Scientists say fast food can raise a teen's risk of developing asthma by nearly 40 percent. The findings come after an international study involving children in 31 countries.
Fast food can significantly increase the chances of developing asthma, eczema and rhinitis for children, according to the study published in the respiratory journal Thorax.
Teenagers who eat three or more weekly servings of fast food are said to have a 39 percent increased risk of developing severe asthma. The increased risk for children aged between six and seven is 27 percent.
The researchers say that youngsters who ate more fruit and vegetables during the study were less likely to be at a higher risk of getting asthma or allergies.
But Professor Luis Garcia-Marcos, one of the authors of the latest findings, says there are other important factors apart from fast food.
"The most important point is that this is all over the world," explains Garcia-Marcos, adding that the increased risk "is related to the westernization and Mcdonaldization of the world."
Scientists have been studying children for the International Study of Asthma and Allergies in Childhood (ISAAC) since 1994 – a research project involving close to two million children in more than 100 countries.
"Fast food" can mean different things in different countries - some options are healthier than others
For the latest results, Spaniard Garcia-Marcos and other researchers from Germany, New Zealand, Australia and the UK studied children in countries as different as Australia and Zambia. Their study is the first to link asthma to diet in both rich and poor countries - previous studies have mostly focused on the West.
Obesity linked to asthma
The link between asthma and fast food – rich in carbohydrates and trans fatty acids – has long been suspected by physicians, who have also observed that obese asthmatics are likely to have more severe symptoms than other sufferers. And that's why some physicians advise asthmatics to avoid food rich in the trans fats found in fast food.
But fast food has changed significantly in the past ten years.
People are just as likely to grab a smoothie or salad as a take away.
Professor Bernhard Watzl, a nutrition expert at the Max Rubner Institute, says however that "children who have fast food are more likely to eat unhealthily at home." Most, says Watzl, are more likely to eat animal products and carbohydrates.
In western countries, children in poor families are less likely to eat fruit and vegetables due to the rising cost of such food items. This development has been cited as an indicator of the rise in western lifestyles around the world – with even people in India consuming more meat than 20 years ago.
The incidence of asthma has increased almost in line with the rising rates of obesity. Obesity has been linked to chronic obstructive pulmonary disease (COPD). Both asthma and COPD are inflammatory diseases, so there is a good chance that they could also be linked to a higher risk of developing asthma, says Watzl. Although Watzl notes that other factors also play a role, including smoking and a lack of exercise.
What the study means for public health
Garcia-Marcos and his fellow researchers are hoping that their findings will lead to changes in the way we treat food.
"If the associations between fast foods and the symptom prevalence of asthma, rhinoconjunctivitis and eczema [are] causal, then the findings have major public health significance owing to the rising consumption of fast foods globally," the researchers say in a joint statement on the ISAAC website.
Some public authorities have already begun addressing the issue with restrictions on what can be served publicly.
California, for instance, banned trans fats in public restaurants in January 2010 – it was the first US state to do so. New York City then became the first to restrict the sale of large sugary drinks when it banned them last September. The US has the highest incidence of obesity in the world.
But Watzl says similar measures would not work in Germany - one of Europe's fattest countries.
"The US is more standardized. In Europe, the food environment is less standardized, so the regulations can't be the same," he says.
Teaching children about healthy food, says Watzl, is the best solution.