

However, Asthma UK would encourage all people with
asthma to strive towards general good health through
eating a healthy diet made up of plenty of fruit and
vegetables," they said.