Fast food may increase the severity of conditions such as asthma and eczema in children, a new study indicates.

According to a team of international scientists, these findings could have major implications for public health, due to the popularity of these types of foods.

The study involved over 319,000 13-14-year-olds from 51 countries and over 181,000 six and seven-year-olds from 31 countries. All were involved in the International Study of Asthma and Allergies in Childhood - the largest study of its kind which involves almost two million children in over 100 countries.

All of the participants and their parents were asked about the children's experiences of asthma, eczema and rhinoconjuntivitis, a condition which leads to a blocked or runny nose, along with watery and itchy eyes. They were also asked about their diets.

The study focused on the severity of symptoms in the previous year, as well as certain food types which were already known to either help protect or damage health. These included, fruit, vegetables, fish, cereals, milk, eggs and fast food.

Consumption was divided into three groups:
-Never
-Occasionally (once or twice a week)
-Three or more times a week.

The scientists found that children who ate fast food three or more times a week appeared to suffer more severe forms of allergic asthma, eczema and rhinitis (runny and/or itchy nose, sneezing).

In fact overall, fast food was the only type of food to show the same links in both age groups. According to the scientists, this indicates that ‘such consistency adds some weight to the possible causality of the relationship'.

In relation to the teenagers, fast food was linked to the severity of symptoms for all three conditions in all countries, irrespective of social status or gender.

In relation to the younger children, the link was not as definitive, but still strongly existed. The scientists suggested that this may be because younger children have less control over their diet, in other words, their parents will largely choose what they eat.

Among teenagers who ate three or more fast food meals a week, there was a 39% increased risk of severe asthma, while this figure for younger children was 27%.

The study did note however that fruit appeared to offer a protective effect against all conditions and in all age groups.

The scientists said that this is most likely because fast food contains high levels of saturated fatty acids and trans fats, which are known to have a detrimental effect on immunity. On the other hand, fruit is rich in antioxidants and other compounds which help boost immunity.

The team from the UK and New Zealand said that while their results do not prove cause and effect, further studies are warranted.

"If the associations between fast foods and the symptom prevalence of asthma, rhinoconjunctivitis and eczema is causal, then the findings have major public health significance owing to the rising consumption of fast foods globally," they added.

Details of these findings are published in the journal, Thorax.

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